Physical attributes and organic material in pastures of Brachiaria brizantha at degradation levels

Pastures cover, in Brazil, around 165 million ha, most of them are at some degradation level. Recovering these pastures is essential. The objective of this study was to evaluate the sensibility of soil organic matter (SOM) and its physical attributes in pasture soil at different degradation levels (1 to 4), Capoeiras (1 and 2) and secondary Forest (Control). Samples were collected at four depths (0.00-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m). We verified higher values for SOM and hydraulic conductivity (Ko) in Forest, especially in the most superficial layer (0.00-0.05). We noted low values for macroporosity in this area. In all areas under Pastures lower values for Ko were observed in the superficial layer (0.00-0.05 m) when compared to layers 0.05-0.10 and 0.10-0.20 m, which indicates that the pasture management and cattle trampling negatively affect the physical quality of the pastures. For field capacity and wilting point the average values were observed in Pasture 4 (more degraded), which caused higher values for water availability. According to the principal components analysis, except for SOM at 0.20-0.40 m, all variables studied presented correlation above 0.6. From grouping analysis, we separated 3 groups: Forest; Capoeiras 1 and Capoeira 2 and Pastures 1 to 4.

Can short-term pasture management increase C balance in the Atlantic Rainforest?

Few studies have shown the importance of different pasture management practices on C storage and the reduction of CO2-C emissions in tropical conditions. The objective of the present study was to determine short-term changes in C pools and C balance from different pasture management practices established in the Atlantic Rainforest. A field study was carried out in Alegre, ES, Brazil from September 2013 to August 2014 to investigate the first-year effect of pasture management practices on a Udult clayey soil. The different pasture management practices studied included the following: control (CON), chiseled (CHI), fertilized (FER), burned (BUR), integrated with crop-livestock (iCL) systems, and plowed and harrowed (PH). Monthly disturbed and undisturbed soil samples were taken at two different layers (0.00-0.05 and 0.05-0.20 m) for chemical, physical, and organic matter characterization. C inputs monitored in aboveground pools included plant aerial parts and litter, and belowground pools included roots and soil C stocks. C outputs monitored were CO2-C emissions, erosion water, and sediment. C balance was considered the difference between inputs and outputs in each treatment during four seasons. The spring and summer seasons had a strong influence on C inputs and outputs where there is significant difference between spring and summer, while the autumn and winter seasons had less influence. All pasture management practices exhibited positive C balance after 1 year. High values of C balance were verified in pastures fertilized (FER) (53.04 Mg ha-1 year-1. Intermediate C balance was found in the burned (BUR) (40.84 Mg ha-1 year-1), traditional control (CON) (40.31 Mg ha-1 year-1), and in the plowing and harrowing (PH) (40.02 Mg ha-1 year-1) management practices. The practices of chiseled (40.00 Mg ha-1 year-1) and integrated crop-livestock systems (iCL) (59.06 Mg ha-1 year-1) resulted in low C balance.

Soil, water, and nutrient losses from management alternatives for degraded pasture in Brazilian Atlantic Rainforest biome.

The objective of this study was to evaluate sediment, water and nutrient losses from different pasture managements in the Atlantic Rainforest biome. A field study was carried out in Alegre Espiríto Santo, Brazil, on a Xanthic Ferralsol cultivated with braquiaria (Brachiaria brizantha). The six pasture managements studied were: control (CON), chisel (CHI), fertilizer (FER), burned (BUR), plowing and harrowing (PH), and integrated crop-livestock (iCL). Runoff and sediment samples were collected and analyzed for calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P) and organic carbon contents. Soil physical attributes and above and below biomass were also evaluated. The results indicated that higher water loss was observed for iCL (129.90mm) and CON (123.25mm) managements, and the sediment losses were higher for CON (10.24tha-1) and BUR (5.20tha-1) managements when compared to the other managements. Majority of the nutrients losses occurred in dissolved fraction (99% of Ca, 99% of Mg, 96% of K, and 65% of P), whereas a significant fraction of organic carbon (80%) loss occurred in a particulate form. Except for P, other nutrients (Ca, Mg and K) and organic carbon losses were higher in coarse sediment compared to fine sediment. The greater losses of sediment, organic carbon, and nutrients were observed for CON followed by BUR management (p<0.05). Our findings indicated that the traditional pasture management adopted in the Atlantic Rainforest needs to be rethought and burned management should be avoided. Based on the water, soil, and nutrient losses from various practices, to reduce pasture degradation, farmers should adopt edaphic practices by applying lime and fertilize to improve pasture growth and soil cover, and reducing soil erosion in the hilly Brazilian Atlantic Rainforest biome.

Escórias de siderurgia na nutrição de gramíneas cultivadas em latossolo vermelho-amarelo / Blast furnace slags in the grass nutrition cultivated in oxisol

As escórias de siderurgia alteram positivamente as características químicas do solo, contribuindo assim para o aumento na disponibilidade de nutrientes para as plantas. O objetivo deste estudo foi avaliar o uso de escórias de siderurgia na nutrição mineral de Brachiaria decumbens e de Brachiaria brizantha cv. Marandu cultivadas em Latossolo Vermelho Amarelo distrófico (LVA). Foram coletadas amostras de LVA em uma área sob pastagem de Urochloa sp. Após a coleta, o solo foi seco ao ar e peneirado em malha de 2 mm, com posterior caracterização química e física. O experimento foi montado num esquema fatorial 2 x 2 x 5 sendo duas espécies de braquiária (B. brizantha e B. decumbens), duas escórias de siderurgia (escória A e escória B) e cinco doses de SiO2 (0, 500, 1000, 1500 e 2000 kg ha-1), em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram incubados por 30 dias. Após este período, espécies de gramíneas B. brizantha e B. decumbens foram transplantadas para as unidades experimentais (vasos de 4 dm3). Após 40 e 80 dias realizou-se o 1º e 2º corte da parte aérea, respectivamente. Foram avaliados os teores de N, P e K da parte aérea das gramíneas e calculadas as quantidades acumuladas desses nutrientes. Os teores e acúmulos dos nutrientes variaram em função da escória, da gramínea e da época do corte. A escória A proporcionou maiores teores de N, P e K na parte aérea de ambas as gramíneas.

The slags positively alter the chemical characteristics of the soil, thus contributing to the increase in the availability of nutrients to plants. The objective of this study was to evaluate the use of blast furnace slags in mineral nutrition of Brachiaria decumbens and of Brachiaria brizantha cv. Marandu cultivated in Oxisol. Samples were collected from dystrophic Oxisol from a pasture area of Brachiaria sp. After the samples were collected, the soil material was air dried and sieved through a 2 mm sieve for chemical and physical characterization. The experiment was held in a completely randomized design with four replications in a factorial scheme of 2 x 2 x 5 with two species of Brachiaria (B. brizantha and B. decumbens), two blast furnace slags (slag A and slag B) and five doses of SiO2 (0, 500, 1000, 1500 and 2000 kg ha-1). The treatments were incubated for 30 days. Upon this period, the grass species of B. brizantha and B. decumbens were sown and transplanted separately to the experimental units. After 40 and 80 days, the first and second cutting of the shoots were held, respectively. The contents of nitrogen, phosphorus, potassium were quantified in the grasses shoots and calculated the amounts of accumulated nutrients. The contents and accumulated nutrients varied due to the slag, grass and cutting of the shoots. Slag A provided higher contents of nitrogen, phosphorous and potassium in the shoots of both type of grasses. The slags are an alternative to increase the quality of grasses of Brachiaria.