水肥不同层次组合对冬小麦(Triticum aestivum L．)氮磷养分有效性和产量效应的影响

Effects of water and fertilizer spatial coupling on nitrogen and phosphorus validity and yield effect of winter wheat (Triticum aestivum L.)

以肥熟土垫旱耕人为土为供试土样，用分层土柱试验法研究了不同层次水分、氮、磷组合对冬小麦（Triticum aestivum L．）氮磷养分有效性和产量效应的影响。结果表明，不同土层水肥处理的氮磷养分有效性和产量效应差异显著。氮素养分有效性在4．73％-41．19％之间，磷素养分有效性在4．11％-13．58％之间。对氮素养分有效性，单施氮整体湿润时（0-90cm土层湿润）较上干下湿（0-30cm土层干旱胁迫，30-90cm土层湿润）低4．87％，而氮磷配施在整体湿润时较上干下湿高6．38％，差异均达显著水平；对磷素养分有效性，氮磷配施时，在整体湿润时较上干下湿增加5．01T（P〈0．05）。从不同施肥土层看，氮素养分有效性均以0-90cm土层施肥处理最高；对氮磷配施处理，在上干下湿时分别比0-30cm、30-60cm和60-90cm土层施肥处理高9．5％、10．1％和20．2个％；对磷素养分有效性，整体湿润处理，以0-30cm土层施肥显著高于其它土层施肥处理。单施氮或磷，上干下湿时氮磷养分的产量效应均高于整体湿润处理，但氮磷配施时均以整体湿润处理较高；从不同土层施肥看，氮素养分的产量效应以0-90cm土层施肥最高；磷素养分的产量效应则表现为0-90cm与0-30cm土层施肥处理显著高于30-60cm和60-90cm土层施肥处理。分析0-90cm土层残留硝态氮和有效磷累积量可以看出，不同处理土壤残留硝态氮含量存在显著差异，上干下湿时CK、单施氮、单施磷和氮磷配施土壤残留硝态氮分别比整体湿润相应施肥处理增加125．8％、20．1％、21．9％和2．1％；不同处理有效磷差异性不及硝态氮明显。整体看，在两种水分状况下，均以0-90cm和0-30cm土层施肥有利于提高氮磷养分对冬小麦的有效性和产量效应，减少硝态氮和有效磷在土壤中的残留累积。考虑到生产上的可操作性，仍以施人0-30cm土层最适，说明即使在上千下湿情况下，保证上层有效养分供应仍具重要作用。

A column experiment was conducted with a Eum-Orthic Anthrosol （ Cinnamon soil） to study the effect of spatial coupling of water, nitrogen and phosphorus on nitrogen and phosphorus validity and yield effect of winter wheat （ Triticum aestivum L. ）. The column consisted of three layers. Each soil layer was 30cm thick and there was a 2cm layer of coarse sand between the layers to prevent water and nutrients exchange. The results showed that there was large difference between nitrogen validity and phosphorus validity of wheat among different treatments. Nitrogen validity ranged from 4.73%-41.19% compared to phosphorus validity of 4.11%-13.58%. The yield effect of phosphorus was higher than nitrogen. When only nitrogen fertilizer （ N treatment） was applied to the column, nitrogen validity was 4.87 percent lower in the wet treatment （entire column was at 75%-80% of field capacity） compared to the dry treatment （0-30 cm layer at 40%-45% of field capacity, 30-90 cm layer at 75%-80% of field capacity）. In comparison, when both nitrogen and phosphorus fertilizer （NP treatment） were applied to the column, nitrogen validity was 6.38 percent higher in the wet treatment compared to the dry treatment. There was no significant difference in the phosphorus validity of the wet and dry treatments when only phosphorus fertilizer （P treatment） was applied, but phosphorus validity was 5.01 percent higher in the wet treatment compared to the dry treatment when nitrogen and phosphorus fertilizer were applied together （p 〈 0.05 ）. This showed that increased soil water content in the 0-30cm soil layer could improve nitrogen validity and phosphorus validity in the NP treatment. A comparison was also made to determine the effect of fertilizer placement on nutrient validity. In both the wet and dry soil treatments, nitrogen validity in the N and NP treatments was highest when the fertilizer was applied to the entire soil column （0-90cm）. In the dry soil, nitrogen validity was 9.5 percent lower when fertilizer was placed only in the 0-30 cm layer compared to when the fertilizer was applied to the entire soil column, 10.1 percent lower when fertilizer was placed only in the 30-60 cm layer, and 20.2 percent lower when fertilizer was placed only in the 60-90 cm layer. In the wet soil treatment, phosphorus validity was highest when both nitrogen and phosphorus fertilizer were applied to the 0-30cm layer. The yield effect of nitrogen and phosphorus were higher in the dry soil compared to wet soil in the N and P treatments. In contrast, for the NP treatment, the yield effect of nitrogen and phosphorus were higher in the wet soil compared to the dry soil. The yield effect of nitrogen was highest when nitrogen or nitrogen and phosphorus were applied to the entire soil column. The yield effect of phosphorus was highest when phosphorus was applied to the entire column in the dry soil treatment, but for the wet soil, the yield effect of phosphorus was higher in the NP treatment when the fertilizer was only applied to the 0-30cm layer. Residual amounts of effective nitrogen and phosphorus of 0-90 cm soil layer were analyzed too. The result showed that there were significant differences of residual amounts of effective nitrogen among different treatments. Residual amounts of effective nitrogen of CK, N treatment, P treatment and NP treatment were 125.8, 20. 1, 21.9 and 2.1 percent higher in the dry treatment compared to in the wet treatment. The difference of effective phosphorus among different treatments was insignificant. Overall, fertilizer validity and yield effect were higher and residual fertilizer levels were lower when fertilizer was applied from 0-90 or from 0-30 cm, regardless of soil water content. In actual practice, it is important to maintain a high level of available nutrients in the 0-30cm soil layer even under dry topsoil conditions.