35-3 Evaluation of Soil Mineral Nitrogen Content in Different Irrigation Systems during Potato Crop Development.
Monday, October 23, 2017: 8:35 AM
Marriott Tampa Waterside, Grand Ballroom D
Sandy soils with shallow water table induce soil nutrients leaching in response to irrigation and rainfall, in particular NO3- and NH4+. The objective of this study was to determine the spatial and temporal distribution of soil N fertilizer applied at different timing and rates strategies in a sandy soil under seepage, tile drainage, subsurface drip (SDI) and sprinkler irrigation. A factorial randomized complete block design with three N-rates (0, 56, 112 kg.ha-1) applied at planting and two N-rates (56 and 112 kg.ha-1) applied at emergence and tuber initiation were setup within each irrigation system in 2015 and 2016 potato seasons. Soil-N content (NO3- and NH4+) was determined at five-potato growth stages for 0-15, 15-30 and 30-60 cm of soil depth. During both potato seasons, the soil water flux influence the soil N distribution. Water table control irrigation systems had higher soil-N content measured at 0-15 cm of soil than deeper soils, while the sprinkler irrigation had higher soil-N at 15-30 cm of soil than other irrigation systems. Regarding growth stages, soil-N was higher at tuber initiation than other growth stages when potato was overhead sprinkler irrigated, but water table control irrigation systems had the highest soil-N at maturity. Overall, N-rates above 56 kg.ha-1 had no significant differences in soil-N with planting application timing. N-rate treatments applied at emergence required 112 kg ha-1 to increase soil mineral N in the 0-15 cm of soil, while 112 kg.ha-1 of N applied at tuber initiation had higher soil-N than 56 kg.ha-1 only for seepage at maturity and harvest. Soil N distribution varied according to weather conditions, and decision-makers should consider rainfall events before N fertilizer managements.