| Due to the scarcity of freshwater resources in arid and semi-arid regions of China,the inefficient utilization of water and fertilizer resources in saline-alkali land,and the unreasonable status of secondary salinization of soils caused by irrigation and nitrogen application,The field irrigation experiment was conducted in the Saline-alkali Improvement Experimental Demonstration Base in Huairen County,Shuozhou City,Shanxi Province from 2016 to 2017.To study the distribution patterns of soil water and nitrogen,water consumption characteristics of silage maize,water and nitrogen use efficiency,crop growth indicators and yield changes under different water and nitrogen levels and different tillage patterns.Finally,it proposes a suitable local water and fertilizer production model,which is of great significance for increasing the local water use efficiency,reducing the amount of fertilizer and increasing the yield of corn.The experiment selected a typical saline-alkali land in Datong Basin,with silage corn and oats as the research objects,and the oat potted experiment controlled the two factors of water and nitrogen.The water factors were high water W1(irrigation quota 140mm)and low water W2(irrigation quota 100mm).Nitrogen supply levels were N90(90 kg/hm2),N60(60 kg/hm2),N30(30 kg/hm2),N10(10 kg/hm2),and no nitrogen application N0.The silage corn field experiment was based on three factors:water,nitrogen and tillage methods.The farming methods were full-membrane double-furrow sowing,full-film flat(QP),and uncovered flat(P);the water was set in two treatments,and the upper limits of irrigation were respectively For the field water holding rate of 90%(W1)and field water holding capacity of 80%(W2),the irrigation lower limit is 55%-65%of the field water holding rate,and the nitrogen application amount is set to N1(270kg/hm~2)and N2(225kg/hm~2),N3(315kg/hm~2)was added in 2017,and a total of 18 treatments were performed,and each treatment was repeated in 3groups.The research conclusions mainly include the following solutions:(1)Oat pot trials showed that reasonable water and nitrogen measures can effectively reduce the salt accumulation during the growth period of oats,reduce the salt stress during the growth period,and effectively reduce the loss of nitrogen and slow down the migration of nitrate nitrogen into the soil.Among them,the soil conductivity of W1N10 and W1N60 treatments decreased by 7.91%and 5.72%,respectively,compared with the emergence period in the mature stage.When the nitrogen application rate was kept at 10~30 kg/hm~2,the irrigation volume was reduced from 140 mm to 100 mm,and the fresh and dry oat yields did not decrease significantly.The amount of nitrogen applied and the amount of water applied to oat production and yield components had no significant effect.Taking into account the dual effects of water and nitrogen,the water-saving and nitrogen-reducing W2N30 treatment scheme is the best,the potential risk to the environment is small,and the investment in water and fertilizer is also saved.(2)Find out the water and salt migration of maize soil by studying the different water and nitrogen combinations and tillage methods:Soil electrical conductivity has obvious stratification in 0-100cm soil layer,soil electrical conductivity in 0-40cm soil layer is significantly higher than that in 40-100cm soil layer,and the closer to the surface layer,the greater the electrical conductivity.Under the same irrigation conditions,the greater the amount of nitrogen applied,the higher the surface conductivity of the soil and the more salt accumulation;Under the same nitrogen application rate,adding a certain amount of irrigation can significantly reduce the surface salt content in the soil,but sufficient irrigation can not effectively reduce the surface salt content of the soil.Compared with the W1 treatment,the surface conductivity of the soil only decreased by 3.7%.Under the same conditions of water and nitrogen,the full-film double-furrow sowing has more advantages than the full-film flat and uncoated flat,which has obvious advantages in reducing the surface salt and water retention.Among them,W1N1 treated with full-film double-furrow furrow sowing had a 57.4%lower electrical conductivity than QP-W1N1,and it could be ensured that the water content in the root zone of silage maize was maintained at the three irrigation levels(W-fill,W1,and W2).The amount of water is 60%~80%.(3)The application of nitrogen fertilizer can significantly increase the content of nitrate nitrogen in soil(p<0.05);with the increase of irrigation volume,the nitrate nitrogen in soil has a decreasing trend.Under the W1 level,the first peak of nitrate nitrogen content appeared at 20-40cm in the seedling stage in 2016,among which,the nitrate nitrogen content of W1N2 treatment was the highest,reaching 34.33mg/kg.With the progress of growth period and the increase of irrigation times,the soil layer with the peak soil nitrate nitrogen significantly decreased.Among them,the peak of nitrate nitrogen in W-charged N1 soil appeared in the 80-100cm soil layer and reached 100cm.There is also no significant downward trend in the soil layer,which seriously threatens the safety of groundwater.Ammonium nitrogen which migrated less with water is mostly concentrated in 0-20cm soil layer.Under the same irrigation condition,the ammonium nitrogen in the surface soil was less.The ammonium nitrogen content of W1N2 treatment reached 16.62mg/kg in the emergence period.Under the same nitrogen application condition,increasing the amount of irrigation can significantly reduce the content of ammonium nitrogen in the soil during the big bell-mouthing period.Among them,the ammonium nitrogen content in the0-10cm soil layer treated with W1N1 is 78%lower than that of the W2N1treatment.Full-film double-furrow planting can significantly increase the ability of absorbing ammonium nitrogen during the early growth period of maize.Among them,there is a significant difference in the content of ammonium nitrogen in the 0-20 cm soil layer between the maize emergence stage and the big bell-mouth stage under the same water and nitrogen conditions.Ammonium nitrogen content showed full-film flat>non-coated flat>full-film double-furrow sowing.(4)Appropriate nitrogen application rate and irrigation amount can increase corn yield and promote corn growth.Especially when maize is subject to water and soil salt stress,increase irrigation amount and nitrogen application rate,and change farming methods,can promote corn growth.However,adequate irrigation has little effect on LAI and yield increase of maize.Non-irrigated irrigation will not significantly reduce LAI.Among them,W1N1 treatment was only 2.2%lower than corn LAI treated with W-N1 in 2016 corn maturity.The water use efficiency of crops is mainly affected by the amount of irrigation water and different farming modes.To a certain extent,the amount of irrigation water can increase the water use efficiency,but when the irrigation water is excessive,the water use efficiency will decrease.The amount of nitrogen applied was the main factor affecting the agronomic efficiency of nitrogen fertilizer and partial productivity of nitrogen fertilizer.Water had little effect on nitrogen fertilizer agronomic efficiency and nitrogen partial productivity.Among them,the nitrogen fertilizer utilization rate under W-N1 treatment in 2016 was only 2.9%higher than that of W1N1.In summary,the local corn planting should adopt the full-film double ridge cultivation method,water and nitrogen systems use water conservation 90%,nitrogen application amount 225-270kg/hm~2. |
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