The effect of irrigation strategies and nitrogen fertilizer rates on maize growth and grain yield

In North Florida, increasing nitrogen loads and water quality declines have become a major concern, in part as result of anthropogenic non-point source activities such as agriculture. The main objective of this study was to investigate the effect of irrigation strategies and nitrogen (N) fertility rates on maize biomass, yield and water productivity in sandy soils. The field experiment was conducted 2015-2017 in Live Oak, Florida using a randomized complete block with a split plot design and four replicates. Treatments evaluated five irrigation strategies: (i) GROW, mimicking grower irrigation practices in the region, (ii) SWB, using a soil water balance to schedule irrigation; (iii) SMS, using soil moisture sensors to schedule irrigation; (iv) RED, applying 60% of the GROW treatment; and (v) NON, non-irrigated, and three N fertility rates: (i) low (157 kg N/ha), (ii) medium (247 kg N/ha), and (iii) high (336 kg N/ha). In comparison to GROW, the SWB, SMS and RED irrigation treatments showed no differences in final biomass, N uptake nor grain yield; however, these treatments achieved on average 41, 47, and 36% irrigation reduction, respectively, without impacts on yield during the three maize seasons evaluated. For most of the variables, statistical differences were found between the low and the high N rates, but no differences compared to the medium N rate. A 26% reduction of N fertilizer was achieved using the medium N rate without negative impact on N uptake, biomass nor yield in comparison to the high N fertilization rate. During this experiment, maize N uptake reached a plateau; thus, potential N losses resulted from applications exceeding recommended rates. Furthermore, the implementation of these more efficient irrigation and N fertilizer management strategies reduced irrigation and N fertilizer applications without negative impacts in yield. Thus, these practices may prevent potential N leaching to waterbodies while improving profits.