Mechanism Of High-Efficient Utilization Of Water And Fertilizers By Potato Under Drip Fertigation

Potato is the fourth largest food crop besides wheat,corn and rice in the world.It is one of the top ten popular nutrition and health foods,which is loved by people.The water and nutrients needed for crop growth can be directly transferred to the crop root area by drip fertigation technology,which is beneficial to improve the water and fertilizer utilization efficiency of the crop,and has the advantages of saving water and fertilizer,and convenient management.In this study,potato?purple white?was used as the experimental material at the Potato Experimental Station of Northwest A&F University of Yulin in Northern Shaanxi from 2016to 2019.In 2016-2017,three factors?drip irrigation frequency,drip irrigation volume and fertilization volume?were set.Each factor includes 3 levels and there were 27 treatments in total.The irrigation frequency included once every 4 days?D₄?,once every 8 days?D₈?and once every 10 days(D₁₀).The irrigation levels consisted of full irrigation?W₃:100%ETc,ETc is the crop evapotranspiration?,medium irrigation?W₂:80%ETc?and low irrigation?W₂:60%ETc?.The fertilizer?N-P₂O₅-K₂O?levels included low fertilization(F_1,100-40-150 kg ha^-1),medium fertilization(F₂,150-60-225 kg ha^-1)and high fertilization(F₃,200-80-300 kg ha^-1).In 2018-2019,a two-factor test of drip irrigation water and fertilization amounts was implemented under the condition of drip irrigation frequency of 8 days.Three levels of drip irrigation water were unchanged.But the amount of fertilization 0 kg/ha?F₀?and 250-100-375kg/ha?F₄?were added,there were a total of 15 treatments.Under the conditions of drip irrigation and fertilization,the effects of different modes of water supply and fertilizer on potato growth,physiology,yield,quality,water and fertilizer absorption and utilization,and the distribution of soil moisture and nutrients in the root zone were analyzed.The main results were shown as below:?1?The response of potato growth,yield,quality and water and fertilizer productivity to different irrigation frequency,irrigation amounts and fertilization rate under the condition of drip irrigation and fertilization was revealed.The plant height,leaf area index,dry matter,yield and its components,starch content,vitamin C content,irrigation water use efficiency and fertilizer partial factor productivity?PFP?of potato of the deficit irrigation treatments increased with the increase in irrigation frequency at the same fertilization level.But these indicators increased first and then decreased with the increase of irrigation frequency under the condition of full irrigation.When the irrigation frequency and fertilization amount were same,except for the irrigation water use efficiency,the other indicators increased with the increase of irrigation water.Under the same irrigation frequency and irrigation level,the tuber yield and IWUE increased as the fertilization level increased.However,the PFP decreased as the fertilizer rate increased.The starch content and vitamin C increased first and then decreased with the increase in the application rate of the fertilizer under full irrigation.The change in the content of reducing sugars was opposite to that of the starch.Using the TOPSIS method,we found that when the irrigation frequency was once every 8 days?D₈?,the irrigation amount was fully irrigated?1.0 ETc?with a high fertilizer?N-P₂O₅-K₂O?level(F₃,200-80-300 kg ha^-1),and the multi-target comprehensive level of potato was optimal.?2?The variation rules of potato leaf area index,dry matter accumulation,yield,quality and economic benefits under different drip irrigation levels were found.With the development of growth period,the leaf area index of potato changed in a single peak curve,the net assimilation rate?NAR?decreased exponentially and the dry matter accumulation changed in a S-shaped curve.The maximum rate of dry matter accumulation was 64.85-73.75 days after sowing in 2018,64.45-70.54 days after sowing in 2019.When the fertilization level was the same,the leaf area duration?LAD?,SPAD value and net income increased with the increase in irrigation levels.When the irrigation level was the same,net income increased with the increase in fertilizer levels.The starch content and vitamin C content of W₃F₂ were the highest in 2018 and 2019.Thee treatment of the maximum yield was W₃F_4,51740 kg/ha in 2018 and 51335 kg/ha in 2019,respectively,but under the condition of irrigation level W₃,there was no remarkable difference in the yield and its components,net income and SPAD value between fertilization levels F₃ and F₄.Through principal component analysis,the yield components and quality of potato were comprehensively evaluated,and it was found that the irrigation level of W₁had the worst quality,under the same irrigation levels,the quality of the fertilization of F₃ treatment was the best,and that of the fertilization of F₀ treatment was the worst.?3?The rules of nitrogen,phosphorus and potassium absorption,transport and utilization in potato under different drip irrigation levels were clarified.In the earlier growing period,nitrogen,phosphorus,and potassium were mainly accumulated in the leaves.With the development of growing period,the accumulated amount of absorption of N,P,and K showed a slow-fast-slow"S"curve growth variation trend,and the highest growth rate was about60-70 days after sowing;at harvest,nitrogen,phosphorus and potassium were mainly concentrated in tubers,the nitrogen content in tubers exceeds 60%,phosphorus exceeds 70%,and potassium exceeds 50%.The accumulation of nitrogen,phosphorus and potassium,fertilizer use efficiency?FUE?and fertilizer partial factor productivity?PFP?increased with the increase of irrigation amount.There was no significant difference in agronomic fertilizer use efficiency between treatments.Phosphorus use efficiency was significantly higher than nitrogen and potassium.Under the same irrigation level,with the increase of the amount of fertilization,the PFP decreased exponentially,while the FUE increased first and then decreased.There was a quadratic parabolic linear relationship between the FUE and the amount of fertilizer applied,and FUE was the largest when the fertilizer level was F₃.?4?The characteristics of soil nutrient transport in potato root zone under different drip irrigation levels were clarified.In the 0-100 cm soil layer,when the fertilization level was the same,the content of nitrate nitrogen,available phosphorus and available potassium decreased with the increase of irrigation amount due to loss and plant absorption.And at vertical depth,nitrate nitrogen,available phosphorus,and available potassium move downward with the increase of irrigation volume.When the irrigation level was the same,the accumulation of nitrate nitrogen,available phosphorus,and available potassium increased with the increase of the amount of fertilization.Compared with the no fertilization,the distribution of nitrate nitrogen,available phosphorus and available potassium at the fertilization level decreased with increasing horizontal distance,and the contents of nitrate nitrogen,available phosphorus and available potassium at 0 cm below the dripper were the highest.High-fertilizer treatment increased the risk of nutrient residue and loss while obtaining high yields,which was detrimental to environmental benefits.?5?The characteristics of water transport in potato root zone,as well as the changes of water consumption and water use efficiency under different drip irrigation levels were revealed.Soil moisture below 40 cm was generally lower than the upper layer.During the whole growth period of potato,at the soil layer of 50 cm and 70 cm,the soil water content of the low irrigation level W₁ changed less,but the soil water content of the irrigation level W₃changed more.The water content of each soil layer increased with the increase of irrigation water,and the water consumption was the fastest during tuber formation and swelling phase.The soil water content generally decrease D with the increase of fertilizer application.Under the same fertilization level,as the applied of irrigation increased,the water consumption became larger,but the irrigation water use efficiency decreased,and the water use efficiency increased first and then decreased.Under the same irrigation level,water consumption,water use efficiency and irrigation water use efficiency all increased with the increase of fertilizer application.Under the full irrigation level W₃,there was no significant difference in water use efficiency and irrigation water use efficiency between fertilization levels F₃ and F₄.The water-yield response coefficient k_y of ootato was 1.726.?6?The strategy of irrigation and fertilization with the best comprehensive benefits of potato high-yield,high-quality,high-efficiency and environmental protection in the sandstorm area in northern Shaanxi was proposed.Based on the combination of Analytic Hierarchy Process?AHP?and fuzzy comprehensive evaluation?FCE?method,the economic benefit,quality,water and fertilizer utilization efficiency and environmental benefit of potatoes in Yulin sandstorm area in northern Shaanxi were comprehensively evaluated.It was found that the treatment W₂F₄,W₃F₂,W₃F₃,W₃F₄ in the sandstorm area in northern Shaanxi all performed well.After further scoring and ranking,it was found that the best irrigation and fertilization combination for potato with high yield,high quality,high efficiency and environmental protection was the irrigation level of full irrigation W₃?100%ET_C?,and the amount of fertilizer?N-P₂O₅-K₂O?is F₃?200-80-300 kg/ha?.