Soil-applied Zn effect on soil fractions

The interaction of Zn with soil compartments influences its bioavailability and uptake by plants. In this study, rice and soybean were cultivated under greenhouse conditions with the aim of evaluating Zn bioavailability and fractionation in a clayey-textured Typic Hapludox as a function of Zn rates (4 or 8 mg kg 1 Zn). The experiment was conducted until grain filling. Two soil subsamples (t 1 and t 2 ) that referred to the seeding and flowering stages, were collected and compared with two single extraction schemes, DTPA (Zn DTPAt1 and Zn DTPAt2 ) and Mehlich-1 (Zn Mt1 and Zn Mt2 ) for Zn available contents. Zn fractionation was carried out with t 2 soil subsamples for the testing of the following fractions: exchangeable Zn (Zn Exc ), Zn bound to carbonates (Zn Carb ), Zn bound to organic matter (Zn OM ), Zn bound to oxides (Zn Oxi ) and residual Zn (Zn res ). Zn applied to soil increased the Zn concentration in labile fractions in decreasing order as follows: Zn Exc > Zn OM > Zn Carb . There was no difference between the lesser or unavailable fractions, Zn Oxi and Zn res, when there was no correlation between the rates either with total accumulated Zn in plants (Zna total ), or the contents extracted by DTPA or Mehlich-1. Total cumulative Zn content in rice and soybean affected by the ZnCl 2 rates applied were positively correlated with Zn content extracted by both solutions. Both extractant solutions presented positive correlation between available contents of Zn with Zn bound to labile fractions.

Soil-applied Zn effect on soil fractions

The interaction of Zn with soil compartments influences its bioavailability and uptake by plants. In this study, rice and soybean were cultivated under greenhouse conditions with the aim of evaluating Zn bioavailability and fractionation in a clayey-textured Typic Hapludox as a function of Zn rates (4 or 8 mg kg 1 Zn). The experiment was conducted until grain filling. Two soil subsamples (t 1 and t 2 ) that referred to the seeding and flowering stages, were collected and compared with two single extraction schemes, DTPA (Zn DTPAt1 and Zn DTPAt2 ) and Mehlich-1 (Zn Mt1 and Zn Mt2 ) for Zn available contents. Zn fractionation was carried out with t 2 soil subsamples for the testing of the following fractions: exchangeable Zn (Zn Exc ), Zn bound to carbonates (Zn Carb ), Zn bound to organic matter (Zn OM ), Zn bound to oxides (Zn Oxi ) and residual Zn (Zn res ). Zn applied to soil increased the Zn concentration in labile fractions in decreasing order as follows: Zn Exc > Zn OM > Zn Carb . There was no difference between the lesser or unavailable fractions, Zn Oxi and Zn res, when there was no correlation between the rates either with total accumulated Zn in plants (Zna total ), or the contents extracted by DTPA or Mehlich-1. Total cumulative Zn content in rice and soybean affected by the ZnCl 2 rates applied were positively correlated with Zn content extracted by both solutions. Both extractant solutions presented positive correlation between available contents of Zn with Zn bound to labile fractions.(AU)

Alleviation of aluminum and cadmium toxicity by biochar and its potential toxicity to sorghum / Mitigação da toxidez por alumínio e cádmio por biochar e seu potencial tóxico para o sorgo

Biochar has been used as an alternative in organic wastes management and to alleviate trace elements toxicity. The aim of this research was to use a rapid and simple test to detect the potential toxic effects of biochar and its ability to alleviate aluminum and cadmium toxicity to seeds and seedlings of Sorghum bicolor L. Two experiments were carried out in Petri dishes with two different biochars where sorghum seeds were exposed to aluminum (experiment 1) and cadmium (experiment 2) solutions. The experimental designs were completely randomized, with five doses of aluminum or cadmium in aqueous solution (0, 0.5, 1, 2, and 4 mmol/L of Al or Cd), combined with or without the addition of 0.25 g of biochar from sugarcane bagasse or from sewage sludge. Compared to treatments without biochar, in the treatments with biochar, higher seed germination rate and growth of sorghum seedlings were obtained. Moreover, the biochars were not toxic to sorghum and they decreased the toxicity of aluminum and cadmium, mainly the biochar from sewage sludge that presented higher pH and greater occurrence of functional groups in its particles.

O biochar tem sido utilizado como uma alternativa para o manejo de resíduos orgânicos e na remedição da toxidez por elementos traços. Objetivou-se com essa pesquisa usar um teste rápido e simples para detectar os potenciais efeitos tóxicos do biochar e sua capacidade de minimizar a toxidez por alumínio e cádmio para sementes e plântulas de Sorghum bicolor L. Conduziu-se dois experimentos em placas de Petri com dois diferentes biochars onde as sementes de sorgo foram expostas às soluções de alumínio (experimento 1) e cádmio (experimento 2). Os delineamentos experimentais foram inteiramente casualizados, com cinco doses de alumínio ou cádmio na solução aquosa (0, 0,5, 1, 2 e 4 mmol L-1 de Al ou Cd), combinados com ou sem a adição de 0,25g de biochar de bagaço de cana-de-açúcar (BB) ou de lodo de esgoto (BS). Nos tratamentos com biochar, obtém-se maior percentagem de germinação de sementes e crescimento de plântulas de sorgo em relação a ausência de biochar. Além disso, os biochars não são tóxicos para o sorgo e minimizam a toxicidade por alumínio e cádmio, principalmente o BS que apresenta maior pH e maior ocorrência de grupos funcionais em suas partículas.

Alleviation of aluminum and cadmium toxicity by biochar and its potential toxicity to sorghum / Mitigação da toxidez por alumínio e cádmio por biochar e seu potencial tóxico para o sorgo

Biochar has been used as an alternative in organic wastes management and to alleviate trace elements toxicity. The aim of this research was to use a rapid and simple test to detect the potential toxic effects of biochar and its ability to alleviate aluminum and cadmium toxicity to seeds and seedlings of Sorghum bicolor L. Two experiments were carried out in Petri dishes with two different biochars where sorghum seeds were exposed to aluminum (experiment 1) and cadmium (experiment 2) solutions. The experimental designs were completely randomized, with five doses of aluminum or cadmium in aqueous solution (0, 0.5, 1, 2, and 4 mmol/L of Al or Cd), combined with or without the addition of 0.25 g of biochar from sugarcane bagasse or from sewage sludge. Compared to treatments without biochar, in the treatments with biochar, higher seed germination rate and growth of sorghum seedlings were obtained. Moreover, the biochars were not toxic to sorghum and they decreased the toxicity of aluminum and cadmium, mainly the biochar from sewage sludge that presented higher pH and greater occurrence of functional groups in its particles.(AU)

O biochar tem sido utilizado como uma alternativa para o manejo de resíduos orgânicos e na remedição da toxidez por elementos traços. Objetivou-se com essa pesquisa usar um teste rápido e simples para detectar os potenciais efeitos tóxicos do biochar e sua capacidade de minimizar a toxidez por alumínio e cádmio para sementes e plântulas de Sorghum bicolor L. Conduziu-se dois experimentos em placas de Petri com dois diferentes biochars onde as sementes de sorgo foram expostas às soluções de alumínio (experimento 1) e cádmio (experimento 2). Os delineamentos experimentais foram inteiramente casualizados, com cinco doses de alumínio ou cádmio na solução aquosa (0, 0,5, 1, 2 e 4 mmol L-1 de Al ou Cd), combinados com ou sem a adição de 0,25g de biochar de bagaço de cana-de-açúcar (BB) ou de lodo de esgoto (BS). Nos tratamentos com biochar, obtém-se maior percentagem de germinação de sementes e crescimento de plântulas de sorgo em relação a ausência de biochar. Além disso, os biochars não são tóxicos para o sorgo e minimizam a toxicidade por alumínio e cádmio, principalmente o BS que apresenta maior pH e maior ocorrência de grupos funcionais em suas partículas.(AU)

Nitrogen as a mitigator of salt stress in yellow passion fruit seedlings / O nitrogênio como mitigador do estresse salino nas mudas de maracujazeiro amarelo

The poor chemical quality of water, especially in arid and semiarid regions, almost always precludes the practice of irrigated agriculture, thus demanding the adoption of techniques that mitigate the deleterious effects of excess salt on soil and plants. The aim of this research was to evaluate the effectiveness of nitrogen fertilization in mitigating the negative effects of excess salt in irrigation water on the growth of yellow passion fruit seedlings grown in a greenhouse in plastic tubes containing 0.65 dm3 of substrate. The treatments were organized in randomized blocks, in accordance with a 5 × 3 factorial scheme five electrical conductivities of irrigation water (0.3, 1.0, 2.0, 3.0, and 4.0 dS m-1) combined with three levels of nitrogen fertilizer (no nitrogen fertilization and 150 mg dm-3 of N derived from either ammonium sulfate or urea). Evaluations were performed 80 days after sowing and consisted of measuring the seedling height, stem diameter, number of leaves, leaf area, leaf nitrogen content, leaf concentration of chlorophyll a and b and total chlorophyll, specific leaf area, leaf area ratio, and Dickson quality index. An increase in the electrical conductivity of irrigation water hindered the production of yellow passion fruit seedlings. Nitrogen fertilization, with urea or ammonium sulfate, mitigated the effects of irrigation water salinity and favored the...(AU)

A baixa qualidade química da água, especialmente nas regiões áridas e semiáridas, quase sempre impede a prática da agricultura irrigada, exigindo a adoção de técnicas que atenuem os efeitos deletérios do excesso de sal no solo e nas plantas. O objetivo desta pesquisa foi avaliar a eficiência da adubação nitrogenada na mitigação dos efeitos negativos do excesso de sal na água de irrigação, sobre o crescimento de mudas de maracujazeiro amarelo, produzidas em tubetes contendo 0,65 dm3 de substrato em uma estufa telada. Os tratamentos, distribuídos em blocos ao acaso, obedeceu um esquema fatorial de 5 × 3 cinco condutividade elétrica da água de irrigação (0,3; 1,0; 2,0; 3,0; e 4,0 dS m-1) combinadas níveis de adubação nitrogenada (sem adubação nitrogenada e com aplicação 150 mg dm-3 de N utilizando sulfato de amônio ou ureia). As avaliações foram realizadas aos 80 dias após a semeadura e consistiram em medir a altura da muda, o diâmetro do caule, o número de folhas, a área foliar, o teor foliar de nitrogênio, os índices foliares de clorofila a e b e clorofila total, a área foliar específica, a razão de área foliar e o Índice de qualidade de Dickson. O aumento na condutividade elétrica da água de irrigação reduziu a qualidade das mudas de maracujazeiro amarelo. A adubação nitrogenada, com ureia ou sulfato de amônio, atenuou os efeitos da salinidade da água de irrigação...(AU)

Growth rates and yields of cassava at different planting dates in a tropical savanna climate

Details on growth and yield for cassava planted on different dates are useful for determining suitable genotypes for particular growing seasons. Our aim was to study growth and yield of cassava planted on different dates. Four cassava genotypes (Kasetsart 50, Rayong 9, Rayong 11 and CMR38-125-77) were evaluated using a randomized complete block design (RCBD) with four replications in six growing periods (20 Apr, 25 May, 30 June, 5 Oct, 10 Nov and 15 Dec 2015-2016) at Khon Kaen, Thailand. Soil properties were determined prior to planting, and crop traits and weather data were recorded. The six planting dates had a statistically significant effect on all crop traits. Low temperatures and solar radiation related to low biomass accumulation rates and short periods of linear phases for total crop and storage root dry weights with the 30 June planting date. CMR38-125-77 is likely to be a good genotype with respect to total crop and storage root dry weights at final harvest for almost all growing dates, except for the 20 Apr. Leaf area index (LAI) at 120, 240 and 300 days after planting (DAP), specific leaf area (SLA) at 120 DAP, storage root growth rate (SRGR) during 300-360 DAP and leaf growth rate (LGR) during 60-120 and 300-360 DAP were the components for the physiological determinants of total crop and storage root dry weight. The relationship between these physiological traits and storage root could be useful for cassava breeding.

Growth rates and yields of cassava at different planting dates in a tropical savanna climate

Details on growth and yield for cassava planted on different dates are useful for determining suitable genotypes for particular growing seasons. Our aim was to study growth and yield of cassava planted on different dates. Four cassava genotypes (Kasetsart 50, Rayong 9, Rayong 11 and CMR38-125-77) were evaluated using a randomized complete block design (RCBD) with four replications in six growing periods (20 Apr, 25 May, 30 June, 5 Oct, 10 Nov and 15 Dec 2015-2016) at Khon Kaen, Thailand. Soil properties were determined prior to planting, and crop traits and weather data were recorded. The six planting dates had a statistically significant effect on all crop traits. Low temperatures and solar radiation related to low biomass accumulation rates and short periods of linear phases for total crop and storage root dry weights with the 30 June planting date. CMR38-125-77 is likely to be a good genotype with respect to total crop and storage root dry weights at final harvest for almost all growing dates, except for the 20 Apr. Leaf area index (LAI) at 120, 240 and 300 days after planting (DAP), specific leaf area (SLA) at 120 DAP, storage root growth rate (SRGR) during 300-360 DAP and leaf growth rate (LGR) during 60-120 and 300-360 DAP were the components for the physiological determinants of total crop and storage root dry weight. The relationship between these physiological traits and storage root could be useful for cassava breeding.(AU)

Enrichment of population density of a bacterial consortium during bioremediation of a soil under successive contaminations with diesel oil / Enriquecimento da densidade populacional de um consórcio bacteriano durante a biorremediação de um solo sob sucessivas contaminações com óleo diesel

The effect of successive soil contamination with diesel oil was evaluated on population dynamics of a bacterial consortium (Acinetobacter baumannii LBBMA 04, Pseudomonas aeruginosa LBBMA 58, Ochrobactrum anthropi LBBMA 88b, Acinetobacter baumannii LBBMAES11, and Bacillus subtilis LBBMA 155) and on biodegradation of petroleum hydrocarbons (n-C12-C22). After each contamination with diesel oil, soil samples were collected for assessment of bacterial population and sequence of petroleum hydrocarbons degradation. At 20 and 40 days, the highest percentage of degradation was observed for the higher carbon chain hydrocarbons (n-C21 and C22). After the third contamination, there was a considerable reduction of n-C21degradation and a high degradation of hydrocarbons n-C13-15, C17 and C19, which contrasts with the low values of degradation of these hydrocarbons in the two previous phases. The highest growth rate of all members of the consortium occurred from 0 to 20 days, but population increase continued up to the end of the experiment (except for B. subitillis strain, whose population stabilized after 20 days). Our results show that the recurrent contamination by hydrocarbons affected the population structure of bacterial consortium and increased the total population density of the bacterial consortium.(AU)

O efeito da contaminação do solo com óleo diesel foi avaliado sobre a dinâmica populacional bacteriana de um consórcio (Acinetobacter baumannii LBBMA 04, Pseudomonas aeruginosa LBBMA 58, Ochrobactrum anthropi LBBMA 88b, Acinetobacter baumannii LBBMAES11 e Bacillus subtilis LBBMA 155) e sobre a biodegradação de hidrocarbonetos de petróleo (n-C12-C22). Após cada evento de contaminação com óleo diesel, foram coletadas amostras de solo para avaliação das populações bacterianas e da sequência de degradação de hidrocarbonetos de petróleo. Aos 20 e 40 dias, a maior porcentagem de degradação foi observada para os hidrocarbonetos de cadeia de carbono mais elevada (n-C21 e C22). Após a terceira contaminação, houve redução considerável da degradação de n-C21 e alta degradação dos hidrocarbonetos n-C13-15, C17 e C19, o que contrasta com os baixos valores de degradação desses hidrocarbonetos nas duas fases anteriores. A maior taxa de crescimento de todos os membros do consórcio ocorreu entre 0 e 20 dias, mas o aumento populacional continuou até o final do experimento (com exceção da linhagem B. subitilis, cuja população se estabilizou após 20 dias). Os resultados mostram que a contaminação sucessiva do solo com óleo diesel afetou a estrutura populacional do consórcio bacteriano e proporcionou aumento da densidade populacional total das bactérias.(AU)

Enrichment of population density of a bacterial consortium during bioremediation of a soil under successive contaminations with diesel oil / Enriquecimento da densidade populacional de um consórcio bacteriano durante a biorremediação de um solo sob sucessivas contaminações com óleo diesel

The effect of successive soil contamination with diesel oil was evaluated on population dynamics of a bacterial consortium (Acinetobacter baumannii LBBMA 04, Pseudomonas aeruginosa LBBMA 58, Ochrobactrum anthropi LBBMA 88b, Acinetobacter baumannii LBBMAES11, and Bacillus subtilis LBBMA 155) and on biodegradation of petroleum hydrocarbons (n-C12-C22). After each contamination with diesel oil, soil samples were collected for assessment of bacterial population and sequence of petroleum hydrocarbons degradation. At 20 and 40 days, the highest percentage of degradation was observed for the higher carbon chain hydrocarbons (n-C21 and C22). After the third contamination, there was a considerable reduction of n-C21degradation and a high degradation of hydrocarbons n-C13-15, C17 and C19, which contrasts with the low values of degradation of these hydrocarbons in the two previous phases. The highest growth rate of all members of the consortium occurred from 0 to 20 days, but population increase continued up to the end of the experiment (except for B. subitillis strain, whose population stabilized after 20 days). Our results show that the recurrent contamination by hydrocarbons affected the population structure of bacterial consortium and increased the total population density of the bacterial consortium.

O efeito da contaminação do solo com óleo diesel foi avaliado sobre a dinâmica populacional bacteriana de um consórcio (Acinetobacter baumannii LBBMA 04, Pseudomonas aeruginosa LBBMA 58, Ochrobactrum anthropi LBBMA 88b, Acinetobacter baumannii LBBMAES11 e Bacillus subtilis LBBMA 155) e sobre a biodegradação de hidrocarbonetos de petróleo (n-C12-C22). Após cada evento de contaminação com óleo diesel, foram coletadas amostras de solo para avaliação das populações bacterianas e da sequência de degradação de hidrocarbonetos de petróleo. Aos 20 e 40 dias, a maior porcentagem de degradação foi observada para os hidrocarbonetos de cadeia de carbono mais elevada (n-C21 e C22). Após a terceira contaminação, houve redução considerável da degradação de n-C21 e alta degradação dos hidrocarbonetos n-C13-15, C17 e C19, o que contrasta com os baixos valores de degradação desses hidrocarbonetos nas duas fases anteriores. A maior taxa de crescimento de todos os membros do consórcio ocorreu entre 0 e 20 dias, mas o aumento populacional continuou até o final do experimento (com exceção da linhagem B. subitilis, cuja população se estabilizou após 20 dias). Os resultados mostram que a contaminação sucessiva do solo com óleo diesel afetou a estrutura populacional do consórcio bacteriano e proporcionou aumento da densidade populacional total das bactérias.

Endozoochorous dispersal of seeds of weedy rice (Oryza sativa L.) and barnyardgrass (Echinochloa crus-galli L.) by cattle

ABSTRACT: The objective of this study was to evaluate endozoochory dispersal, recuperation, and germination of weedy rice (Oryza sativa L.) and barnyardgrass (Echinochloa crus-galli L.) seeds passed through the digestive system of cattle. The experiment was divided into two phases: first, the daily seed recuperation rate was determined after passing through the digestive system of six steers. Each animal was dosed individually with 1000 weedy rice seeds and 13,818 barnyardgrass seeds, and these seeds were subsequently collected from feces. In the second phase, seed germination and emergence rate after passing or not passing through the digestive system of cattle were determined in two types of substrates (fecal plaque and soil) in a 2×2 factorial design. Seed recuperation in feces showed sigmoid behavior with maximum recovery on the second day after dosage. The recuperation of the species in the feces was 50.9% and 23.4% for weedy rice and barnyardgrass, respectively, which shows that both have potential endozoochory dispersal. However, seed germination of these species reduced after they passed through the digestive system, and they presented inferior emergence in the fecal plaque compared to the soil. The quarantine period for animals that ingest weedy rice and barnyardgrass seeds should be at least 6 and 7 days, respectively.

RESUMO: O objetivo deste trabalho foi avaliar a dispersão endozoocórica, recuperação e germinação de sementes de arroz daninho (Oryza sativa L.) e capim-arroz (Echinochloa crus-galli L.) passadas pelo sistema digestivo de bovinos. O experimento foi dividido em duas fases: primeiramente determinou-se a taxa de recuperação diária das sementes após passagem pelo sistema digestivo de seis bovinos. Foram dosadas individualmente 1000 sementes de arroz daninho e 13818 sementes de capim-arroz para cada animal e posteriormente coletadas nas fezes. Na segunda fase foi determinada a taxa de germinação e emergência de sementes com e sem passagem pelo sistema digestivo de bovinos em dois tipos de substratos (placa fecal ou solo) em delineamento fatorial 2x2. A recuperação de sementes nas fezes apresentou comportamento sigmoide com máxima recuperação no 2° dia após dosagem. A recuperação nas fezes foi de 50,9% e 23,4%, para arroz daninho e capim-arroz, o que demonstra que ambas apresentam potencial de dispersão endozoocórica. Porém, a germinação de sementes destas espécies reduziu ao passar pelo sistema digestivo, e na placa fecal apresentou emergência inferior em comparação ao solo. O período de quarentena para animais que ingerirem sementes de arroz daninho e capim-arroz deve ser de no mínimo 6 e 7 dias, respectivamente.

Endozoochorous dispersal of seeds of weedy rice (Oryza sativa L) and barnyardgrass (Echinochloa crus-galli L) by cattle / Dispersão endozoocórica de sementes de arroz daninho (Oryza sativa L) e capim-arroz (Echinochloa crus-galli L) por bovinos

The objective of this study was to evaluate endozoochory dispersal, recuperation, and germination of weedy rice (Oryza sativa L.) and barnyardgrass (Echinochloa crus-galli L.) seeds passed through the digestive system of cattle. The experiment was divided into two phases: first, the daily seed recuperation rate was determined after passing through the digestive system of six steers. Each animal was dosed individually with 1000 weedy rice seeds and 13,818 barnyardgrass seeds, and these seeds were subsequently collected from feces. In the second phase, seed germination and emergence rate after passing or not passing through the digestive system of cattle were determined in two types of substrates (fecal plaque and soil) in a 2×2 factorial design. Seed recuperation in feces showed sigmoid behavior with maximum recovery on the second day after dosage. The recuperation of the species in the feces was 50.9% and 23.4% for weedy rice and barnyardgrass, respectively, which shows that both have potential endozoochory dispersal. However, seed germination of these species reduced after they passed through the digestive system, and they presented inferior emergence in the fecal plaque compared to the soil. The quarantine period for animals that ingest weedy rice and barnyardgrass seeds should be at least 6 and 7 days, respectively.(AU)

O objetivo deste trabalho foi avaliar a dispersão endozoocórica, recuperação e germinação de sementes de arroz daninho (Oryza sativa L.) e capim-arroz (Echinochloa crus-galli L.) passadas pelo sistema digestivo de bovinos. O experimento foi dividido em duas fases: primeiramente determinou-se a taxa de recuperação diária das sementes após passagem pelo sistema digestivo de seis bovinos. Foram dosadas individualmente 1000 sementes de arroz daninho e 13818 sementes de capim-arroz para cada animal e posteriormente coletadas nas fezes. Na segunda fase foi determinada a taxa de germinação e emergência de sementes com e sem passagem pelo sistema digestivo de bovinos em dois tipos de substratos (placa fecal ou solo) em delineamento fatorial 2x2. A recuperação de sementes nas fezes apresentou comportamento sigmoide com máxima recuperação no 2° dia após dosagem. A recuperação nas fezes foi de 50,9% e 23,4%, para arroz daninho e capim-arroz, o que demonstra que ambas apresentam potencial de dispersão endozoocórica. Porém, a germinação de sementes destas espécies reduziu ao passar pelo sistema digestivo, e na placa fecal apresentou emergência inferior em comparação ao solo. O período de quarentena para animais que ingerirem sementes de arroz daninho e capim-arroz deve ser de no mínimo 6 e 7 dias, respectivamente.(AU)

Simulation of soil water balance and partitioning of evapotranspiration of maize grown in two growing seasons in Southern Brazil / Simulação do balanço hídrico do solo e particionamento da evapotranspiração do milho cultivado em duas épocas de semeadura no Sul do Brasil

The objective of this study was to simulate the variation of the available soil water during maize crop growth, in two different sowing times (first and second growing season), using a drip irrigation system. The treatments consisted of different irrigation strategies (full to deficit). The SIMDualKc simulation model was used to determine the daily soil water balance and crop evapotranspiration using the dual crop coefficient approach. Soil, climate, crop and irrigation parameters were used as input data. Two experiments were carried out in a rainout shelter composed of two metallic structures (16x10m) in the city of Santa Maria, Rio Grande do Sul, Brazil, during 2010/11 (second crop, season 1) and 2011/12 (first crop, season 2) growing seasons, under no-tillage system. The simulations showed that all the irrigation management strategies used in season 2 resulted in soil water deficit, while only two strategies showed deficit in season 1. Results showed good agreement between observed and simulated soil water data, with an R2 ranging from 0.86 to 0.99 and the root mean square error ranging from 2.7 to 5.6% of the total available water for seasons 1 and 2, respectively. The observed results of water balance showed that maize grown in season 2 presented higher water consumption compared to season 1, due to the higher atmospheric demand of season 2. The SIMDualKc model allowed the partitioning of crop evapotranspiration into soil evaporation and crop transpiration, demonstrating that the vegetative growth subperiod presented the greatest differences between the two seasons compared to the others growth phases.

O objetivo deste estudo foi simular a variação da água disponível no solo durante o desenvolvimento da cultura do milho, em duas épocas de semeadura diferentes (primeira e segunda safra), utilizando sistema de irrigação por gotejamento. Os tratamentos consistiram em diferentes estratégias de irrigação (plena e deficitária). O modelo de simulação SIMDualKc foi utilizado para determinar o balanço hídrico diário do solo e a evapotranspiração da cultura usando a abordagem do coeficiente cultura dual. Os parâmetros de solo, clima, cultura e irrigação foram utilizados como dados de entrada. Dois experimentos foram realizados em uma cobertura móvel composta por duas estruturas metálicas (16x10m) na cidade de Santa Maria, Rio Grande do Sul, Brasil, nas safras 2010/11 (segunda safra, época 1) e 2011/12 (primeira safra, época 2), sob sistema de plantio direto. As simulações mostraram que todas as estratégias de manejo de irrigação usadas na época 2 resultaram em déficit hídrico, enquanto que apenas duas estratégias apresentaram déficit na época 1. Os resultados mostraram boa concordância entre os dados de água no solo observados e simulados, com um R2 variando de 0.86 a 0.99 e raiz quadrada do erro médio variando de 2,7 a 5,6% da água total disponível para as épocas 1 e 2, respectivamente. Os resultados observados do balanço hídrico mostraram que o milho cultivado na época 2 apresentou maior consumo de água em comparação com a época 1, devido à maior demanda atmosférica da época 2. O modelo SIMDualKc permitiu a partição da evapotranspiração da cultura em evaporação do solo e transpiração da cultura, demonstrando que o subperíodo de crescimento vegetativo apresentou as maiores diferenças entre as duas épocas em relação às demais fases de crescimento.

Simulation of soil water balance and partitioning of evapotranspiration of maize grown in two growing seasons in Southern Brazil / Simulação do balanço hídrico do solo e particionamento da evapotranspiração do milho cultivado em duas épocas de semeadura no Sul do Brasil

The objective of this study was to simulate the variation of the available soil water during maize crop growth, in two different sowing times (first and second growing season), using a drip irrigation system. The treatments consisted of different irrigation strategies (full to deficit). The SIMDualKc simulation model was used to determine the daily soil water balance and crop evapotranspiration using the dual crop coefficient approach. Soil, climate, crop and irrigation parameters were used as input data. Two experiments were carried out in a rainout shelter composed of two metallic structures (16x10m) in the city of Santa Maria, Rio Grande do Sul, Brazil, during 2010/11 (second crop, season 1) and 2011/12 (first crop, season 2) growing seasons, under no-tillage system. The simulations showed that all the irrigation management strategies used in season 2 resulted in soil water deficit, while only two strategies showed deficit in season 1. Results showed good agreement between observed and simulated soil water data, with an R2 ranging from 0.86 to 0.99 and the root mean square error ranging from 2.7 to 5.6% of the total available water for seasons 1 and 2, respectively. The observed results of water balance showed that maize grown in season 2 presented higher water consumption compared to season 1, due to the higher atmospheric demand of season 2. The SIMDualKc model allowed the partitioning of crop evapotranspiration into soil evaporation and crop transpiration, demonstrating that the vegetative growth subperiod presented the greatest differences between the two seasons compared to the others growth phases.(AU)

O objetivo deste estudo foi simular a variação da água disponível no solo durante o desenvolvimento da cultura do milho, em duas épocas de semeadura diferentes (primeira e segunda safra), utilizando sistema de irrigação por gotejamento. Os tratamentos consistiram em diferentes estratégias de irrigação (plena e deficitária). O modelo de simulação SIMDualKc foi utilizado para determinar o balanço hídrico diário do solo e a evapotranspiração da cultura usando a abordagem do coeficiente cultura dual. Os parâmetros de solo, clima, cultura e irrigação foram utilizados como dados de entrada. Dois experimentos foram realizados em uma cobertura móvel composta por duas estruturas metálicas (16x10m) na cidade de Santa Maria, Rio Grande do Sul, Brasil, nas safras 2010/11 (segunda safra, época 1) e 2011/12 (primeira safra, época 2), sob sistema de plantio direto. As simulações mostraram que todas as estratégias de manejo de irrigação usadas na época 2 resultaram em déficit hídrico, enquanto que apenas duas estratégias apresentaram déficit na época 1. Os resultados mostraram boa concordância entre os dados de água no solo observados e simulados, com um R2 variando de 0.86 a 0.99 e raiz quadrada do erro médio variando de 2,7 a 5,6% da água total disponível para as épocas 1 e 2, respectivamente. Os resultados observados do balanço hídrico mostraram que o milho cultivado na época 2 apresentou maior consumo de água em comparação com a época 1, devido à maior demanda atmosférica da época 2. O modelo SIMDualKc permitiu a partição da evapotranspiração da cultura em evaporação do solo e transpiração da cultura, demonstrando que o subperíodo de crescimento vegetativo apresentou as maiores diferenças entre as duas épocas em relação às demais fases de crescimento.(AU)

Chemical attributes of a remineralized Oxisol / Atributos químicos de um Latossolo remineralizado

Remineralizers are comminuted rocks that are applied to soil, and their use as an agricultural amendment was regulated in Brazil in 2013. However, mechanisms of action of these materials must be better known to enable them to be best used in agricultural fields. Soil chemical attributes of an Oxisol were monitored after the application of a diabase remineralizer. The increase in exchangeable Na observed was associated with the dissolution of the border of the plagioclase crystals where this element is highly concentrated (albite). Therefore, it was inferred that the time since the application of the remineralizer (1 to 2 years depending on the treatment) was not sufficient to exhaust this crystal volume. Unfortunately, the presence of several sources of Ca-containing minerals in the remineralizer did not allow to infer if the calcic nuclei was dissolving. An increase in effective cation exchange capacity was observed without the concurrent increase in the pH of the soil. The two non-exclusive hypotheses proposed to explain this result were that an extra surface charge has originated on the surface of the newly precipitated oxidic phases and/or from the dissolution of the remineralizer grains. Rapid precipitation of amorphous solids (as measured by the increase in Alo and Feo) would also explain the lack of increase in exchangeable Fe and Al despite the large amount of Al2O3(11.90%) and Fe2O3 (14.45%) in the remineralizer.(AU)

O uso de remineralizadores como insumo agrícola foi regularizado em 2013, mas seus mecanismos de ação precisam ser melhor conhecidos para viabilizar o manejo nos campos agrícolas. Atributos químicos de um Latossolo foram monitorados após remineralização com diabásio. O aumento de Na trocável foi atribuído à dissolução das bordas dos plagioclásios (albita) onde a concentração deste elemento é maior. Infelizmente, não é possível especular se o tempo decorrido desde a aplicação (um a dois anos, dependendo do tratamento) foi suficiente para solubilizar o núcleo cálcico (anortita) destes cristais, já que o remineralizador possui outros minerais fonte de Ca. Houve aumento da capacidade de troca catiônica efetiva sem aumento do pH. As hipóteses propostas para explicar este fenômeno são a precipitação de fases oxídicas amorfas e o aparecimento de cargas elétricas na superfície dos grãos do remineralizador durante sua dissolução. Apesar da concentração de Al2O3 do remineralizador (11,90%) e Fe2O3 (14,45%), não houve aumento destes elementos no complexo de troca, possivelmente por sua rápida precipitação em formas amorfas (Alo e Feo no solo).(AU)

Minjingu phosphate rock availability in low-pH highly weathered soil as affected by added salts

Concentrations and identity of ions in the soil solution may affect soil phosphorus (P) reactions and P availability. In this study, the magnitude of these reactions was evaluated following the application of Minjingu phosphate rock (MPR) combined with chloride and carbonate salts of Na and Ca within an incubation experiment. Twenty-one days later NaOH-P and HCl-P were determined. This investigation was undertaken with the aim of identifying the role of Ca-ion activity in the liquid phase on the solubilization of MPR and formation of insoluble Ca-P phases. The increase in pH was higher with Na2CO3 than with CaCO3, while both CaCl2 and NaCl resulted in slight decreases in pH. The dissolution of MPR was higher overall when MPR was applied singularly than for the combined application of the phosphate rock with salts of calcium or sodium after 60 days of incubation. Dissolution of MPR decreased as levels of CaCO3 or CaCl2 increased but the decrease was more pronounced in CaCO3-treated than in CaCl2-treated soils. Ca-ion activity in the liquid phase is the main factor responsible for the insolubilization of MPR and the formation of insoluble Ca-P phases (HCl P). The formation of Ca-P solid phases increased with the concentration of Ca-ions, and was governed by the pH and nature of the accompanying anion. For soils with low levels of exchangeable cations and where liming is a recommended intervention measure, Ca from lime will form insoluble P phases and reduce the dissolution of PR and P availability to plants.

Minjingu phosphate rock availability in low-pH highly weathered soil as affected by added salts

Concentrations and identity of ions in the soil solution may affect soil phosphorus (P) reactions and P availability. In this study, the magnitude of these reactions was evaluated following the application of Minjingu phosphate rock (MPR) combined with chloride and carbonate salts of Na and Ca within an incubation experiment. Twenty-one days later NaOH-P and HCl-P were determined. This investigation was undertaken with the aim of identifying the role of Ca-ion activity in the liquid phase on the solubilization of MPR and formation of insoluble Ca-P phases. The increase in pH was higher with Na2CO3 than with CaCO3, while both CaCl2 and NaCl resulted in slight decreases in pH. The dissolution of MPR was higher overall when MPR was applied singularly than for the combined application of the phosphate rock with salts of calcium or sodium after 60 days of incubation. Dissolution of MPR decreased as levels of CaCO3 or CaCl2 increased but the decrease was more pronounced in CaCO3-treated than in CaCl2-treated soils. Ca-ion activity in the liquid phase is the main factor responsible for the insolubilization of MPR and the formation of insoluble Ca-P phases (HCl P). The formation of Ca-P solid phases increased with the concentration of Ca-ions, and was governed by the pH and nature of the accompanying anion. For soils with low levels of exchangeable cations and where liming is a recommended intervention measure, Ca from lime will form insoluble P phases and reduce the dissolution of PR and P availability to plants.(AU)

Sistemas de Integração lavoura-pecuária-floresta (iLPF)- Experiências no Brasil / Systems integration crop-livestock-forest (ICLF) - Experiences in Brazil

Os sistemas de integração lavoura-pecuária-floresta são sustentáveis e a escolha do sistema adequado à determinada localidade depende das condições edafo-climáticas e da existência de infraestrutura para suprimento de insumos, armazenagem e escoamento da produção. A produtividade e a rentabilidade são três vezes maiores para a pecuária de corte e de 10 a 30% para as lavouras de grãos em relação aos sistemas tradicionais de produção. Por outro lado, observa-se nos sistemas mais complexos (com uso de componente arbóreo) o aumento do bem-estar animal e a mitigação de gases de efeito estufa.

appropriate system to a given locality depends on the soil and climatic conditions and the availability of infrastructure for input supply, storage and transportation of production. Productivity and profitability are three times higher for beef cattle and 10-30% for grain crops relative to traditional production systems. On the other hand it is observed in more complex systems (using the tree component) animal welfare increase and mitigation of greenhouse gases.

Sistemas de Integração lavoura-pecuária-floresta (iLPF)- Experiências no Brasil / Systems integration crop-livestock-forest (ICLF) - Experiences in Brazil

Os sistemas de integração lavoura-pecuária-floresta são sustentáveis e a escolha do sistema adequado à determinada localidade depende das condições edafo-climáticas e da existência de infraestrutura para suprimento de insumos, armazenagem e escoamento da produção. A produtividade e a rentabilidade são três vezes maiores para a pecuária de corte e de 10 a 30% para as lavouras de grãos em relação aos sistemas tradicionais de produção. Por outro lado, observa-se nos sistemas mais complexos (com uso de componente arbóreo) o aumento do bem-estar animal e a mitigação de gases de efeito estufa.(AU)

appropriate system to a given locality depends on the soil and climatic conditions and the availability of infrastructure for input supply, storage and transportation of production. Productivity and profitability are three times higher for beef cattle and 10-30% for grain crops relative to traditional production systems. On the other hand it is observed in more complex systems (using the tree component) animal welfare increase and mitigation of greenhouse gases.(AU)

Avaliação de ovinos naturalmente infectados por nematoides gastrintestinais sob pastejo intermitente em cultivares de Brachiaria brizantha

Objetivou-se avaliar a resposta de ovinos naturalmente infectados por nematoides gastrintestinais sob regime de pastejo com lotação intermitente em diferentes cultivares de Brachiaria brizantha. O experimento foi realizado na área experimental do Grupo de Estudos em Forragicultura, localizado no Campus de Macaíba da Universidade Federal do Rio Grande do Norte. O período experimental foi de 31/03/17 a 31/08/2017, que correspondeu a dois ciclos de pastejo. Os animais foram mantidos em sistema semi-intensivo com pastejo intermitente e suplementados. Foram utilizados 48 ovinos, sem padrão racial definido, com peso médio inicial de 19,04 kg ±0,96, distribuídos aleatoriamente em quatro piquetes compostos pelas cultivares Marandu, Xaraés, Piatã e Paiaguás. O delineamento foi o de blocos ao acaso com 12 repetições nos animais e dois blocos das cultivares. As variáveis fenotípicas avaliadas semanalmente foram, contagem de ovos por grama de fezes (OPG), coprocultura, volume globular (VG), FAMACHA©, pesagem e escore de condição corporal (ECC). A recuperação de larvas infectantes na pastagem e no solo, foram de acordo com a troca dos animais nos piquetes de pré e pós pastejo. As cultivares de B. brizantha avaliadas influenciaram a carga parasitária dos animais, que foram mistas e maciças com valores acima de 600 ovos/g independente da cultivar pastejada, havendo diferença significativa nesses valores entre as cultivares, variando de 635,71 (Xaraés) a 1422,2 (Marandu). Entre os ciclos de pastejo houve diferença no OPG dos animais mantidos na cultivar Marandu (999,1 e 1422,2), sendo maior em relação às demais. Na coprocultura foram encontrados os seguintes gêneros: Haemonchus sp., Trichostrongylus sp., Strongyloides sp., e Oesophagostomum sp. O Haemonchus sp. foi o gênero de maior prevalência (acima de 80%) nos animais de todas as cultivares e ciclos de pastejo. No primeiro ciclo de pastejo houve diferença no VG dos animais mantidos nas cultivares Piatã (25,96%) e Xaraés (22,51%), sendo que os mantidos nas demais cultivares apresentaram valores intermediários. Quanto ao FAMACHA, os animais permaneceram com maior frequência nos graus 1, 2 e 3, em ordem de importância no ciclo 1, porém no ciclo 2, a concentração com mais de 50% dos indivíduos foi no grau 1. Quanto ao peso dos animais, o grupo mantido na cultivar Xaraés diferiu das demais (P<0,05), com menores médias, nos dois ciclos (21,79 e 26,91 Kg). O ECC dos animais se concentrou em 3 no primeiro ciclo de pastejo e entre 3, 3,5 e 4 no segundo ciclo. As cultivares Marandu e Paiaguás apresentaram as maiores médias de larvas no pasto. A concentração de larvas foi encontrada no pré pastejo e na porção inferior. O primeiro ciclo de pastejo obteve maior contagem de larvas. Foi possível recuperar larvas de estágio de vida livre e infectante dos gêneros Haemonchus, Trichostrongylus e Strongyloides. Nas amostras do solo de todas as cultivares foi possível recuperar larvas de estágio de vida livre e infectante dos gêneros Haemonchus e Trichostrongylus. A área da cv. Marandu apresentou maiores médias de larvas de estágio de vida livre (5,37) e Haemonchus (0,53). No primeiro ciclo de pastejo houve maior contagem de nematoides nas amostras de solo quando comparado com o segundo, com exceção da cv. Marandu. Pode-se concluir que as cultivares B. Brizantha promovem condições distintas para o desenvolvimento e sobrevivência das fases de vida livre dos nematoides gastrintestinais de acordo com as características morfológicas. As cultivares Piatã e Xaraés promovem menores cargas parasitárias no ambiente e nos animais, porém a Marandu e a Paiaguás, proporcionam melhores condições nutricionais aos animais não havendo comprometimento das variáveis fenotípicas pela maior carga parasitária. As cultivares de Brachiaria brizantha Piatã, Xaraés, Marandu e Paiaguás podem ser recomendadas para sistemas de produção de ovinos em pasto.

The objective of this study was to evaluate the response of naturally infected sheep by gastrointestinal nematodes under intermittent grazing conditions in different Brachiaria brizantha cultivars. The experiment was carried out in the Experimental Area of the Group of Forage Research, located at the Macaíba Campus of the Federal Universidade of Rio Grande do Norte. The experimental period was from 03/31/17 to 08/31/2017, which corresponded to two cycles of grazing. The animals were kept in a semi-intensive system with intermittent grazing and supplemented. We used 48 sheep, with no defined racial pattern, with a mean initial weight of 19.04 kg ± 0.96, randomly distributed in four pickets composed of Marandu, Xaraés, Piatã and Paiaguás. The experimental design was a randomized block design with 12 replicates in the animals and two blocks of the cultivars. The phenotypic variables evaluated weekly were egg counts per gram of faeces (EPG), coproculture, globular volume (VG), FAMACHA©, weighing and body condition score (BCS). The recovery of infective larvae in the pasture and in the soil, were according to the exchange of the animals in the pre and post grazing pickets. The B. brizantha cultivars evaluated influenced the parasitic load of the animals, which were mixed and massive with values above 600 eggs/g independent of the grazed cultivar, with a significant difference in these values among the cultivars, varying from 635.71 (Xaraés) to 1422.2 (Marandu). Among the grazing cycles, there were differences in the EPG of the animals kept in the Marandu cultivar (999.1 and 1422.2), being greater in relation to the others. In the coproculture were found the following genera: Haemonchus sp., Trichostrongylus sp., Strongyloides sp., and Oesophagostomum sp. The Haemonchus sp. was the most prevalent genus (over 80%) in all cultivars and grazing cycles. In the first grazing cycle, there was difference in VG of the animals kept in the Piatã (25.96%) and Xaraés (22.51%) cultivars, and those maintained in the other cultivars showed intermediate values. As for FAMACHA, the animals remained more frequently in grades 1, 2 and 3, in order of importance in cycle 1, but in cycle 2, the concentration with more than 50% of the individuals was in grade 1. Regarding the weight of the animals , the group maintained in the Xaraés cultivar differed from the others (P <0.05), with lower mean values in both cycles (21.79 and 26.91 kg). The BCS of the animals was concentrated at 3 in the first grazing cycle and at 3, 3.5 and 4 in the second cycle. The cultivars Marandu and Paiaguás presented the highest averages of larvae in the pasture. The concentration of larvae was found in pre-grazing and in the lower portion. The first cycle of grazing obtained a higher count of larvae. It was possible to recover larvae of free and infecting life stages of the genera Haemonchus sp., Trichostrongylus sp. and Strongyloides sp. In soil samples from all cultivars, it was possible to recover larvae from the free-living and infecting stages of the genera Haemonchus sp. and Trichostrongylus sp. The cv. Marandu presented higher mean free-stage larvae (5.37) and Haemonchus sp. (0.53). In the first grazing cycle there was a higher count of nematodes in the soil samples when compared to the second, except for cv. Marandu. It can be concluded that B. Brizantha cultivars promote climatic conditions for the development and survival of the distinct life phases of the different gastrointestinal nematodes according to the morphological characteristics, influencing the parasitic load of the animals. However, all cultivars are recommended for grazing, since cultivars Piatã and Xaraés promote lower parasitic loads in the environment and in animals. And the cultivars Marandu and Paiaguás, even resulting in higher parasitic loads, gave better nutritional conditions to the animals without compromising the phenotypic variables.

MORFOFISIOLOGIA DE GRAMINEAS FORRAGEIRAS TROPICAIS CULTIVADAS SOB DIFERENTES SUPRIMENTOS HIDRICOS E CONDICOES EDAFOCLIMATICAS

Objetivou - se avaliar as trocas gasosas, o fluxo de biomassa e as características estruturais e de biomassa de cinco gramíneas forrageiras tropicais: Búffel ( Pennisetum ciliare (L.) Link ) cultivar Gayndah ; Paiaguás e Piatã ( Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster ); Massai e Tamani ( Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs ), implantadas em duas classes texturais de solo (arenosa e média) e supridas com diferentes regimes de irrigação . As gramíneas foram agrupadas em g êneros botânicos para a condução das análises estatísticas, sendo comparadas entre si nas fases de crescimento. No caso do capim - búffel, as informações foram agrupad as em períodos, sendo comparado o d esempenho da cultivar entre período de crescimento. As trocas gasosas foram conduzidas em três fases: estabelecimento, onde foi realizado um curso diário sob o regime de irrigação de 100% da Et 0 , e períodos seco e de transição seco/chuvoso quando o ensaio se deu em solo de textura arenosa ; e seco e chuvoso quando as avaliação foram realizadas em solo de textura média. As avaliações de fluxo de biomassa e características de biomassa e estruturais també m foram realizadas em três períodos , seguindo o mesmo des envolvimento das trocas gasosas . Com relação ao s resultados em solo de textura arenosa, o capim - búffel apresentou as melhores respostas morfofisiológicas e estruturais no período seco, com o maior acúmulo de forragem verificado no regime de 90% da Et 0 . Já no tocante aos capins Massai e Tamani observaram - se maiores taxas de senescência foliar e maior acúmulo de biomassa de colmo verde no capim - tamani e, a semelhança do capim - búffel, o nível de 90% da Et 0 favorece o desempenho das funções fisiológicas de sta, traduzindo em melhores características produtivas. No que se refere aos capins Paiaguás e Piatã , as melhores características morfofisiológicas, estruturais e de produção de biomassa de lâminas foliares foram verificadas no capim - piatã, especialmente p ela menor taxa de senescência foliar, das hastes e maior produção de lâminas foliares no regime de 30% da Et 0 no período seco. Já em relação aos resultados em solo de textura média, o capim - búffel apresentou as melhores respostas no período seco, como maio r eficiência no uso da água , ma ior relação lâmina foliar/colmo e número de folhas vivas, sendo observado que, no regime de 60% da Et 0 durante o período seco, favoreceu as melhores características estruturais e produtivas quando do início do período chuvoso . No tocante aos capins Massai e Tamani, o capim - massai apresentou comportamento semelhante nos períodos seco e chuvoso, principalmente pela reduzida taxa de senescência foliar e baixo alongamento das hastes, mostrando - se mais resiliente aos menores regime s de irrigação. Para os capins Paiaguás e Piatã, por sua vez, foi verificado maior eficiência no uso da água e maior produção de lâminas foliares na fase de estabelecimento no capim - piatã, característica morfofisiológica interessante para uso em sistemas d e baixo regime hídrico, além de apresentar menor biomassa de colmo e de forragem morta nos períodos seco e chuvoso. De maneira geral, os maiores registros dos parâmetros fisiológicos foram observados nos horários de maior intensidade luminosa, independente mente da cultivar e da classe de solo a que estavam implantadas, o que mostra elevada capacidade fotossintética das gramíneas forrageiras tropicais. De igual modo, o regime de 30% da Et 0 no período seco possibilitou a manutenção do status morfofisiológico das gramíneas sem ocasionar morte de perfilhos e perda do vigor da rebrotação com a entrada no período das águas.

The objective of this study was to evaluate the gas exchange, the biomass flow and the structural and biomass characteristics o f five tropical forage grasses: Búffel (Pennis etum ciliare (L.) Link) cv. Gayndah; Paiaguás and Piatã (Urochloa brizantha (Hochst. Ex A. Rich.) R.D. We bster); Massai and Tamani (Megathyrsus maximus (Jacq .) B.K. Simon & S.W.L. Jacobs), i mplanted in two soil texture classes (sandy and medium) and supplied wit h different irrigation regimes. The grasses were grouped in botanical genera to conduct the statist ical analyzes, being compared among t hemselves in the growth phases. In the case of the buffel grass, the information was grouped in periods, being compared the performance of the cul tivar between period of growth. The gas exchanges were conducted in three phases: establishment, where a daily course was performed under the 100% Et 0 irr igation regime, and dry and dry/ rainy transition periods when t he test occurred in sandy soil; a nd dry and rainy when the evaluations were pe rformed in medium texture soil. Biomass flow and biomass and structural characteristics were also evaluated in three periods, following the same development o f gas exchanges. Regarding the results in sandy soil, buffel grass had the best morphophysiological and structural responses in th e dry period, with the highest forage accu mulation verified in the 90% Et 0 regimen. Regarding the Massai and Tamani grasses, there was a higher leaf senescence rate and a higher accumulation of green stem biomass in the tall grass, and similar to the buffe l grass, the 90% level of Et 0 favors the performance of the physiological functions o f this, translating into better product ive characteristics. Regarding the Paiaguás and Piatã grasses, the best morphophysiological, structural and biomass characteristics of leaf blades were observed in the piatã grass, especially due to the lower foliar senescence rate, stems and greater folia r leaf production in the 30% Et 0 in the dry period. Regarding the results in medium textured soil, buffel grass presented the best r esponses in the dry period, such as higher water use efficiency, higher leaf/stem ratio and number of live leaves, and i t was observed that in the 60 % o f Et 0 during the dry season favored the best structural and productive characteristics at the beginning of the rainy season. Massai and Tamani grasses showed similar behavior in the dry and rainy seasons, mainly due to the reduced rate of leaf senescence and low elongation of the stems, which was more resilient t o the lower irrigation regimes. For Paiaguás a nd Piatã grasses, in turn, greater efficiency in the use of water and greater production of leaf blades in the stage of establishment in the piatã grass, an interesting morphophysiological characteristic for use in systems of low water regime were veri fied , besides presenting lower s tem biomass and dead forag e in the dry and rainy seasons. In general, the greatest records of physiological parameters were observed at the highest light intensity, independently of the cultivar and the soil class to which they were implanted, which shows high photosynthetic capacity of the tropical forage grasses. Likewise, the regime of 30% Et 0 in the dry season allowed the maintenance of morphophysiological status of grasses without causing tiller death and loss of regrowth vi gor with the entry into the water period