| The southern region of Ningxia is a typical rain-fed agricultural area,where limited and uneven spatial and temporal distribution of precipitation is a typical climatic characteristic,and the use efficiency of resources and crop yield can be improved by adopting rain-collection planting in agricultural production in this region.In order to further optimize the rainfed planting technology and to investigate the effects of changing the monopoly furrow ratio and planting density of rainfed planting on dry matter and nitrogen accumulation in spring maize,a two-factor randomized group trial of monopoly furrow ratio and planting density was set up in Pengyang,Ningxia,from 2020 to 2021,and a positioning study was carried out for two consecutive years.The two ratios were 80 cm:40 cm（R8F4）and 50 cm:10 cm（R5F1）,respectively,with the current 60 cm:60 cm（CK）as the control;three planting densities of67,500 plants/ha（L）,82,500 plants/ha（M）and 97,500 plants/ha（H）were set for each rainfed cropping pattern.（H）.The main results of the study are as follows:（1）The planting structure of wide and narrow rows caused by different monopoly ratios influenced the population structure and photosynthetic characteristics of maize.In vertical space,plant height increased with increasing monopoly furrow ratio at the same density,shown as R5F1>R8F4>CK;at the same monopoly furrow ratio,plant height decreased with increasing density.Horizontally,the leaf area index increases with increasing monopoly ratio and planting density.The light transmission rate at the bottom of the canopy showed a negative correlation with planting density at the same monopoly furrow ratio,gradually decreasing with increasing planting density.Photosynthetic rate was positively correlated with monopoly furrow ratio,and in 2020,the photosynthetic rate of R5F1 was significantly greater than that of CK at all planting densities,increasing by 30%,24%and 25%at L,M and H densities respectively.In 2021,the net photosynthetic rate of R5F1 and R8F4 was greater than that of the control treatment CK at all densities,but the differences between treatments were not significant,and the photosynthetic rate of R5F1 was 7%,16%and 13%higher than that of CK at L,M and H densities,respectively.（2）Both changing the monopoly furrow ratio and increasing planting density affected dry matter accumulation in maize.At the same monopoly ratio,the dry matter mass of the plant population increased and then decreased with increasing density,and was greatest at M.In2020,at M density,the dry matter mass at maturity was significantly higher by 17.0%（P<0.05）for R5F1 compared to CK,and the difference between R8F4 and the other two monopoly ratios was not significant,but increased by 8.8%compared to CK;in 2021,at M density,the dry matter mass at maturity was significantly higher by 10.9%（P<0.05）for R5F1 compared to CK,and by 2.8%for R8F4 compared to CK.R5F1 had a significant 10.9%（P<0.05）higher dry matter mass than CK and R8F4 had a 2.7%increase over CK.At maturity,the population dry matter accumulation of leaves,stalks,seeds,rachis and bracts of maize plants all increased gradually with the increase of the monopoly ratio at the same planting density;at the same monopoly ratio,the population dry matter mass of leaves and stalks increased with the increase of density,while the population dry matter mass of bracts decreased with the increase of density,and the population dry matter of seeds and rachis increased first and then decreased with the increase of density.（3）The accumulation of dry matter is essential for the formation of grain yield,and increasing the monopoly to furrow ratio can increase grain yield.Compared with CK,seed yield of R5F1 was significantly higher by 13.2%,14.3%and 9%in 2020 and 27.6%,28.6%and 23.9%in 2021 at L,M and H densities,respectively（P<0.05）.Comparing the two-year trials,the maximum seed yield was achieved at M density R5F1,with a maximum of 12026.0 kg·ha-1.（4）The uptake and accumulation of nitrogen in the above-ground part of the plant is closely related to dry matter accumulation.At the same monopoly ratio,the total nitrogen accumulation of maize plants became larger and then decreased with increasing density,with the maximum at M density.At the same density,increasing the proportion of monopoly furrows could significantly increase the nitrogen accumulation of maize plants at maturity.Compared with CK,the nitrogen accumulation of R5F1 at M density was significantly higher by 19.1%in 2020;and by 9.2%in 2021.In summary,on the basis of the rainfall harvesting system,compared to traditional monopoly furrow cropping,setting the monopoly furrow ratio to R5F1 under M planting density conditions optimises the canopy structure of the maize population,promotes the growth and development of maize,improves the formation of photosynthetic products and the accumulation of nitrogen in maize,and achieves the highest maize seed yield. |
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