Abstract
In the last 15 years, there has been an expansion of the use of center-pivots for irrigation in Uruguay. This equipment allows the application of diluted fertilizer in the irrigation water. The study aimed to generate information on fertilization strategies with nitrogen (N) in irrigated maize crops. A study was performed where five treatments were evaluated: T0, without additional nitrogen fertilization to the basal sowing fertilization; C0, cover fertilization with 150 Kg N ha-1 split in three (V3) and seven leaves (V7); F1, idem “C0” but with liquid fertilizer in water; F2, 150 Kg N ha-1 as liquid fertilizer in water split weekly from V3 to reproductive stage (R1); F3, idem "F2" but with 225 Kg N ha-1. Irrigation was done according to water balance and the soil moisture was measured with an FDR probe. The N plant level and biomass were evaluated in states V3, V6, R1 and physiological maturity (R6). The grain yield was determined at harvest. The correlation between the color values and Color Index (InCol) was analyzed in R1 using aerial photography and software, with: % N; biomass; Nitrogen Sufficiency Index (NSI); and grain yield (kg ha-1). The yield was higher in the treatment with the highest N dose, with no significant differences. No differences were found between the sources of N (sulfur urea and Fertec®) for the evaluated variables. A high correlation was obtained between the colors and the InCol and the cultivation variables.
Highlights
Maize (Zea mays L.) is the cereal with the highest annual production in the world
3.1 Analysis of soil and concentrated solution for fertilization According to the results of the measurements of the soil textural analysis (Table 1), the corresponding classification made from Altamirano and others(13) is reaffirmed
The A horizon had an apparent density value of 1.53 g cm-3, high compared to its silty clay loam granulometry, which could indicate the existence of a compaction effect, which could occur in the B and C horizons(35)
Summary
Maize (Zea mays L.) is the cereal with the highest annual production in the world. The production area is widespread and encompasses various environments(1). In Uruguay, maize crops cover approximately 80,000 hectares each year, with average yields of 4.9 Mg ha-1 that exceptionally exceed 6.0 Mg ha-1(2). In the 2015-2016 harvest, the crop presented an average yield under irrigation of 8.5 Mg ha-1, 46% more than the rainfed yield. The main limitation of summer crop yield in Uruguay is water availability. There is high interannual rainfall variability, generally the water deficit coincides with the critical period of the crops, due to the higher evapotranspiration values of the year and the low storage capacity of available water in the soil(5)(6)(7). For approximately 15 years there has been an expansion of extensively irrigated crops, coinciding with the number of imported center pivots, which were 51 in 2000 and 422 in 2015(8)
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