| This study aimed to further optimize the northwest semi-arid areas of spring corn planting patterns by investigating the effects of three planting densities(L:52,500 plants ha-1;M:75,000 plants ha-1;H:97,500 plants ha-1)and three kinds of supplemental irrigation modes?RN:rainwater-harvesting planting with no-irrigation;RI:rainwater-harvesting planting with irrigation;CI:check irrigation?.Through field experiments in two consecutive years the effects of planting density and different supplementary irrigation methods on farmland soil moisture,maize growth,grain yield and water use efficiency were analysed.The main results are described herein.?1?RN and RI compared with CI in seedling significantly increased 40-60 cm soil water content and at trumpeting stage significantly increased 60-80 cm soil water content in In the two-year experiment.Before sowing soil moisture better and more precipitation in April in2016.before irrigation RN and RI can significantly improve the soil water storage at seedling stage and trumpet stage 0-200 cm soil layer compared with CI.The accumulation of soil moisture in late 2016 led to higher soil water storage in RI and CI treatments at the seedling stage and trumpeting stage in 2017 compared with RN.after irrigation at trumpeting stage RI treatment mainly by adding 40-100 cm soil water content and significantly improved the soil water storage in tasseling stage compared with the RN.The soil water storage capacity in the tassel phase of CI is higher than that of RI and RN because of CI's twice the amount of water than RI.Compared with RN,CI significantly increased soil moisture in lower layer?120-160cm?.At the grain filling stage and mature stage RI mainly by adding 0-120 cm soil water content to improve soil water storage especially in August more rain in 2017 the effect is more obvious.CI due to poor handling storing rainwater in reduced soil water storage compared to RI at mature stage.In the same supplementary irrigation mode after corn tasseling,the soil water storage decreases with the increase of planting density.The high-density treatment of the lower?120-160 cm?soil water deficit is more severe than low density.?2?The average water consumption of RI and CI treatments increased by 16.0%and20.8%respectively at low density 10.1%and 18.2%at medium density and increased by17.8%and 21.7%respectively at high density compared to RN.This shows that irrigation treatment less irrigation can significantly increase water consumption in the treatment of CI is higher than RI.In the medium and high density planting two-year average water consumption were increased by 8%and 4.3%compared to low density treatment under the treatment of RN,increased by 2.6%and 6.0%under the treatment of RI and increased by 5.7%and 5.2%under the treatment of CI.This shows that medium and high density planting of farmland increased water consumption compared to the low density.?3?The results of the two-year experiment showed that under the same planting density the plant height,leaf area index,and dry matter difference at the seedling and jointing stages of corn were relatively small.During the grain filling period,the two-year average plant heights of RI and CI treatments increased by 10.8%and 3.0%respectively compared to RN in 2016 and increased by 31.1%and 25.3%in 2017.The leaf area index of RI and CI treatment increased by 19.8%and 4.6%respectively compared to RN in 2016 and increased by 23.5%and 11.1%in 2017.During corn maturation period,dry matter under RI and CI treatment increased by 17.4%and 15.1%in 2016 compared to RN and increased by 60.1%and 50.0%in 2017 respectively.RI is more conducive to the accumulation of dry matter than CI and the effect is more pronounced in 2017 with poor soil moisture conditions.?4?At the same planting density,RI and CI significantly increased the grain weight and grain number per hectare compared to RN thereby increasing grain yield.The average grain yields of RI and CI treatments were 16.2%and 10.4%higher than those of RN in 2016 and5.7 and 4.7 times respectively in 2017.RI is more conducive to increasing grain yield than CI,and the effect is even more pronounced in 2017 when precipitation is poor before sowing and precipitation is less in July.Two years in the RI and CI modes,the medium-density processed grain yield is higher than the low density and high density.Average grain yields at low and medium densities increased by 10.4%and 16.2%,respectively,compared to high densities in two years.Among all the treatments the highest grain yield(9503.5 kg ha-1)was obtained with MCI treatment followed by MRI treatment(9438.1 kg ha-1).?5?At the same planting density for two years,the RI and CI treatments significantly increase the efficiency of precipitation utilization compared to RN and RI significantly improved irrigation efficiency?IWUE?compared with CI.Under different planting densities,the water use efficiency?WUE?of different supplemental irrigation methods showed some differences.In 2016 the WUE of RN and RI treatment was higher than CI at low density and high density especially at high densities difference is significant while the WUE processed by RI and CI at medium density is higher than RN.At the same planting density in 2017,RI and CI significantly increased WUE compared to RN.The two-year data shows that compared with RN average WUE processed by RI and CI increased by 70.6%and 45.7%respectively and RI-treated IWUE increased by 119.8%compared with CI.The effect of RI processing to improve WUE and IWUE is significantly better than that of CI.Studies have shown that two-year average WUE and IWUE under medium density planting are higher than high density.In all treatments M-RI obtained the highest WUE(30.7 kg ha-1 mm-1)and IWUE(25.2 kg ha-1 m-3).In summary rainfall irrigation combined with medium-density planting can improve soil moisture status,promote corn growth and increase grain yield.Under the medium density planting,although the check irrigation treatment obtained the highest grain yield,there was no significant difference between irrigation and irrigation,and the highest WUE and IWUE were obtained under the supplemental Rainfall irrigation.RI treatment obtained the highest net income(10689 yuan ha-1).rainfall irrigation combined with medium-density planting is a suitable planting model for effectively increasing the yield and water use efficiency of maize in the semi-arid region of northwest China. |
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