施氮对单作和套作小麦产量和氮素利用特征的影响

小麦/玉米套作是四川主要的旱作模式,研究小麦的氮素吸收利用效率及套作玉米对小麦的影响有助于进一步提示套作小麦的增产优势、养分高效利用及了解玉米小麦间相互作用机理。本研究通过田间试验研究了不同氮水平下0 kg(N)·hm-2、60 kg(N)·hm-2、120 kg(N)·hm-2和180 kg(N)·hm-2,分别记为N1、N2、N3和N4]小麦单作、小麦/空带和小麦/玉米套作3种模式中小麦的产量、氮素吸收利用特征和玉米对小麦的影响。结果表明:在不同的氮处理下,与单作小麦相比,小麦玉米套作的小麦始终表现出明显的产量优势,其生物量和籽粒产量比单作小麦平均增加15.7%和17.8%;套作小麦边行优势明显,其边行的地上部生物量、产量、吸氮量和氮肥偏生产力比单作行分别增加23.8%、27.3%、48.9%和19.1%,说明套作小麦比单作小麦对氮利用效率更高。不施氮(N1)和低氮(N2)处理小麦/玉米套作模式中小麦的生物量、产量比小麦/空带模式平均低6.5%和5.7%,但在中氮水平(N3)时小麦/玉米套作模式中小麦产量、地上部生物量、地上部吸氮量和氮肥偏生产力分别比小麦/空带模式高14.1%、5.0%、6.8%和4.5%。说明在小麦/玉米套作模式中套入玉米在施氮不足时小麦生长受到抑制,而在施氮充足时小麦生长得到促进。因此,套作小麦有边行优势和产量优势,小麦行间套作玉米时需要配施一定量的氮肥以消除小麦、玉米间的氮素竞争从而促进小麦的生长。

Wheat grain yield and nitrogen use characteristics under monoculture and intercropping with different nitrogen fertilization rates

Wheat/maize relay-intercropping system is an important rainfed planting pattern in Sichuan Province, China. It is therefore important to investigate rational nitrogen management strategies to improve not only productivity and nutrient use efficiency, but also to explore the yield advantage mechanism of the interaction between intercropped wheat and maize. In this direction, a field experiment was conducted in 2014 involving four nitrogen application rates (0 kg.hm^-2, 60 kg.hm^-2, 120 kg.hm^-2 and 180 kg.hm^-2, denoted by N1, N2, N3 and N4, respectively) under three planting patterns. The planting patterns included wheat monoculture (W), wheat/maize strip relay-intercropping (W/M) and wheat/empty strip (W/E) at an experimental research base in Chongzhou, Sichuan. Grain yield, biomass, nitrogen uptake, nitrogen use efficiency and partial factor productivity of nitrogen (PFP-N) of wheat were calculated. The results showed that 1) intercropped wheat had yield advantage over monoculture wheat under all the nitrogen application rates. The aboveground biomass and grain yield of intercropped wheat in W/M and W/E treatments were on average 15.7% and 17.8% higher than that of monoculture wheat. 2) Border row wheat had advantage in terms of productivity, nitrogen uptake and nutrient use efficiency. Aboveground biomass, yield, nitrogen uptake and PFP-N of the border row wheat were 23.8%, 27.3%, 48.9% and 19.1% higher than those of monoculture wheat, respectively. It suggested that intercropped wheat had higher nitrogen use efficiency with higher grain yield compared to monoculture wheat. 3) Compared to W/E pattern, aboveground biomass and grain yield of wheat under W/M pattern dropped by 6.5% and 5.7% under the zero and 60 kg.hm^-2 nitrogen application treatments, respectively. However, under the medium nitrogen application rate (N3, 120 kg.hm^-2) grain yield, aboveground biomass, shoot nitrogen uptake and PFP-N of wheat under W/M were 14.1%, 5.0%, 6.8% and 4.5% higher than those under W/E, respectively. These results indicated that intercropped wheat may be inhibited by intercropping maize under low nitrogen application rate (such as low than 60 kg.hm^-2), in contrast wheat development in intercropping could be promoted by sufficient nitrogen application. Furthermore, intercropped wheat had advantages in grain yield and nutrient use efficiency, especially for border row plants. Although maize and wheat interaction enhanced this process, sufficient nitrogen fertilizer application in maize and wheat was critical for promoting growth of relay-intercropped wheat.