Abstract
ABSTRACT Early potassium fertilization in previous crops may be beneficial to the main crop in succession. The objective of this study was to investigate the behavior of the soybean crop as a function of potassium (K) doses in the previous crops, associated or not with K application in soybean. The experiment was carried out from 2012 to 2015 in an experimental area of the Faculty of Engineering, UNESP, Campus of Ilha Solteira-SP, located in Selvíria-MS, Brazil. For the previous crops, a randomized block design was used in a 3 x 4 factorial scheme with four replications, i.e., three previous crops (maize, sorghum and millet) and four K doses (0, 35, 70 and 120 kg ha-1 of K2O). For soybean in succession, a randomized complete block design was used in the split-plot scheme. The treatments were arranged in a 3 x 4 x 2 factorial scheme with four replicates, i.e., soybean sowing on three types of straw (maize, sorghum and millet), residual of the four K doses and with or without top-dressing K fertilization in the soybean. Millet accumulated higher K content in comparison to maize and sorghum. The return of K to the system by millet is similar to that by maize. Potassium doses in the previous crops do not alter their dry matter production and K content. Potassium fertilization in the soybean crop in succession to millet allows higher yields.
Highlights
Most of the Brazilian territory exploited with soybean cultivation is in areas with high degree of weathering, highlighting an important program of potassium fertilization (Assis et al, 2013)
The present study aimed to evaluate the productive behavior of soybean as a function of K doses applied in the previous crops, associated or not with top-dressing K fertilization in soybean
The residual effect of K doses applied in the previous crops on the soybean in succession becomes evident, which may be a possibility of period to apply this nutrient
Summary
Most of the Brazilian territory exploited with soybean cultivation is in areas with high degree of weathering, highlighting an important program of potassium fertilization (Assis et al, 2013). Along with nitrogen (N), potassium (K) is the second nutrient most required by the soybean crop along its cycle; N can be supplied by biological fixation, whereas K needs to be applied in the soil via fertilizers, because Brazilian soils have low contents of this element (Silva & Lazarini, 2014). K in plant residues is not incorporated to the carbon chains and, after plant harvest or senescence, it rapidly returns to the soil in the form readily available to the crops (Rosolem et al, 2007). At high doses, fertilization must be split, especially in sandy soils (Foloni & Rosolem et al, 2008)
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