不同滴灌施肥方式下棉花根区的水、盐和氮素分布

 【目的】探讨不同滴灌施肥方式下土壤水、盐、氮和棉花根系的分布，对于滴灌条件下水肥盐的合理调控具有重要意义。【方法】在温室条件下应用15N标记尿素进行了不同滴灌施肥方式对土壤水、盐和氮素分布的影响及其与棉花根系分布之间关系的盆栽试验。根据滴灌灌水（W）和施肥（N）的先后顺序，设置4种不同氮肥施用方式：①氮肥在一次灌溉过程的前期施用（N-W）;②后期（W-N）;③中间（W-N-W）;④全程施用（NW）。同时以传统的氮肥直接施入土壤后浇灌（SN-W）为对照。【结果】土壤水盐分布明显受灌溉方式的影响，但滴灌条件下不同施肥方式对土壤水盐分布无影响。氮肥滴灌施肥24 h后15N主要分布在0～20 cm深度土层，但不同施肥方式之间差异明显。NW处理15N在土壤中的垂直分布最深，但水平分布范围较小，且收获后土壤硝态氮在下层大量积累，容易造成淋失。相比之下，N-W处理15N在0～20 cm土层分布最均匀，收获后土壤硝态氮的残留量也最小，且棉花根系的生长和分布也优于其它处理。【结论】滴灌条件下，氮肥在一次灌溉过程的前期施用有利于提高氮肥利用率，减少氮素的淋洗损失。

Distributions of Water, Salinity, and Nitrogen in Cotton Root Zone by Different Fertigation Strategies

【Objective】It is of great importance to study the distributions of water, sanility and nitrogen in soil and cotton root for optimizing soil salinity, irrigation and fertilization strategies with drip irrigation. 【Method】Spatial distributions of water, salinity and nitrogen in cotton root zone were investigated in a pot experiment with different irrigation and fertilization methods under greenhouse conditions. According to the application order of nitrogen (N) fertilizer solution and water (W) involved in an irrigation cycle, four fertigation treatments were designed, nitrogen applied 1) in the beginning of the irrigation cycle (N-W), 2) at the end (W-N), 3) in the middle (W-N-W), and 4) throughout the irrigation cycle (NW). Conventional nitrogen fertilizer broadcasted in soil following surface irrigation was the control (SN-W). 【Result】Distributions of water and salinity in soil were significantly influenced by irrigation methods, but no differences were found between the four nitrogen fertigation strategies. 15N in the soil profile was concentrated at depth 0-20 cm 24 h after fertigation, and the distribution of %15N atoms in soil was significantly influenced by the different fertigation strategies. In strategy NW, 15N in the soil moved deeper and there was less lateral movement 24 h after fertigation than in the other treatments, and significant amounts of residual soil nitrate were found in deeper soil layers after harvest. In contrast, nitrogen was more evenly distributed at 0-20 cm depth 24 h after a fertigation cycle and fewer nitrates were left at the end of experiment after N-W treatment, and furthermore, the distribution of roots with N-W treatment was also better. 【Conclusion】These results suggest that the N-W strategy would work better in increasing nutrient-use efficiency, and reducing the risk of chemical leaching from the root zone.