Magnesium supplementation alleviates drought damage during vegetative stage of soybean plants.

Our working hypothesis was that magnesium (Mg) supplementation modulates plant performance under low water availability and improves drought tolerance in soybean genotypes. Plants of Bônus 8579, M8808 and TMG1180 genotypes were grown under field conditions and subjected to three water stress treatments (control, moderate and severe stress) and three Mg levels [0.9 (low), 1.3 (adequate) and 1.7 cmolc dm-³ (supplementation)]. After 28 days of drought imposition, the growth parameters, osmotic potential, relative water content, leaf succulence, Mg content and photosynthetic pigments were assessed. In general, drought drastically decreased the growth in all genotypes, and the reductions were intensified from moderate to severe stress. Under adequate Mg supply, TMG1180 was the most drought-tolerant genotype among the soybean plants, but Mg supplementation did not improve its tolerance. Conversely, although the M8808 genotype displayed inexpressive responses to drought under adequate Mg, the Mg-supplemented plants were found to have surprisingly better growth performance under stress compared to Bônus 8579 and TMG1180, irrespective of drought regime. The improved growth of high Mg-treated M8808-stressed plants correlated with low osmotic potential and increased relative water content, as well as shoot Mg accumulation, resulting in increased photosynthetic pigments and culminating in the highest drought tolerance. The results clearly indicate that Mg supplementation is a potential tool for alleviating water stress in M8808 soybean plants. Our findings suggest that the enhanced Mg-induced plant acclimation resulted from increased water content in plant tissues and strategic regulation of Mg content and photosynthetic pigments.

Selection of Soybean and Cowpea Cultivars with Superior Performance under Drought Using Growth and Biochemical Aspects.

Identifying cultivars of leguminous crops exhibiting drought resistance has become crucial in addressing water scarcity issues. This investigative study aimed to select soybean and cowpea cultivars with enhanced potential to grow under water restriction during the vegetative stage. Two parallel trials were conducted using seven soybean (AS3810IPRO, M8644IPRO, TMG1180RR, NS 8338IPRO, BMX81I81IPRO, M8808IPRO, and BÔNUS8579IPRO) and cowpea cultivars (Aracê, Novaera, Pajeú, Pitiúba, Tumucumaque, TVU, and Xique-xique) under four water levels (75, 60, 45, and 30% field capacity-FC) over 21 days. Growth, water content, membrane damage, photosynthetic pigments, organic compounds, and proline levels were analyzed. Drought stress significantly impacted the growth of both crops, particularly at 45 and 30% FC for soybean and 60 and 45% FC for cowpea plants. The BÔNUS8579IPRO and TMG1180RR soybean cultivars demonstrated the highest performance under drought, a response attributed to increased amino acids and proline contents, which likely help to mitigate membrane damage. For cowpea, the superior performance of the drought-stressed Xique-xique cultivar was associated with the maintenance of water content and elevated photosynthetic pigments, which contributed to the preservation of the photosynthetic efficiency and carbohydrate levels. Our findings clearly indicate promising leguminous cultivars that grow under water restriction, serving as viable alternatives for cultivating in water-limited environments.

Efficiency of nitrogen and potassium application on phytotechnical parameters and yield of melon / Eficiência da aplicação de nitrogênio e potássio sobre caracteres fitotécnicos e rendimento do meloeiro

Phytotechnical parameters, yield and fertilizer use efficiency are relevant to the rational management of fertigation, especially in cultivation of high technological level. Thus, the objective was to evaluate the influence and efficiency of nitrogen (N) and potassium (K) application on the phytotechnical parameters, yield and nutritional efficiency of yellow melon in a fertigation system. The experiment was conducted in the city of Bom Jesus-PI, Brazil, from January to April 2016, in a strip-block design with four replicates, and the treatments consisted of five N levels (0, 45, 90, 135 and 180 kg ha-1 in the form of urea) and five K levels (0, 60, 120, 180 and 240 kg ha-1 in the form of potassium chloride), applied through fertigation. Collar diameter, main branch length, leaf chlorophyll content, number of leaves, leaf area index, biomass accumulation, fruit yield, and N and K use efficiencies were evaluated. Applications of 180 kg ha-1 of N and 240 kg ha-1 of K, respectively, led to the highest growth of the melon, while maximum production was obtained with the use of 112.50 and 165 kg ha-1 of N and K, respectively. The efficiency of N and K use decreased with increasing levels.

As características fitotécnicas, de rendimento e de eficiência de uso dos fertilizantes são relevantes para o manejo racional da fertirrigação, especialmente em cultivo de elevado nível tecnológico. Níveis crescentes de N e K promoverão maior crescimento e produtividade do meloeiro. Neste sentido, objetivou-se avaliar a influência e a eficiência da aplicação de nitrogênio e potássio sobre as características fitotécnicas, de rendimento e de eficiência do meloeiro amarelo em sistema de fertirrigação. O experimento foi conduzido na cidade de Bom Jesus ­ PI, Brasil durante o período de janeiro a abril de 2016. O delineamento experimental adotado foi de blocos em faixas com quatro repetições, e os tratamentos constituídos por cinco níveis de nitrogênio (0, 45, 90, 135 e 180 kg ha-1 na forma de ureia) e cinco níveis de potássio (0, 60, 120, 180 e 240 kg ha-1na forma de cloreto de potássio) aplicados via fertirrigação. Avaliou-se os caracteres fitotécnicos, rendimento de frutos e as eficiências de uso do nitrogênio e do potássio. As aplicações de 180 kg ha-1 de N e 240 kg ha-1 de K promoveram maior crescimento do meloeiro, enquanto que a máxima produção foi obtida com o uso de 112,50 e 165 kg ha-1 de nitrogênio e potássio, respectivamente. As eficiências de uso do nitrogênio e do potássio diminuíram com o aumento dos níveis aplicadas.

Salt stress on physiology, biometry and fruit quality of grafted Passiflora edulis / Estresse salino na fisiologia, biometria e qualidade dos frutos de Passiflora edulis enxertada

The production of grafted passion fruit is an alternative for plant adaptation to saline environments. The objective of this study was to evaluate the effect of salt stress on physiology, biometry and fruit quality of P. edulis grafted on Passiflora spp. The experiment was conducted in completely randomized design, in a 3 x 2 factorial scheme, corresponding to three species of Passiflora (P. edulis, P. gibertii and P. cincinnata) with P. edulis scion and two levels of irrigation water salinity (0.5 - control and 4.5 dS m-1), with four repetitions. Water salinity compromises gas exchanges (CO2 assimilation raste and transpiration) and physiological variables (total chlorophyll and total water consumption) in grafted P. edulis. The interaction between the factors (water salinity x species) compromised only the growth in plant height and number of leaves. In relation to the species, auto-grafted P. edulis stood out from the other species, with higher internal CO2 concentration, number of leaves, stem dry mass, peel thickness, total soluble solids (TSS) of the pulp and TSS/TA ratio (titratable acidity). Auto-grafted P. edulis under saline conditions develops vital mechanisms (TSS and TSS/TA), which attenuates the effects of salt stress on the physico-chemical quality of the fruits.

A produção de maracujazeiro enxertado é uma alternativa para adaptação das plantas a ambientes salinos. Objetivou-se avaliar o efeito do estresse salino na fisiologia, biometria e qualidade de frutos de P. edulis enxertado em espécies de Passiflora spp. O delineamento utilizado foi inteiramente casualizado, em esquema fatorial 3 x 2, sendo três espécies de Passiflora (P. edulis, P. gibertii e P. cincinnata) tendo como copa P. edulis e dois níveis de salinidade de água de irrigação (0,5 ­ testemunha e 4,5 dS m-1), com quatro repetições. A salinidade da água compromete as trocas gasosas (taxa de assimilação de CO2 e transpiração) e variáveis fisiológicas (clorofila total e consumo hídrico total) em P. edulis enxertado. A interação entre os fatores (salinidade da água x espécie) compromete apenas o crescimento em altura de plantas e número de folhas. Em relação às espécies, o P. edulis auto enxertado se destaca em relação as demais espécies apresentando maior concentração interna de CO2, número de folhas, massa seca de caule, espessura da casca do fruto, sólidos solúveis totais (SST) da polpa e razão sólidos solúveis totais por acidez titulável (SST/AT). O P. edulis auto enxertado sob condições de salinidade, desenvolve mecanismos vitais (SST e SST/AT), que atenuam os efeitos do estresse salino na qualidade físico-química dos frutos.

Soil macrofauna associated with cover crops in an Oxisol from the southwest of Piauí state, Brazil / Macrofauna edáfica associada a plantas de cobertura em um Latossolo Amarelo do sudoeste do estado do Piauí, Brasil

The soil macrofauna is fundamental for the maintenance of soil quality. The aim of this study was to characterize the soil macrofauna under different species of cover crops, including monoculture or intercropping associated to two types of soil management in the southwest region of Piauí state. The study was carried out in an Oxisol (Latossolo Amarelo, according to Brazilian Soil Classification System) in the municipality of Bom Jesus, Piauí, distributed in 30 m2 plots. Testing and evaluation of the soil macrofauna were conducted in a 9 × 2 strip factorial design, with combinations between cover crops/consortia and soil management (with or without tillage), with four replications. Soil monoliths (0.25 × 0.25 m) were randomly sampled in each plot for macrofauna at 0‒0.1, 0.1‒0.2, and 0.2‒0.3 m depth, including surface litter. After identification and counting of soil organims, the relative density of each taxon in each depth was determined. The total abundance of soil macrofauna quantified under cover crops in the conventional and no-tillage system was 2,408 ind. m-2, distributed in 6 classes, 16 orders, and 31 families. The results of multivariate analysis show that grass species in sole cropping systems and no-tillage presents higher macrofauna density, in particular the taxonomic group Isoptera. No-tillage also provided higher richness of families, where Coleoptera adult were the second more abundant group in no-tillage and Hemiptera in conventional tillage.(AU)

Os organismos da macrofauna edáfica são fundamentais para a manutenção da qualidade do solo. O objetivo deste trabalho foi caracterizar a macrofauna edáfica sob diferentes espécies de plantas de cobertura, incluindo monocultura ou cultivo consorciado associados a dois tipos de manejo do solo no sudoeste do Piauí. O estudo foi realizado em Latossolo Amarelo (Sistema Brasileiro de Classificação de Solos) no município de Bom Jesus, Piauí, distribuídos em parcelas de 30 m2. O experimento e avaliação da macrofauna edáfica foram conduzidos em um ensaio fatorial em faixas 9 × 2, com combinações entre culturas /consórcios de cobertura e manejo do solo (com ou sem preparo), com quatro repetições. Os monólitos de solo (0,25 × 0,25 m) foram retirados aleatoriamente de cada parcela, para contagem da macrofauna, nas camadas de 0‒0,1, 0,1‒0,2, e 0,2-0,3 m de profundidade, inclusive liteira de superfície. Após a identificação e contagem dos organismos, foi determinada a densidade relativa de cada táxon em cada profundidade. A abundância total da macrofauna edáfica quantificada no experimento foi de 2.408 ind.m-2, distribuídos em 6 classes, 16 ordens e 31 famílias. Os resultados da análise multivariada revelaram que espécies de gramíneas em sistemas de cultivo solteiro e plantio direto favoreceram maior densidade da macrofauna, em especial do grupo taxonômico Isoptera. A ausência de preparo também proporcionou maior riqueza de famílias, destacando-se o grupo taxonômico Coleoptera adulto em plantio direto e Hemiptera em plantio convencional.(AU)