| Reasonable planting density and nitrogen application rate are critical to high yield and high efficiency of maize.Strip intercropping is a new maize planting mode developed in Sichuan and even Southwest China in recent 20 years.Reasonable planting density and nitrogen application rate are the key to high yield and high efficiency of maize.The experiment was carried out in three typical zonal intercropping maize producing areas in Sichuan in 2018(South Sichuan-Renshou,Central Sichuan-Lezhi,Northeast Sichuan-Pingchang).Three planting densities,A1:45,000 plants/hm~2(farmer's planting density),A2:60,000 plants/hm~2(increasing 15,000 plants/hm~2),A3:75,000 plants/hm~2(increasing 30,000 plants/hm~2),and three nitrogen application levels,B1:180 kg/hm~2(reducing nitrogen 90 kg/hm~2),B2:225 kg/hm~2(reducing nitrogen 45 kg/hm~2),B3:270kg/hm~2(increasing nitrogen application rate),were designed.The effects of dense fertilizer on population yield,material accumulation,lodging rate and resource utilization efficiency of strip intercropping maize were analyzed in order to provide production guidance for popularizing densification and nitrogen reduction technology of strip intercropping maize in Sichuan area in the future.The main results are as follows:1.Effects of Densification and Nitrogen Reduction on Maize Yield and Resource Utilization in Intercropping SystemThe maize yield of A2 and A3 increased by 16.44%and 19.26%on average compared with A1.Significant differences were observed among three locztions,A2B2 and A3B3 at Lezhi and Renshou,and A3B2 at Pingchang,respectively,were significantly increased by20.85%compared with A1B3.The resource utilization efficiency of three experimental locations were 26.32%higher than A1B3,The utilization efficiency of post-flower resources was significantly improved by 26.29%.The results showed that densification and nitrogen reduction technology could improve the utilization efficiency of resources,especially post-anthesis resources,give full play to the potential of population yield,realize the balance between supply and demand,and achieve the goal of increasing yield of intercropping system.The maximum resource utilization efficiency of each test point is quite different,the maximum RUE of Renshou test point is 25.86%and 17.11%higher than that of Lezhi,Pingchang test point,the maximum WUE of Pingchang test point is37.91%and 22.24%higher than that of Renshou and Lezhi,and the maximum HUE difference is no significant.2.Effect of Densification and Nitrogen Reduction on Lodging of MaizeWhen the planting density increased to medium density,there was no significant difference in maize lodging rate.When the planting density was further increased,the maize lodging rate was significantly increased by 4.96%.With the decrease of nitrogen application rate,the lodging rate of maize reached the lowest under medium nitrogen,which was 1.53%lower than that of high nitrogen.Nitrogen application could regulate maize lodging caused by increasing density.Comparing with the lodging rate of B3treatment,the lodging rate of Renshou and Lezhi treatment of B1 and B2 decreased by1.67%and 3.06%respectively,under high density,the lodging rate of medium and high nitrogen application rates in Renshou test site had no difference,and the lodging rate of low nitrogen increased by 1.55%.The lodging rate of B2 treatment in Lezhi and Pingchang was the lowest,which was 6.01%lower than that of B3 treatment on average.3.Effect of Densification and Nitrogen Reduction on Maize Production CapacityThe dry matter accumulation under A2 and A3 increased by 16.32%and 22.23% on average.There was no significant difference in total dry matter accumulation between B2 and B3 levels,and the average decrease in B1 was 6.10%.The maximum leaf area index(LAI)of Renshou and Lezhi experimental sites increased significantly under A2B2and A3B3.Compared with A1B3,the LAI increased by 39.40%on average,and the leaf senescence rate decreased.The dry matter assimilation increased by 20.83%after anthesis,and the total dry matter accumulation increased by 20.69%.In Pingchang,the maximum leaf area index(LAI)of A3B2 was higher than that of other treatments,which increased by45.73%compared with A1B3,and increased the dry matter assimilation and total dry matter accumulation after anthesis by 29.12%and 29.71%,respectively.The results showed that increased density and decreased nitrogen could increase the area of maize under light,increase the utilization rate of light energy,facilitate the accumulation and redistribution of dry matter,and provide material basis for high yield.4.Effects of Densification and Nitrogen Reduction on Nitrogen Accumulation in MaizeTotal nitrogen accumulation increased by 10.70%,14.48%under A2 and A3 with increasing density.The total nitrogen accumulation of B1 and B2 was 7.27%,1.19%lower than that of B3.The total nitrogen accumulation under A2B2 and A3B3 in Renshou and Lezhi experimental locations increased by 9.98%and 19.41%respectively,and the total nitrogen accumulation and pre-anthesis nitrogen transport of maize under A3B3 were15.87%,15.24%respectively,and 20.61%respectively.The pre-anthesis nitrogen transport and post-anthesis nitrogen accumulation of A3B2 in Pingchang location were19.62%?20.99%and 20.51%higher than those of A1B3.Increasing planting density and reducing nitrogen application properly are conducive to nitrogen accumulation and distribution to grain after anthesis.It is also conducive to meeting the needs of vegetative organs and laying a foundation for further increasing yield.In summary,the application of 225kg/hm~2 nitrogen at 60,000 plants/hm~2 and225kg/hm~2 nitrogen at 75,000 plants/hm~2 in Renshou and Lezhi can ensure high and stable yields of maize in the system,reduce planting costs to the greatest extent and increase farmers'income. |
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