| Winter wheat-summer maize rotation is an important cropping system in northern China.Farmland production continues to be highly dependent on the use of chemical fertilizers,which has led to the reduction of fertilizer use efficiency and soil quality.As a natural fertilizer source,green manure crops can replace the use of chemical fertilizers.It is necessary to explore the utilization of green manure in double cropping farmland to achieve stable yield and nitrogen reduction.This study was conducted in the Guanzhong Plain(Yangling),a typical wheat-maize rotation area.Four different intercropping patterns of green manure small black bean and summer maize were set up,including maize and small black bean 1: 1 intercropping(M1S1),2: 1 intercropping(M2S1),2: 2 intercropping(M2S2)and maize monoculture(CKM).The productivity and intercropping effects of different intercropping systems were studied without changing the planting density of summer maize.Through two years of experiments,the following main conclusions are drawn:(1)Compared with monoculture,the average stable yield rate of M1S1 remained at98.7 % in 13 years,and there was no significant difference in yield components.However,M2S1 and M2S2 showed different degrees of yield reduction in 23 years,grain yield decreased decreased by 11.9 %-18.5 % and 7.1 %-16.3 %,respectively.In 2021-2022,except for 100-grain weight,which increased by 2.0 %-3.0 % and 2.2 %-3.4 %,the number of rows per ear and the number of grains per row decreased by 2.0 %-5.1 %,respectively.0.1 %-5.1 % and 3.3 %-12.9 %,3.8 %-10.3 %.(2)Intercropping treatment significantly(p < 0.05)increased canopy light interception(LI)compared with monocropping treatment.In the two-year experiment,the light interception of M1S1,M2S1 and M2S2 in the whole growth period increased significantly(p < 0.05)by 4.1 %-10.6 %,17.0 %-18.0 % and 19.0 %-29.9 %,respectively.The light interception of intercropping increased with the increase of the width of the small black bean,and also changed the light interception structure of the two crops in the intercropping population.The average light interception ratios of maize and small black beans in M2S1 and M2S2 were 84.4 % : 15.6 %,81.7 % : 18.3 % and 70.2 % : 29.8 %,respectively,indicating that more light energy was used by small black beans as the small black bean band widened.(3)The change of canopy structure of intercropping population significantly(p < 0.05)affected the net photosynthetic rate(Pn)of crops.The wide-narrow row planting structure constructed by intercropping showed obvious photosynthetic advantages for M2S1 and M2S2 wide-row crops.The net photosynthetic rates of M2S1 and M2S2 wide-row maize were significantly(p < 0.05)increased by 5.6 % and 19.7 %,respectively,compared with CKM.The net photosynthetic rate of small black beans also showed M2S2 > M2S1 > M1S1,but the net photosynthetic rates of M2S1 and M2S2 narrow-row maize were significantly(p< 0.05)lower than CKM.(4)Different intercropping patterns changed the root distribution of intercropping population,increased root length compared with CKM,and affected soil available nitrogen,available phosphorus and water content.The soil available nutrient content of M1S1 intercropping belt type was significantly higher than that of CKM(p < 0.05).Intercropping with small black beans significantly(p < 0.05)reduced soil water content compared with monocropping maize,and intercropping small black beans mainly utilized surface soil moisture.(5)The changes of intercropping canopy and soil physical and chemical properties affected the process of maize plant morphogenesis in different degrees.Compared with CKM,the plant height,stem diameter,leaf area and dry matter accumulation of M1S1 increased slowly in the early growth stage,but there was no significant difference in the later growth stage(p < 0.05).However,the growth rate of M2S1 and M2S2 was significantly(p < 0.05)increased in the early stage and significantly(p < 0.05)inhibited in the later stage.The whole plant dry matter accumulation of M2S1 and M2S2 maize was13.6 % and 21.9 % lower than that of CKM(p < 0.05).(6)Intercropping of maize and small black bean can significantly(p < 0.05)improve the nutrient return of the system.The dry matter and nutrient of intercropping green manure small black bean were significantly(p < 0.05)higher than that of monoculture maize.The average dry matter of M1S1,M2S1 and M2S2 was significantly higher than that of CKM by 50.2 %,10.3 % and 9.7 %,respectively(p < 0.05).The average total nitrogen and total phosphorus were significantly higher than CKM by 182.9 %,64.1 % and 77.8 % and 223 %,75.6 % and 102.0 %,respectively(p < 0.05).The maize yield,soil moisture and nutrients,population light interception and subsequent effects were comprehensively considered.M1S1 intercropping can provide a scientific basis for stable yield and nitrogen reduction in wheat-maize rotation system under the premise of ensuring stable yield of maize. |
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