Decomposição da fitomassa de plantas de cobertura e liberação de nitrogênio em função da quantidade de resíduos aportada ao solo sob sistema plantio direto

Abstract

Decomposição da fi tomassa de plantas de cobertura e liberação de nitrogênio em função da quantidade de resíduos... Ciência Rural, v.44, n.5, mai, 2014. 801Decomposição da fi tomassa de plantas de cobertura e liberação de nitrogênio em função da quantidade de resíduos aportada ao solo sob sistema plantio direto Fitomass decomposition and nitrogen release of cover crops in function of the level of residue input to soil under no-tillage system ABSTRACT The no-tillage system success relies on higher addition of different types of crop residues to the soil, each one with specifi c decomposition kinetics which drives the net mineralization and immobilization of the nitrogen (N) in the soil. This manuscript had as objective to evaluate the decomposition rate and N released from winter cover crops residues under different above ground biomass input to the soil. The experiment was carried out in the experimental area of the Soil Department at Federal University of Santa Maria, in random complete block design, with three replications, during 2003/04 and 2004/05. The decomposition and the N released from black oat, oil radish and hairy vetch residues were investigated using mesh bags of decomposition containing fi tomass equivalent to 3, 6 and 9 Mg of dry matter ha -1 placed in plots with 80 m 2 with the same level of crop residues used in the mesh bags. They were collected at 7, 14, 28, 42, 63, 84, 113 and 141 days after cover crops management. The amount of residues input did not infl uence the decomposition rate. However, the N mineralization and immobilization processes were affected by the level of residues input and they were driven by C/N ratio. The larger decomposition residues rate and higher N release followed the order: vetch, radish oil and black oat. The C/N ratio drives the size of labil and recalcitrant compartiments of cover crops fi tomass.

Do cover crops improve the productivity and industrial quality of upland rice?

“…According to Aita, Giacomini, and Ceretta (2014), crop residues with a high C/N ratio are decomposed more slowly. Acosta, Amado, Silva, Santi, and Weber (2014), studying cover crops decomposition, concluded that the decomposition process is regulated by the C/N ratio of the straw.…”

Decomposition and release of nutrients from crop residues on soybean-maize cropping systems

“…Straw is an important nutrient reservoir, which can be gradually, quickly, or even intensely made available (Rosolem et al, 2003). This leach is influenced by the activity of microorganisms found in the soil, by their quality (carbon/nitrogen (C/N) ratio) and amount, by the weather conditions -with emphasis on temperature and rainfall -and by the contact of straw with soil (Acosta et al, 2014). Nutrients leached by the straw, mainly potassium (K) -which presents short half-time life -are important to nurture the subsequent culture.…”

Technical and economic feasibility of irrigated wheat as a function of nitrogen doses, sources, and inoculation with Azospirillum brasilense

“…The grain yield in 2015 adjusted to the quadratic function for doses in the treatments with and without inoculation with A. brasilense, with a positive response up to 142 and 134 kg ha -1 of N, respectively. The N doses mentioned above to obtain the maximum yield of grains were high, because the wheat was cultivated on the maize stover, that is, part of the N that was applied could have been used by immobilized decomposers and/ or mineralizing soil microorganisms (ACOSTA et al, 2014), since the higher the C/N ratio of the stover, the longer the N release time of the vegetal residue, and consequently N demand will be higher for the mineral fertilizer. Means followed by the same letters, in the column, do not differ among themselves by the Tukey's test at 5% probability.…”