Response of soil fungi and biological processes to crop residues in no-tillage system

Abstract

Soil management and crop rotation can directly affect the soil microbial community. This study aimed at determining soil quality indicators and soilborne fungi in a no-tillage system. A randomized blocks design, in a 3 × 2 factorial arrangement, was used. Three cover crops (palisade grass, millet and common bean) provided straw and root residues to the following crops of corn and soybean. The common bean-soybean sequence provided little soil covering and higher metabolic quotient and soil basal respiration and total enzymatic activity, as well as a general increase of soilborne fungi. The principal component analysis revealed that 76.61 % of the variance can be explained by the three first components, with cover crops, soil basal respiration and metabolic quotient regarded as the main qualitative and quantitative sources of variance in the first component. Carbon from the microbial biomass was the soil quality indicator best correlated to crop yield and negatively correlated to Fusarium solani density. The Rhizoctonia solani population was correlated with higher metabolic quotient and soil total enzymatic activity and basal respiration. The palisade grass crop favored soil fungistasis and enhancement of antagonist Trichoderma spp. populations. The multivariate approach demonstrated the association of soil fungi with soil quality indicators, as well as a higher influence of cover crops on the variance observed, in comparison to cash crops.

Nitrogen Accumulation and Export by Common Bean as a Function of Straw and N Splitting in No-Tillage System

“…Soratto et al (2013b), studying early N application for the sowing of common bean, also found that its yield was little influenced by the previous cropping system (maize and maize intercropped with U. ruziziensis grass). In addition, it should be considered that agricultural systems are complex, which requires a holistic view of the processes and impacts of these agroecosystems (PANKHURST et al, 1995, OLIVEIRA et al, 2016. However, in the splitting schemes 30-60-00, 30-00-60, 00-60-30 and 00-45-45, this attribute was superior when the common bean was cultivated in succession to maize as single crop and intercropped with U. ruziziensis grass.…”

“…In addition, studies suggest the effect of exudates of the roots of this forage on N cycling, suppressing the processes of nitrification and leaching (GOPALAKRISHNAN et al, 2009). N is the most required nutrient by common bean, which needs 30 to 45 kg of N for every 1,000 kg of grains (OLIVEIRA;THUNG, 1988). Due to the shallow root system and short cycle, the requirement for readily available N during the initial stages is higher for this crop.…”