Abstract
ABSTRACT The efficiency of nitrogen fertilizer in corn is usually low, negatively affecting plant nutrition, the economic return, and the environment. In this context, a variable rate of nitrogen, prescribed by crop sensors, has been proposed as an alternative to the uniform rate of nitrogen traditionally used by farmers. This study tested the hypothesis that variable rate of nitrogen, prescribed by optical sensor, increases the nitrogen use efficiency and grain yield as compared to uniform rate of nitrogen. The following treatments were evaluated: 0; 70; 140; and 210 kg ha-1 under uniform rate of nitrogen, and 140 kg ha -1 under variable rate of nitrogen. The nitrogen source was urea applied on the soil surface using a distributor equipped with the crop sensor. In this study, the grain yield ranged from 10.2 to 15.5 Mg ha-1, with linear response to nitrogen rates. The variable rate of nitrogen increased by 11.8 and 32.6% the nitrogen uptake and nitrogen use efficiency, respectively, compared to the uniform rate of nitrogen. However, no significant increase in grain yield was observed, indicating that the major benefit of the variable rate of nitrogen was reducing the risk of environmental impact of fertilizer.
Highlights
Corn (Zea mays L.) is the main cereal grown in Brazil, with an area over 15 million ha
The plant attributes related to N nutritional status of corn, assessed at VT, were directly related to the rate of N fertilizer, providing the increased N content, N uptake, the SPAD Index, vegetation index (VI) determined by the optical sensor, and corn grain yield, as expected
The treatment with the highest N rate (210URN) increased by 56% the plant N uptake and by 50% the plant N content, which is important for cell division and expansion, besides being the main component for the chlorophyll molecules responsible for photosynthesis, driving the plant accumulation of carbohydrates and plant growth (Malavolta, 1997; Lobell, 2007)
Summary
Corn (Zea mays L.) is the main cereal grown in Brazil, with an area over 15 million ha. The variable rate of N (VRN) adjusts the fertilizer input according to the plant nutritional status In this case, one most frequently used fertilizer prescription is increasing the N rate in plants with low nutritional status, where there is a higher probability of response to the input. One most frequently used fertilizer prescription is increasing the N rate in plants with low nutritional status, where there is a higher probability of response to the input This strategy commonly results in NUE optimization (Raun et al, 2005; Singh et al, 2006, Bragagnolo et al, 2013b). The specific objectives were: a) to evaluate the efficiency of the sensor to capture the corn nutritional status in different growth stages; and b) to compare NUE and corn grain yield under VRN and URN fertilization strategies
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