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.

中文翻译：

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灌溉策略和氮肥用量对玉米生长和粮食产量的影响

在北佛罗里达，氮负荷增加和水质下降已成为一个主要问题，部分原因是农业等人为非点源活动。本研究的主要目的是调查灌溉策略和氮 (N) 肥力对沙质土壤中玉米生物量、产量和水分生产力的影响。田间试验于 2015-2017 年在佛罗里达州 Live Oak 进行，使用随机完整区组，采用裂区设计和四个重复。处理评估了五种灌溉策略：(i) GROW，模仿该地区种植者的灌溉做法，(ii) SWB，使用土壤水分平衡来安排灌溉；(iii) SMS，使用土壤湿度传感器来安排灌溉；(iv) RED，应用 60% 的 GROW 处理；(v) NON、非灌溉和三个 N 生育率：(i) 低 (157 kg N/ha)，(ii) 中 (247 kg N/ha)，和 (iii) 高 (336 kg N/ha)。与 GROW 相比，SWB、SMS 和 RED 灌溉处理在最终生物量、氮吸收和谷物产量方面没有差异；然而，这些处理分别平均减少了 41%、47% 和 36% 的灌溉量，而在所评估的三个玉米季节期间对产量没有影响。对于大多数变量，在低氮率和高氮率之间发现了统计差异，但与中等氮率相比没有差异。与高施氮率相比，使用中等施氮率可减少 26% 的施氮量，而对氮吸收、生物量和产量没有负面影响。在本次试验中，玉米吸氮量达到了平台期；因此，潜在的氮损失是由于应用超过推荐的比率而导致的。此外，这些更有效的灌溉和氮肥管理策略的实施减少了灌溉和氮肥的施用，而不会对产量产生负面影响。因此，这些做法可以防止潜在的氮渗入水体，同时提高利润。