Diagnosis and export of macronutrients in maize for silage under doses of nitrogen via fertigation

Abstract

Maize is prominent in silage production; however, the cropping season may compromise its yield performance. Nevertheless, nitrogen fertilization via irrigation has the potential to ensure high yield. The objective was to evaluate the levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in the diagnostic leaf and their exports in maize for silage cultivated under increasing doses of N via fertigation, in Canindé de São Francisco, Sergipe, Brazil. The experiment was conducted in summer (January to April) and winter (June to September) of 2016. The experimental design was a randomized complete block design, with four replications and four N doses (0, 80, 160, and 240 kg ha⁻¹), with a combined analysis of the growing seasons. Nutrient contents in the diagnostic leaf were increased with increasing N doses, except for Ca. Maize cultivated in winter showed higher contents of N (28.65 g kg⁻¹) and P (3.59 g kg⁻¹), while in summer the plants showed higher values for K (25.2 g kg⁻¹), Ca (4.60 g kg⁻¹), and Mg (8.52 g kg⁻¹). The decreasing order of nutrient export was: N > K > Mg > Ca > P. In summer, exports of P               (64.34 kg ha⁻¹), K (156.99 kg ha⁻¹), and Mg (78.35 kg ha⁻¹) were favored up to the N dose of 124.43 kg ha⁻¹. In the winter season, there were higher exports of N (185.01 kg ha⁻¹), Mg (78.83 kg ha⁻¹), and Ca (74.43 kg ha⁻¹), especially with the application of 240 kg ha⁻¹ of N.