SWAT model instances for "Groundwater impacts of adding carrot to corn-peanut rotations in North Florida"

The Upper Floridan aquifer underlying the Suwannee River Basin in Florida has experienced increased groundwater pumping and nitrate leaching over the last half century resulting in violation of water quantity and quality standards, largely due to row crop production. Increasingly carrot is being added as a winter cash crop to the traditional corn-peanut rotation in the region which may further increase pumping and nitrogen leaching. Establishing carrot nitrogen and irrigation best management practices is therefore critical to help growers meet yield goals while minimizing groundwater quantity and quality impacts. In this study, a carrot cultivation field experiment was conducted to evaluate the effects of a range of irrigation and nitrogen fertilizer practices on irrigation demand, nitrogen uptake and carrot crop growth and yield. Results showed that soil moisture sensor-based irrigation reduced the amount of water used for carrot cultivation by approximately 30% over the calendar-based irrigation without statistically significant reductions in yield, and fertilization rates above 224 kg ha-1 showed no statistically significant increase in yield. A field-scale SWAT carrot model was calibrated using the field experiment data and validated using previously published experimental results. The carrot parameters were then incorporated into a watershed-scale SWAT model of the Santa Fe River Basin, a tributary of the Suwannee River, and used to assess groundwater recharge and nitrate leaching impacts of adding carrot into corn-peanut rotations across all row crop lands in the watershed. Modeling results showed that adding carrot cultivation to the rotation will increase irrigation by 32-43% and decrease net groundwater recharge from row crop land by 9-28%. Moreover, it will increase nitrate leaching from row crop land by 60-100%. These results indicate that adding carrot cultivation to the conventional corn-peanut rotation will make water quantity and quality standards in the region more difficult to achieve.

佛罗里达州苏万尼河流域（Suwannee River Basin）下方的上佛罗里达含水层（Upper Floridan aquifer），在过去半个世纪中因大田作物生产，地下水开采量和硝酸盐淋失量持续增加，导致其水量和水质标准遭到破坏。该地区传统的玉米-花生轮作体系中，胡萝卜正逐渐被作为冬季经济作物纳入种植，这可能进一步加剧地下水开采和氮淋失。因此，制定胡萝卜的氮素与灌溉最佳管理实践（best management practices）至关重要，以助力种植者在实现产量目标的同时，最大限度降低对地下水量和水质的影响。本研究通过开展胡萝卜种植田间试验，评估了不同灌溉和氮肥施用方式对灌溉需求、氮吸收以及胡萝卜生长和产量的影响。结果表明，基于土壤湿度传感器的灌溉方式相较于基于日历的灌溉方式，可减少约30%的胡萝卜种植用水量，且产量未出现统计学意义上的显著下降；而当施肥量超过224千克/公顷时，产量也未呈现统计学意义上的显著提升。研究人员利用田间试验数据对田间尺度的SWAT胡萝卜模型（Soil and Water Assessment Tool）进行了校准，并通过已发表的试验结果对其进行了验证。随后，将胡萝卜相关参数纳入苏万尼河支流圣菲河流域（Santa Fe River Basin）的流域尺度SWAT模型中，用于评估在流域内所有大田作物土地上将胡萝卜纳入玉米-花生轮作体系后，对地下水补给和硝酸盐淋失的影响。模型模拟结果显示，将胡萝卜纳入轮作体系将使灌溉量增加32%-43%，并使大田作物土地的地下水净补给量减少9%-28%；此外，还会使大田作物土地的硝酸盐淋失量增加60%-100%。这些结果表明，在传统玉米-花生轮作中加入胡萝卜种植，将使该地区的水量和水质标准更难达成。