覆盖作物和氮素用量对玉米产量及光合特性的影响

通过2种覆盖作物和5个氮素用量大田试验,探讨氮素和覆盖作物对玉米产量和光合特性的影响。随氮素用量增加,玉米产量先升高后趋于稳定,75 kg/hm²氮处理有效穗数最大,225 kg/hm²氮处理穗粒数和百粒重最大;低氮水平下,黑麦覆盖玉米产量最大。覆盖作物增加玉米花后20 d前的叶绿素含量,且提高了高氮处理开花后20～40 d的叶片光合速率;黑麦覆盖显著增加玉米中、上部叶面积。光能利用差异主要在花后40 d,氮素用量225～300 kg/hm²时黑麦覆盖最大光化学效率(F_v/F_m)、光化学淬灭(qP)和表观电子传递速率(ETR)均高于玉米单作。综上,玉米-覆盖作物系统的玉米低氮量处理增产幅度大,高氮量处理产量高;以黑麦覆盖处理较好。

Effect of Cover Crops and Nitrogen Application Rate on Maize Yield and Photosynthetic Characteristics

A two-factor, two cover crops(CC:Brassica napus and Secale) and five nitrogen rate(N:0, 75, 150, 225, 300 kg/ha), randomized block experiment was conducted to investigate the effects of N rate and CC on maize yield and photosynthetic characteristics in a CC-maize system. The results indicated that maize yield initially increased with increasing N rate. For both CC, the highest number of effective ears was observed at 75 kg/ha, while the highest number of grains per ear and 100-kernel weight were observed at 225 kg/ha. Under low N rate, the highest maize yield were observed, in the Secale treatment. CC increased the pigment content 20 days before tasselling, and increased photosynthetic rate under higher N rate 40 days after tasselling. Particularly, the Secale treatment significantly increased the leaf area of the middle and upper leaves. Differences in light utilization were mainly observed 40 days after flowering. At N rate of 225-300 kg/ha, the Secale treatment exhibited the highest maximum photochemical efficiency(F_v/F_m), photochemical quenching(qP), and apparent electron transport rate(ETR) compared to CK. Conclusively, the N rate and CC remarkably enhanced the increase amplitude of yield under the lower N rate and increased the yield under the higher N rate. The CC improved maize yield in the second year, and Secale was recommended.