Effect Of Nitrogen And Potassium Interaction On Nutrient Absorption, Utilization, And Yield Of Sweet Potato

In order to research the effect of nitrogen and potassium interaction on nutrient absorption, utilization, and yield of sweet potato, we used ‘Jixu23’ sweet potato starch cultivar as the test material. The split plot experiments with 3 nitrogen treatments( No nitrogen treatment,medium nitrogen treatment,high nitrogen treatment) and three potassium treatments(No potassium treatment,medium potassium treatment,high potassium treatment), including 9 combinations of N and K treatments, were designed.The study was carried out in Agronomy Experimental Station of Shandong Agricultural University. The main results were as follows: 1. Yield and its composing factors of sweet potatoNitrogen fertilizer can decrease the number of sweet potato per plant; increase the weight of sweet potato per plant instead. Potassium fertilizer can increase the number and the weight of sweet potato per plant. Under the condition of no nitrogen fertilizer, the application of 18 g/m2 of potash production is higher;Under the condition of 9 g/m2 nitrogen fertilizer, the application of 36 g/m2 of potash production is higher;Under the condition of 18 g/m2 nitrogen fertilizer, though the application of 36 g/m2 of potash production high, it is lower than the no nitrogen and 9 g/m2 nitrogen one. Therefore, under the condition of nitrogen fertilizer, it needs more potash fertilizer to obtain high yield, even under the high nitrogen fertilizer, much more potassium can’t get high yield of sweet potato. 2. Dry matter accumulation and distributionAt early stage of storage root thickening, appropriate rate of nitrogen could promote the out ground part’s growth; increase the branch number, the longest stem length and basal stem diameter; increase the starch in stem and storage root. However, excessive nitrogen fertilizer can decrease the leaf number, the branch number, the longest stem length and the basal stem diameter at the early stage of storage root thickening, increase the chlorophyll content and chlorophyll a/b values, but it no significant effect on photosynthetic rate. Appropriate rate of nitrogen also could increase leaf stomatal conductance and intercellular CO2 concentration, raise photosynthetic rate of leaves; increase the max dry matter accumulation rate and ahead the time of the max dry matter accumulation rate of storage root. However, excessive nitrogen fertilizer can decrease the max dry matter accumulation rate, push the time of the max dry matter accumulation rate, and decrease the mean dry matter accumulation of sweet potato.Potassium fertilizer can increase the leaf number and the longest stem length, promote the photosynthetic rate at the early storage root thickening, promote the out ground part growth and photosynthetic accumulation. Besides, potassium can decrease sucrose content in storage root at the mid storage root thickening, increase starch accumulation in leaves and decrease the starch in petiole at the late storage root thickening; increase the max dry matter accumulation rate, ahead the time of the max dry matter accumulation rate of storage root, increase the thickening rate and dry weight in storage root. But excessive potassium goes against the storage root thickening.Appropriate nitrogen and potassium contributes to improving the leaf number per plant, the longest stem length, especially to the basal stem diameter at early storage root thickening, and it can increase the branch number per plant. Besides, at early storage root thickening stage, appropriate nitrogen and potassium may increase specific leaf weight, chlorophyll a/b values, photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration, promote the photosynthetic substances accumulation finally. What’s more, it promote the initial dry matter accumulation, ahead the time of the max dry matter accumulation rate, promote starch accumulation in stem and storage root at late storage root thickening. Based on high nitrogen, no potassium or excessive potassium fertilizer may promote dry matter distributing more in out ground parts, lead to spindling, decrease harvest index. 3. Absorption and utilization of nitrogen and potassiumNitrogen fertilizer can promote nitrogen and potassium accumulation of different organs at early and late storage root thickening. And excessive nitrogen can decrease nitrogen absorption utilization efficiency(NRE) and nitrogen partial factor productivity(NPFP). Potassium fertilizer significantly influences K/N of different organs at different times, because it can decrease nitrogen accumulation in petiole, stem and storage root at early storage root thickening, but increase potassium accumulation in them. Based on no nitrogen and 9g/m2 nitrogen, KRE and KPFP is high at 18g/m2 level.