一穴多株种植对夏玉米群体质量和产量的影响

Effects of more plants per hill on population quality and yield of summer maize

增加种植密度是玉米高产的重要手段,但是种植密度的持续增加也带来一系列问题,其中高密群体的郁闭问题已成为限制进一步增加种植密度的主要因素之一。为缓解夏玉米高密度群体的郁闭状况,改善高密度种植下的玉米群体质量和产量形成,本试验在82 500株·hm·2密度下设置了一穴1株（P1）、一穴2株（P2）和一穴3株（P3）3个处理,分析了一穴多株对夏玉米各生育时期的叶面积、干物质、光合势、相对生长率、净同化率、作物生长速率、粒叶比和产量的影响。结果表明,与对照P1相比,P2和P3吐丝期单株叶面积分别增加10.7%~21.9%和7.3%~16.7%,吐丝后20 d分别增加13.5%~21.9%和9.4%~12.7%;P2和P3吐丝期和成熟期干物质积累显著高于P1（P〈0.05）。一穴多株种植提高了夏玉米6叶展以后的光合势,P2的提高幅度小于P3;P2、P3吐丝后20 d到成熟期相对生长率比P1分别高30.4%~190.7%和33.9%~183.5%,净同化率分别高16.1%~161.9%和30.7%~155.8%。采用一穴多株种植可以提高作物的生长速率、粒叶比和籽粒产量,P2和P3分别比P1增产5.8%~23.5%和4.9%~18.9%。粒重/叶面积、粒数/叶面积与籽粒产量呈显著直线正相关（R2=0.94,P〈0.000 1和R2=0.76,P〈0.001）。可见,在高密种植条件下,采用一穴多株种植可以改善夏玉米群体质量、提高产量。本研究推荐高密度下一穴2株种植方式。

It is important to get high maize yield by increasing planting density, but this could have some shortfalls（e.g.,canopy closure） which limit further increase in planting density. In order to alleviate canopy closure of summer maize under high density and to improve population quality and yield, a 2-year field experiment was conducted at the Wuqiao Experimental Station of China Agricultural University. Three treatments were designed in the field, including one plant per hill（P1）, two plants per hill（P2）, and three plants per hill（P3） under planting density of 82 500 plant·hm·2. Then the study estimated leaf area per plant, dry matter（DM）, photosynthetic potential（PP）, relative growth rate（RGR）, net assimilation rate（NAR）, crop growth rate（CGR）, grain-leaf area ratio and grain yield. Leaf areas under P2 and P3 treatments at silking stage（R1） increased by 10.7% ·21.9% and 7.3% ·16.7%, respectively. At about 20 days after silking（DAS）, leaf areas under P2 and P3 treatments increased by 13.5% ·21.9% and 9.4% ·12.7%, respectively, compared with P1 treatment. The DM of P2 and P3 treatments at R1 and physiological maturity stage（M） was significantly higher（P 〈 0.05） than that of P1 treatment. PP was improved at6-leaf stage under P2 treatment, but decreased with increasing number of plants per hill. Compared with P1 treatment, RGRfrom DAS20 to M increased by 30.4% ·190.7% and 33.9% ·183.5%, NAR increased by 16.1% ·161.9% and 30.7% ·155.8%,respectively, under P2 and P3 treatments. Also CGR, grain-leaf area ratio and grain yield were enhanced under P2 and P3 treatments. Compared with P1 treatment, yield under P2 and P3 treatments increased by 5.8% - 23.5% and 4.9% - 18.9%,respectively. It was noted that ear number per hectare and grain number per ear under P2 treatment slightly increased and the thousand-grain weight increased obviously over that of P1 treatment. Analysis of ear number per hectare, grain number per ear and thousand-grain weight after two years of growth showed that ear number per hectare dropped slightly, grain number per ear increased slightly, and thousand-grain weight evidently increased under P3 treatment, compared with P1 treatment. Yield showed significant and positive linear correlation with grain weight/leaf area ratio（R2 = 0.94＊＊＊＊） and grain number/leaf area ratio（R2 = 0.76＊＊＊）. Thus under high density conditions, more plants per hill improved the processes of leaf area and dry matter accumulation that in turn improved population quality. The increment in grain yield under more plants per hill was mainly due to the enhancements of thousand-grain weight and grain number per ear. In conclusion, population quality, yield and yield components were improved in two plants per hill treatment. Thus based on this study, two plants per hill planting pattern was recommended as the best performing planting pattern of maize.