Abstract
ABSTRACT The objective of this work was to evaluate the effects of the application of phosphogypsum and vinasse on soil chemical properties and productivity and nutritional characteristics of alfalfa (Medicago sativa). The experiment was conducted in a randomized block design, using a 3×5 factorial arrangement, with three vinasse rates (0, 150 and 300 m3 ha-1) and five phosphogypsum rates (0, 3, 6, 9 and 12 Mg ha-1). The alfalfa chemical composition and shoot dry matter (SDW) and soil chemical properties (in the layers 0.0-0.2 and 0.21-0.4 m) were evaluated. The vinasse rates increased the soil potassium contents, while the phosphogypsum rates promoted linear increases in soil calcium and sulfur contents. The base saturation was increased and the magnesium content showed a quadratic response on the layer 0.21-0.4 m with the increase in phosphogypsum rates. The calcium, magnesium and phosphorus contents in the alfalfa leaves were lower with vinasse application. The phosphogypsum rates promoted linear increases in alfalfa SDW. Vinasse rated 150 m3 ha-1 was been enough to SDW increase. Calcium and magnesium contents in the leaves fitted a quadratic model, with maximum calcium content in the phosphogypsum rate of 9.5 Mg ha-1 and the minimum magnesium content in the phosphogypsum rate of 8.7 Mg ha-1. The leaf sulfur contents in all vinasse rates and leaf potassium contents in the highest vinasse rate showed maximum accumulation at near 9 Mg ha-1 of phosphogypsum.
Highlights
The Brazilian sugarcane production has been standing out, mainly due to its high yields and high energy efficiency, achieved especially on the ethanol processing
The experiment was conducted in a randomized block design, using a 3×5 factorial arrangement, consisting of three vinasse rates (0, 150 and 300 m3 ha-1) and five phosphogypsum rates (0, 3, 6, 9 and 12 Mg ha-1), with three replications
Increases in leaf S are usually directly related to the nutrient supply due to phosphogypsum application (RAIJ, 2011), as observed in this study
Summary
The Brazilian sugarcane production has been standing out, mainly due to its high yields and high energy efficiency, achieved especially on the ethanol processing. Vinasse improves soil fertility, supplying nutrients such as potassium (K+), calcium (Ca2+) and magnesium (Mg2+) and organic matter (OM), which have average concentrations of 4.92, 2.08, 0.49 and 2.70 g L-1 in the vinasse, respectively (LEITE, 1999). The application of vinasse has increased sugarcane production (SILVA; BONO; PEREIRA, 2014). Basso et al (2013) used vinasse for 100% of potassium fertilization, applying 200 m3 ha-1 of vinasse and found an increase of almost 10% in K+ content in the topsoil, and increases of 7 to 15 Mg ha-1 in sugarcane yield. Other studies reported increases in K+, Ca2+, Mg2+ and S-SO42contents due to vinasse application (CARVALHO et al, 2013; SILVA; BONO; PEREIRA, 2014; PAULA; CARVALHO; NOGUEIRA, 1992; ANDREOTTI et al 2015)
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