Study On The Nutrients Requirement Characteristics And Optimization Management Technology Of Yam

Chinese yam is an importantly economic crop with the homology of medicine and food.In recent years,the problem of soil ecological environment is becoming more and more serious due to the effects of irrational fertilization,successive planting and allelopathic potential,which seriously restricts the sustainable development of yam production.The present study was conducted in Lixian county and Qingyuan county,which were the main production regions of yam in Hebei province.The nutrients requirement characteristics of the four main varieties of yam,the effects of yam/leguminous intercropping and fertigation on changes of soil ecological environment and yam yield were investigated.The main results were summarized as follows:?1?At harvest,the fresh and dry biomass of Ziyao,Dahebaiyu,Bangyao and Xiaobaizui were all shown in the order of rhizome>leaf>bulbil>stem,and the accumulation amount of N,P₂O₅ and K₂O in all yam varieties were shown in the order of K₂O?N>P₂O₅,and underground part>aboveground part.The content of Ca and Mg in all yam varieties were shown in the order of leaf>stem>rhizome>bulbil.The accumulation amount of Mg was greater than that of Ca,and the accumulation amount of Ca and Mg in aboveground part were higher than those in underground part.The accumulation distribution of Fe and Mn in aboveground and underground showed similar trends with Ca and Mg,inversely,Cu and Zn accumulation in underground part were higher than those in aboveground part,and the accumulation amount of four microelements in tested four yam varieties were all shown Fe>Zn>Mn>Cu.?2?The yield and N,Mg,Fe,Cu and Zn accumulation of Dahebaiyu were the highest among the four yam varieties.which indicated that Dahebaiyu had higher use efficiencies of nutrients.The P₂O₅ and K₂O accumulation of Ziyao were the highest.The highest accumulation amount of Ca and Mn,and the higher physiological efficiency were found in Bangyao.?3?In terms of nutrients requirement,4.61 kg N,1.22 kg P₂O₅,5.40 kg K₂O,0.46 kg Ca,1.03 kg Mg,15.51 g Fe,4.39 g Mn,1.55 g Cu and 5.96 g Zn were required for producing 1000 kg yam,respectively,and the ratio among N,P₂O₅,K₂O,Ca and Mg was 1:0.19-0.33:1.06-1.31:0.09-0.12:0.21-0.24.The ratio among Fe,Mn,Cu and Zn was 1:0.22-0.32:0.07-0.12:0.30-0.46.?4?Yam/alfalfa and yam/clover intercropping both increased the contents of nitrate nitrogen,available phosphorus and available potassium in 0-40cm soil layer,meanwhile reduced soil pH and electrical conductivity?EC?in early growth period and rhizome rapid expansion period of yam,and reduced the leaching of NO₃^--N in 0-100cm soil layer at yam harvest.Intercropping with leguminous crops increased the activities of urease,alkaline phosphatase,catalase and soil basal respiration in 0-40cm soil layer during the whole growth period of yam,but there was little influence on soil sucrase and dehydrogenase activities.Intercropping with leguminous crops could significantly increase comprehensive fertility index in 0-40cm soil layer,and improve the yam fresh and dry biomass of aboveground parts.?5?The results of fertigation experiment showed that,compared with farmers'fertilization practice,reducing top dressing fertilizer by 11.8%N,74.4%P₂O₅ and 50.2%K₂O had not significantly effect on yam yield.The application of humic acid could increased yam yield by 2.0-4.50 t/hm²,and increased economic benefit by 0.25-0.35 ten thousands yuan/hm².In summary,the nutrient management in production of yam should be based on biological characteristics and nutrients requirement characteristics of yam varieties.Fertigation and intercropping with leguminous crop could effectively save fertilizer rate,improve fertilizer efficiency and soil fertility.However,the nutrient comprehensive management technology under the new intercropping system is still to be studied.