滴灌系统运行方式和施肥频率对番茄根区土壤氮素动态的影响

在日光温室内开展田间试验，研究了滴灌施肥灌溉系统运行方式和施肥频率对番茄根区硝态氮在生育期内随时间的变化动态、空间分布特征以及氮肥利用效率和回收率的影响。系统运行方式包括不同灌水和施肥次序组成的3种方案。结果表明，在整个生育期内，在灌溉过程的前期施肥，硝态氮在各土层中的分配较为均匀；随着施肥次序向后推移，硝态氮在0～20cm土层的累积逐渐明显。随着施肥频率降低，硝态氮在生育期内随时间的变化逐渐加剧。在滴头的周围，硝态氮易随水流运动，并在湿润土体的横向边缘产生累积。随着施肥次序向前推移，硝态氮向湿润土体边缘运移的趋势愈加明显。剖面内的硝态氮总量随着施肥频率的降低而降低。随着施肥次序向后推移，氮回收率逐渐增大，氮肥利用效率逐渐减小。氮肥利用效率随施肥频率提高而增加。在滴灌施肥灌溉条件下，运行方式选用最初灌溉总时间的1／4时间灌水，再用1／2时间施肥，最后用1／4时间冲洗管道，施肥频率取每周一次较为适宜。

Nitrogen dynamics in soil as affected by fertigation strategies and frequencies for drip irrigated tomato

Field experiments were conducted in a solar-heated greenhouse with drip-irrigated tomato to investigate the effects of drip fertigation strategy and frequency on nitrate dynamics, spatial distribution of nitrate, apparent recovery of nitrogen and fertilizer use efficiency in growing season. The results showed that the strategy of applying nutrient at the beginning resulted in a uniform distribution of nitrate in different layers and nitrate in upper layers increased as the fertilization time was transferred towards the end of an irrigation cycle. Nitrate varied more unevenly as frequency decreased during the growing season. Nitrate accumulated at the lateral boundary of the wetted volume, but no significant accumulation was found at the vertical boundary. As the fertilization time was transferred towards the beginning of an irrigation cycle, potential of nitrate moving towards the boundary of wetted volume was more obviously. Accumulation of nitrate in the profile declined with fertilization frequency. Fertilizer use efficiency declined as the fertilization time was transferred towards the end of an irrigation cycle. On this basis, the optimal fertilization strategy was suggested.