Abstract
ABSTRACT Determining nitrogen (N) accumulation and export by common bean as a function of straw and of the splitting of this nutrient is very important, aiming at the management and sustainability of agricultural systems. This study aimed to determine the N accumulation and export by common bean as a function of Zea mays and Urochloa ruziziensis grass straw (maize, maize/U. ruziziensis intercropping and U. ruziziensis) and splitting of top-dressing N fertilization. The experiment was conducted in Jaboticabal-SP-Brazil, during the 2012/13 crop season, in a Red Eutrophic Oxisol (Eutrudox) in no-tillage under irrigation. The experimental design was a randomized block with split plots with four replicates, totaling 120 subplots sized in 25m2 each. The plots consisted of the cropping systems prior to common bean: maize, maize/ U. ruziziensis intercropping and U. ruziziensis. The subplots were composed of ten top-dressing N fertilization splitting schemes (NS) at the phenological stages V3, V4 and R5 in different combinations. Common bean grain yield differs among cropping systems and as a function of top-dressed N split application. U. ruziziensis grass as single crop promotes greater N accumulation in common bean shoots compared to maize and its intercropping with U. ruziziensis grass. Regardless the cropping system, top-dressing N application in a single dose (90 kg ha-1) at V4 leads to similar accumulations and exports to those found in the absence of N fertilization. Splitting schemes with N application at the R5 stage increase the exports of this nutrient by common bean in succession to maize and its intercropping with U. ruziziensis grass.
Highlights
The no-tillage system (NTS) is largely responsible for increasing the sustainability of agriculture in the tropics
The experiment was conducted in the 2012/13 agricultural year at the Farm of Teaching, Research and Extension of the São Paulo State University UNESP/FCAV, Jaboticabal, SP, Brazil (21o 14’ S; 48o 17’ W; average altitude of 586 meters) in soil classified as Latossolo Vermelho eutrófico típico, that is, Red Eutrophic Oxisol (Eutrudox), with gently undulating relief under Cerrado vegetation (SOIL SURVEY STAFF, 2014), of clayey texture, with 533 g kg-1 of clay, 193 g kg-1 of silt and 274 g kg-1 of sand
The shoot dry mass production of common bean was influenced only by the previous cropping systems, with the highest value obtained after the systems with U. ruziziensis grass (Table 1)
Summary
The no-tillage system (NTS) is largely responsible for increasing the sustainability of agriculture in the tropics Practices such as minimal soil disturbance, maintenance of straw, crop rotation and permanence of living roots substantially contribute for the agricultural systems to remain productive for longer periods. The NTS faces difficulties with the formation and maintenance of straw in tropical regions, especially in climates with hot and rainy summer and dry winter (BUTENSCHOEN; SCHEU; EISENHAUER, 2011). Under these conditions, there is a high rate of decomposition of plant residues that, combined with the difficulty for their production in the off-season (autumn and winter), compromises this system. The benefits of U. ruziziensis grass are related to high adaptability to acidic, low-fertility soils, nutrient cycling, better N use, reduction of diseases such as white mold, dry root rot and rot by Fusarium and Rhizoctonia (KLUTHCOUSKI et al, 2013)
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