ABSTRACT There is a need for greater knowledge about the medium- and long-term effects of prescribed fire management on soil in ecosystems prone to wildfires and more vulnerable to climate change. This study examined the short- and medium-term effects of prescribed fire on soil chemical properties and chemical fractions of soil organic matter (SOM) in two positions of the landscape in a high-elevation grassland environment. The ecosystem is located in the mountain peaks of southeastern Brazil associated with the Atlantic Forest biome. Prescribed fire was conducted in 2017 to reduce understory vegetation and thus prevent potential severe wildfires. Soil samples were collected at the layers of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m, at eight composite sampling. The composite samples were collected on five different occasions: before the prescribed fire, and 10, 30, 90, and 240 days after the prescribed fire. Soil chemical properties, total organic carbon, labile C, and chemical fractionation of SOM were analyzed. All soil properties investigated were affected by the prescribed fire, with variations in landscape position, duration of effect, and soil layer. In the backslope area, the medium-term effect of fire was negative and induced soil degradation and induced soil degradation. In the footslope area, the system showed greater resilience to the effects of fire, as indicated by the recovery of the soil’s chemical properties. These results can help assess the suitability of controlled burning of vegetation for managing risks of fire in mountainous regions, such as high-elevation grasslands.

ABSTRACT The recent approach of eliminating the use of fire for sugarcane harvesting (green cane) resulted in managing the crop on a trash-blanketed soil, which changed the content and dynamic of carbon and the nitrogen requirement. These alterations are relevant due to economic and environmental aspects of sugarcane production systems. This study aimed to evaluate changes in total organic carbon (TOC), total nitrogen (TN) and soil organic matter fractions with the application of N-fertilizer on the residues of green cane. The experiment was with sugarcane at the fourth ratoon in Linhares, Espírito Santo State, Brazil. The soil is a Xanthic Dystrudults, originated from Barreiras Group sediments in the coastal tableland region. The treatments were set in a completely randomized blocks experimental design and consisted of N (as ammonium sulphate) dosages varying from 80 to 160 kg N.ha–1 and the control. The application of increasing N doses resulted in accumulation of TOC and carbon in the humic, granulometric and oxidizable fractions of soil organic matter (SOM). It was obtained a model adjustment for quadratic regression for TOC, NT and SOM fractions. The doses between 80 and 100 kg N.ha–1 were the most favorable to accumulate carbon and the SOM fractions. N doses higher than 100 kg N.ha–1 favored SOM mineralization. The SOM fractions were responsive to application of N-fertilizer on harvesting residues of the green cane management area.

ABSTRACT The recent approach of eliminating the usage of fire for sugarcane harvesting resulted in managing the crop on a trashblanketed soil, to which a proper recommendation of N fertilization is lacking, a problem that remains in the coastal tablelands of the Espírito Santo State, Brazil. This study aimed at evaluating the effect of increasing N rates on stalk and sugar yields and the N use efficiency by the crop. The experimental area planted with sugarcane, at the first ratoon, is located in Linhares, Espírito Santo State. The treatments consisted of N rates varying from 80 to 160 kg N∙ha−1 as ammonium sulphate, and a control without N, in a completely randomized blocks experimental design. Stalk yield increased with the N rate, and fitting the results to a quadratic function suggests no response to fertilizer rates above 130 kg N∙ha−1. The highest margin of agricultural contribution was obtained at the rate of 100 kg N∙ha−1. The N use efficiency decreased from almost 49 to 38%, when the N rate increased from 100 to 160 kg N∙ha−1. There was no effect of increasing N rates on the sugar concentration, although the sugar yield response was positive and strongly influenced by the stalk production. Results showed the importance of reassessing the adequate N rate for maximizing yield in green cane production systems.

Este trabalho foi realizado com o objetivo de avaliar o consumo, a digestibilidade aparente dos nutrientes e o balanço hídrico em equinos consumindo feno de capim coast-cross em diferentes formas físicas. Foram utilizados quatro equinos mestiços, com idade de 30 meses e peso vivo médio de 200 kg. Os animais foram alimentados com feno de capim coast-cross em quatro formas físicas: inteiro; picado (5 cm); moído a 5 mm; ou moído a 3 mm. O delineamento experimental utilizado foi em quadrado latino 4 × 4, com 10 dias de adaptação às dietas em cada período experimental, 4 dias de coleta de fezes e 1 dia de coleta de urina.A estimativa da digestibilidade aparente dos nutrientes das dietas foi realizada pelo método de coleta total das fezes e a urina foi coletada durante 24 horas utilizando-se coletores de urina. Os coeficientes de digestibilidade aparente e o consumo de nutrientes não diferiram com o processamento do feno, no entanto, o tempo de consumo reduziu com a moagem do feno.Houve maior retenção de água, estimada pelo balanço hídrico, quando fornecido feno picado ou moído a 3 mm. O consumo e a digestão dos nutrientes não são influenciados pelo nível de moagem do feno, porém o balanço hídrico é afetado pelas formas físicas do feno. Não há relação direta entre a redução do tamanho da partícula do feno e o aumento da retenção de água.

This study was carried out to evaluate intake, apparent nutrient digestibility and water balance in horses fed on different forms of coast-cross hay. Four crossbreed horses, 30 months of age and 200 kg body weight were used. Horses were fed coast-cross hay in four physical forms: long hay; chopped hay (5 cm); ground hay (5 mm) and ground hay (3 mm). The experiment was performed in a 4 × 4 Latin Square design with 15 days for each experimental period (10 days for adaptation to the diets, four days for feces collection and one day for urine collection). Apparent nutrient digestibility was estimated by total feces collection and urinary collection was carried during 24 hours by urine collectors. Apparent digestibility coefficients and nutrient intake did not differ among the diets but the intake time was reduced with hay processing. There was greater water retention, estimated by water balance, when chopped hay or ground hay (3 mm) were fed. Intake and nutrient digestibility were not influenced by levels of hay grinding, but water balance was influenced by the different forms of hay, but a direct relationship was not observed between fiber length reduction and increased water retention.