Plant sensors for nitrogen monitoring and fertilization impacts on the nutrient dynamic on maize crop

Abstract

Nitrogen (N) is the micronutrient most demanded in agriculture, of which deficiency strongly limits crop production. This study was comprised of two experiments conducted under irrigation, in Red Latosol areas, of Embrapa Milho e Sorgo, in Sete Lagoas, MG, Braz il. The first experiment regarded the effectiveness of nitrogen monitoring sensors and the productive potential of the corn. The second experiment focused on the effects of doses of nitrogen for corn coverage over the dynamics of ammonium and nitrate in the soil, losses by nitrous oxide emission and by ammonium and nitrate leaching, nutrient use by the plant, productivity response and N balance in the crop in question. In experiment 1, spectral readings were performed with N sensors and plants were collected along the cycle of four corn hybrids, cultivated in medium and high fertilization levels. In addition to being influenced by the fertilization levels, the sensor reading values varied according to the corn hybrids, phenological stages and their interaction. The sensors showed low prediction capacity of the nutritional status of nitrogen of the corn in the studied environments. For a greater sensitivity for detecting differences in the growth and biomass accumulation intensities, the GreenSeeker is the most effective for predicting corn productive potential. In experiment 2, a corn hybrid was cultivated in area with drainage lysimeter, receiving treatments with 60, 150 and 396 kg ha -1 of N coverage. Static chambers were used for collecting nitrous oxide emissions after coverage fertilization. Along the cycle, soil samples were collected at 60 cm pf depth for quantifying ammonium and nitrate stocks, while leaching was determined in soil solution samples percolated in the lysimeters. Plant samples were collected in many phenological stages to evaluate N absorption and accumulation in the corn dry mass, and productivity at the end of the cycle. From the measures variables, the balance of N credits and losses were estimated for the crop. The doses of nitrogen coverage resulted in no significant differences in plant accumulation and grain productivity. The losses of N from the system were higher with the increase in the doses of the nutrient coverage, but the differences were disproportionate to the variation if quantity provided. In the estimate of N balance with the lower coverage dose, 40% of the nutrient credits in the system were exported in the harvested grains, 6% correspond to losses by volatilization and leaching, 49% remained as residual stock and 0.2% were non-detected N. Nitrogen surplus must be avoided during fertilization of environments with excessive potential of availability from previous crops, given that the system presents limited capacity for nutrient storage, predisposing losses that reduce the efficiency of fertilization and can lead to economic and environmental losses.