Soil and Water Science Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, United States of America.
Agronomy Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, United States of America.
PLoS One. 2015 Jan 30;10(1):e0117891. doi: 10.1371/journal.pone.0117891. eCollection 2015.
Recent increases in nitrate concentrations in the Suwannee River and associated springs in northern Florida have raised concerns over the contributions of non-point sources. The Middle Suwannee River Basin (MSRB) is of special concern because of prevalent karst topography, unconfined aquifers and sandy soils which increase vulnerability of the ground water contamination from agricultural operations--a billion dollar industry in this region. Potato (Solanum tuberosum L.) production poses a challenge in the area due to the shallow root system of potato plants, and low water and nutrient holding capacity of the sandy soils. A four-year monitoring study for potato production on sandy soil was conducted on a commercial farm located in the MSRB to identify major nitrogen (N) loss pathways and determine their contribution to the total environmental N load, using a partial N budget approach and the potato model SUBSTOR. Model simulated environmental N loading rates were found to lie within one standard deviation of the observed values and identified leaching loss of N as the major sink representing 25 to 38% (or 85 to 138 kg ha(-1) N) of the total input N (310 to 349 kg ha(-1) N). The crop residues left in the field after tuber harvest represented a significant amount of N (64 to 110 kg ha(-1) N) and posed potential for indirect leaching loss of N upon their mineralization and the absence of subsequent cover crops. Typically, two months of fallow period exits between harvest of tubers and planting of the fall row crop (silage corn). The fallow period is characterized by summer rains which pose a threat to N released from rapidly mineralizing potato vines. Strategies to reduce N loading into the groundwater from potato production must focus on development and adoption of best management practices aimed on reducing direct as well as indirect N leaching losses.
最近，佛罗里达州北部的苏万尼河及其相关泉水中硝酸盐浓度的增加引起了人们对非点源贡献的关注。由于普遍存在的喀斯特地形、无约束含水层和沙质土壤，中苏万尼河流域（MSRB）特别令人担忧，这增加了农业活动对地下水污染的脆弱性——该地区是一个价值 10 亿美元的产业。由于马铃薯（Solanum tuberosum L.）植物根系浅，沙质土壤的保水和保肥能力低，该地区的马铃薯生产面临挑战。在 MSRB 地区的一个商业农场，对沙质土壤上的马铃薯生产进行了为期四年的监测研究，采用部分氮预算法和马铃薯模型 SUBSTOR，确定了主要的氮（N）损失途径，并确定了它们对总环境 N 负荷的贡献。模型模拟的环境 N 加载率与观测值相差一个标准差，确定淋失损失 N 是主要的汇，占总输入 N（310 至 349kg/ha N）的 25%至 38%（或 85 至 138kg/ha N）。块茎收获后留在田间的作物残体代表了大量的 N（64 至 110kg/ha N），并且在它们矿化后以及没有随后的覆盖作物时，存在潜在的间接淋失 N 的风险。通常，在块茎收获和秋季种植青贮玉米之间有两个月的休耕期。休耕期的特点是夏季降雨，这对迅速矿化的马铃薯藤释放的 N 构成威胁。减少马铃薯生产中 N 向地下水加载的策略必须侧重于开发和采用旨在减少直接和间接淋失 N 损失的最佳管理实践。
