Effects Of Humic Acid And Nitrogen On Yield And Quality Formation Of Edible Sweet Potato

This experiment was carried out at the experimental station of Shandong Agricultural University from June 2007 to October 2008. The forming rule of yield and quality of different treatment of humic acid on sweet potato and the effects of activation of different amount of humic acid and nitrogen levels on sweet potato have been studied in micro-regional of the daejeon.The main results were as follows:1 The effect of different treatment of humic acid on yield and quality formation of edible sweet potato1.1 The effect of different treatment of humic acid on yield and quality of root tuberComparing with non- activated humic acid treatment, the yield of activated humic acid treatment is similar. Acid-activated humic acid treatment significantly increased soluble sugar, vitamin C and starch content, and a significant reduction in nitrate content.1.2 The effect of different treatment of humic acid on the plants of absorbing nutrients and mineral elements content of soil Comparing with non- activated humic acid treatment, activated humic acid treatment promote the plants to absorb elements,these elements include N, P, K, Ca, Mg, S, B, Mn, Cu, Fe and Zn. In the harvest period, activated humic acid treatment significantly increased the element of P,K,Mg,S content in the soil and the other elements content in the soil is similar.2 The effect of different amount of humic acid and two different nitrogen levels on yield and quality formation of edible sweet potato2.1 The effect of different amount of humic acid and two different nitrogen levels on yield and quality of root tuber Under the conditions of non-application of nitrogen fertilizer, comparing with non-application of acid-activated humic acid treatment, AHA1(application of humic acid for the activation of 45 g/m2)treatment significantly increased yield by 7.2% and AHA2(application of humic acid for the activation of 90 g/m2) treatment increased yield by 2.2%.Under the conditions of the N180 kg/hm2, comparing with non-application of activated humic acid treatment, AHA1(application of humic acid for the activation of 45 g/m2)treatment and AHA2(application of humic acid for the activation of 90 g/m2) treatment respectively increased yield by12.9% and 5.8%. Comparing with non-application of nitrogen fertilizer, the yield of N180 kg/hm2 treatment significantly increased.Under the same nitrogen levels, comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased soluble sugar, crude protein and vitamin C content and there are not different in starch content . AHA1 treatment significant reduced in nitrate content. AHA2 treatment is similar in nitrate content.Under the conditions of non-application of activated humic acid,comparing with non-application of nitrogen fertilizer, theN180 kg/hm2 treatment significantly reduced soluble sugar, crude protein and vitamin C content,significantly increased nitrate content and there are not different in starch content in root tuber.2.2 The effect of different amount of humic acid and two different nitrogen levels on Carbohydrate accumulation of edible sweet potato Under the conditions of non-application of nitrogen fertilizer, there are significantly differences in all treatments throughout the growth period. In the harvest period,comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased dry matter per plant accumulation by 34.6% and 27.4%. Under the conditions of the N180 kg/hm2, there are no differences in all treatments in the early stage of growth and significantly differences in the mid-and late stage. AHA1 treatment was maximum accumulation of dry matter per plant and AHA0 treatment was minimum accumulation of dry matter per plant .The rule of root dry matter accumulation is similar to dry matter per plant accumulation.Under the same nitrogen levels, in the harvest period, comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased soluble sugar content. AHA2 treatment was the highest soluble sugar content in the leaves; AHA1 treatment was the highest soluble sugar content in the stalks and stems.Under the conditions of non-application of nitrogen fertilizer, comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased soluble sugar content in the root tuber by 15.4%, 11.7%. Under the conditions of the N180 kg/hm2, comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased soluble sugar content in the root tuber by 17.3%,9.3%.The main reason for different amount of humic acid treatment increased soluble sugar content in the root tuber is that different amount of humic acid treatment increased sucrose,fructan, glucose, fructose content and appropriate application of activated humic acid treatment enhanced better.Under the conditions of non-application of nitrogen fertilizer, AHA0 treatment was the highest starch content and AHA1 treatment was the lowest starch content in the leaves; AHA1 treatment was the highest starch content and AHA2 treatment was the lowest starch content in the stalks and stems.Under the conditions of the N180 kg/hm2, AHA1 treatment was the highest starch content and AHA0 treatment was the lowest starch content in the stalks and leaves; AHA2 treatment was the highest starch content and AHA0 treatment was the lowest starch content in the stems; the starch content in root tuber is smiliar.2.3 The effect of different amount of humic acid and two different nitrogen levels on the plants of absorbing nutrients and mineral elements content of soilUnder the same nitrogen levels, comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly promote the plants to absorb elements. With the increase in the amount of humic acid, the growth rate of absorption reduced. Comparing with non-application of nitrogen fertilizer, N180 kg/hm2 treatment significantly increased the absorption of Ca,Mg,S,Mn and reduced the absorption of P.Under the conditions of non-application of nitrogen fertilizer, in the post-harvest, comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased P,K,Zn,Ca,Mg and Mn content in the soil, AHA1 treatment was the highest P,K and Zn content in the soil; AHA2 treatment was the highest Ca,Mg and Mn content in the soil;N,B,S,Fe and Cu content in the soil were similar.under the conditions of N180 kg/hm2, Comparing with non-application of activated humic acid treatment, AHA1 treatment and AHA2 treatment significantly increased N,P ,K,Ca,Mg,B,Fe,Cu,Zn,S and Mn content in the soil, AHA2 treatment was the highest N,K,Ca,Mg,B,Fe,Cu and Zn content and AHA1treatment was the highest P,S and Mn content in the soil.