Abstract Comparisons of variable rate irrigation (VRI) and variable rate fertigation (VRF) with fixed rate irrigation (FRI), no irrigation (NI) and conventional fertilizer management for maize (Zea mays L.) under three soil types (S1, S2 and S3) were made for three years (2015, 2016 and 2017). The research quantified and compared maize growth and development [leaf area index (LAI) and plant height], grain yield, crop evapotranspiration (ETc), irrigation-yield production functions (IYPF), evapotranspiration-yield production functions (ETYPF) and crop water productivity (CWP) under VRI, FRI and NI at fixed rate fertigation (FRF), VRF and pre-plant nitrogen (PP) management in the same environment and under the same agroomic management practices. The VRF treatment used 20% less fertilizer as compred with PP and FRF treatment without significantly (P > 0.05) reducing the grain yield. In the higher elevation soil S1, the grain yield was not significantly different (P > 0.05) between FRI and VRI treatments. However, in S2 and S3 which have lower elevation, yield in FRI was 43% and 55% greater than the yield in VRI, respectively. On average, under VRI management total irrigation amount 24% lower than FRI in S1, with only 4% reduction in yield as compared with FRI. Soil type impacted the response of maize grain yield to ETc and the responses also varied between FRI and VRI. For all soil types and years, higher ETc was observed in FRI treatment, except in 2015 for S1 and S2 where highest ETc was observed in VRI. FRI had greater productivity per unit of ETc than VRI. Observing the linear relationship of the pooled data for each soil type, a 25.4 mm of ETc (beyond the intercept) resulted in 0.48 and 0.35 ton ha−1 maize yield for FRI and VRI treatment, respectively, in S1; 0.75 and 0.45 ton ha−1 for FRI and VRI, respectively, in S2; and 0.71 and 0.43 ton ha−1 for FRI and VRI, respectively, in S3. VRI strategy increased the variability in grain yield, ETc and CWP as compared with FRI management. S1 had the lowest grain yield variability as compared with S2 and S3. The coefficient of variation (CV) of grain yield ranged from 8% in S1-FRI to as high as 35.3% in S3 VRI. FRI treatment in all soil types and years had less variation in yield as compared with VRI. Soil type had impact on CWP. On a three-year average basis, CWP was 2% higher in VRI in S1 whereas 11% lower in S2 and S3 than FRI CWP. Stronger grain yield response to irrigation and ETc (IYPF and ETYPF) were observed for FRI than VRI and NI at all nitrogen levels. The results of this research indicated that, in most cases, FRI had superior performance in terms of maintaining optimum crop yield and reducing yield variations than VRI. VRI management based on soil water status has potential of maintaining maize grain yield and improving CWP as compared with FRI in certain conditions or soil types such as in S1. However, further research is needed to validate/justify its adoption for the fields with significant spatial soil heterogeneity (both in horizontal and vertical domains) and to understand the economics of VRI-VRF systems. These results would be beneficial for maize growers and their advisors in terms of understanding the productivity responses to water under VRI and FRI management strategies with VRF, FRF and PP nitrogen application.

中文翻译：

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不同土壤类型玉米可变和固定速率灌溉和氮管理的比较分析：第二部分。生长、粮食产量、蒸散量、生产函数和水分生产力

摘要 玉米（Zea mays L.）在三种土壤类型（S1、S2 和S3) 制作了三年（2015、2016 和 2017）。该研究量化并比较了玉米生长发育[叶面积指数 (LAI) 和株高]、粮食产量、作物蒸散量 (ETc)、灌溉产量生产函数 (IYPF)、蒸散量产量生产函数 (ETYPF) 和作物水分在 VRI、FRI 和 NI 下以固定比率施肥 (FRF)、VRF 和植前氮 (PP) 管理在相同的环境和相同的农业管理实践下提高生产力 (CWP)。与 PP 和 FRF 处理相比，VRF 处理使用的肥料减少了 20%，但没有显着（P > 0.05）降低谷物产量。在高海拔土壤 S1 中，FRI 和 VRI 处理之间的谷物产量没有显着差异（P > 0.05）。然而，在海拔较低的 S2 和 S3 中，FRI 的产量分别比 VRI 的产量高 43% 和 55%。平均而言，在 VRI 管理下，S1 的总灌溉量比 FRI 低 24%，与 FRI 相比，产量仅降低 4%。土壤类型影响玉米产量对 ETc 的响应，并且响应在 FRI 和 VRI 之间也有所不同。对于所有土壤类型和年份，在 FRI 处理中观察到更高的 ETc，除了 2015 年在 S1 和 S2 中，在 VRI 中观察到最高的 ETc。FRI 每单位 ETc 的生产率高于 VRI。观察每种土壤类型汇总数据的线性关系，在 S1 中，25.4 毫米的 ETc（超出截距）导致 FRI 和 VRI 处理的玉米产量分别为 0.48 和 0.35 吨 ha-1；S2 中 FRI 和 VRI 分别为 0.75 和 0.45 吨 ha-1；在 S3 中，FRI 和 VRI 分别为 0.71 和 0.43 吨 ha-1。与 FRI 管理相比，VRI 策略增加了谷物产量、ETc 和 CWP 的变异性。与 S2 和 S3 相比，S1 的谷物产量变异性最低。谷物产量的变异系数 (CV) 从 S1-FRI 的 8% 到 S3 VRI 的高达 35.3%。与 VRI 相比，所有土壤类型和年份的 FRI 处理的产量变化较小。土壤类型对 CWP 有影响。在三年平均基础上，S1 中 VRI 的 CWP 比 FRI CWP 高 2%，而 S2 和 S3 中的 CWP 低 11%。在所有氮水平下，FRI 对灌溉和 ETc（IYPF 和 ETYPF）的谷物产量响应比 VRI 和 NI 更强。这项研究的结果表明，在大多数情况下，FRI 在保持最佳作物产量和减少产量变化方面比 VRI 具有更好的性能。在某些条件或土壤类型（如 S1）下，与 FRI 相比，基于土壤水分状况的 VRI 管理具有保持玉米产量和提高 CWP 的潜力。然而，需要进一步的研究来验证/证明其在具有显着空间土壤异质性（水平和垂直领域）的领域的采用，并了解 VRI-VRF 系统的经济性。