Fertilizer management practices that focus on applying N fertilizer at the right rate and time have been proposed as a practical option to reduce NO3 -N losses from subsurface drained agricultural fields. In this study, regression equations were developed to predict NO3 -N losses for a corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation in southern Minnesota, using fertilizer application timing and rate and growing season precipitation as inputs. The equations were developed using the results of the field-scale hydrologic and N simulation model DRAINMOD-NII, first calibrated and validated for three sites in southern Minnesota, and then run with different combinations of N fertilizer application rates and timings. Fertilizer timing treatments included a single application in the fall or spring and a split-spring application (half applied preplant and the remaining applied as sidedress). The predictive regression equations showed that the split fertilizer application timing could reduce regional N loads by 28% compared with spring or fall applications. Greater reductions were predicted when the split timing was combined with lower N fertilizer rates. Utilizing the split application timing and reducing the fertilizer rate by 10 and 30% showed 33 and 41% reductions in N loads, respectively, compared with current fertilizer management practices. Such reductions in fertilizer application rates could be achieved through the use of variable-rate nitrogen (VRN) fertilizer technologies. Results of this modeling study indicate that synchronizing fertilizer application with crop requirements and utilizing VRN technologies could significantly reduce N loads to surface waters in southern Minnesota.

中文翻译：

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明尼苏达州南部地下排水中硝酸盐-N 负荷作为施肥率和时间的函数的区域预测

以正确的比例和时间施用氮肥为重点的肥料管理实践已被提议作为减少地下排水农田中 NO3 -N 损失的实用选择。在这项研究中，开发了回归方程来预测明尼苏达州南部玉米 (Zea mays L.) 和大豆 [Glycine max (L.) Merr.] 轮作的 NO3 -N 损失，使用施肥时间和速率以及生长季节降水作为输入。这些方程是使用田间水文和 N 模拟模型 DRAINMOD-NII 的结果开发的，首先对明尼苏达州南部的三个地点进行校准和验证，然后使用不同的 N 肥料施用率和时间组合运行。施肥时间处理包括在秋季或春季单次施肥和分春施肥（一半施于植前，其余施作侧施）。预测回归方程表明，与春季或秋季施用相比，分批施肥时间可以将区域氮负荷降低 28%。当分割时间与较低的施氮量相结合时，预计会出现更大的减少。与当前的施肥管理实践相比，利用分批施肥时间和将施肥量降低 10% 和 30% 分别显示氮负荷减少 33% 和 41%。可以通过使用可变速率氮肥 (VRN) 施肥技术来降低施肥量。