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Nitrogen variable rate fertilization in corn crop prescribed by optical sensor

2020; Taylor & Francis; Volume: 43; Issue: 11 Linguagem: Inglês

10.1080/01904167.2020.1729805

1532-4087

Rodrigo Nogueira Martins, Francisco de Assis de Carvalho Pinto, Altair Dias de Moura, Wagner da Cunha Siqueira, Flora Maria de Melo Villar,

Plant nutrient uptake and metabolism

Nitrogen (N) plays a key role in the optimization between corn grain yield and its economic return. Based on that, this study aimed to evaluate the technical feasibility of a portable chlorophyll meter for recommending an economic dose of N under variable rate using different threshold values of the nitrogen sufficiency index (NSI). The study was conducted in Januária-MG (15° 28′ 55″ S, 44° 22′ 41″ W; 474 m) from February to June 2018. The experimental design was a randomized block with 5 treatments and 5 replicates, which were: T0: without N application; T1: 112 kg ha−1 of N (pre-fixed doses), with 50% (56.00 kg) applied in the four expanded leaves stage (V4) and 50% in the V8 stage; T2: 44.8 kg ha−1 of N in V4 + 22.4 kg ha−1 of N through variable rate based on NSI (< 95%) in the stages V8, V10 and V14; T3: 44.8 kg ha−1 of N in V4 + 22.4 kg ha−1 of N through variable rate based on NSI (< 98, 95 and 93%) in the same stages; and T4: 33.6 kg ha−1 of N in V4 + 33.6, 28.0 and 16.8 kg ha−1 of N according to NSI (< 98, 95 e 93%) in V8, V10 and V14, respectively. Variable rate treatments were more efficient than the pre-fixed dose, as they consumed less N and resulted in the same grain yield. Furthermore, the NSI threshold of 95% resulted in higher N use efficiency in the evaluated stages.