Study On Effect Of Soil Potassium Levels On Potassium Accumulation, Distribution And Yield Of Soybean

Soybean is not only grain and oil crop but also the important nitrogen fixation crop in China. It’salso the main source of protein, feed and edible oil. Potassium is one of the necessary nutrients forgrowth of plant and doesn’t participate in the composition of the organic compounds, which is differentfrom nitrogen and phosphorus. Potassium mainly exists in the plant vacuoles and has the close relationwith the physiological metabolism, stress resistance and quality improvement of plants. Effects ofdifferent soil potassium levels on potassium uptake, accumulation, distribution of soybean organs andyield at different growth periods were researched. The suitable soil potassium levels of soybean werediscussed in order to broaden the ideas of soybean potassium research, which are profound implicationsfor scientific application of potash. This work was conducted to study systematically on the potassiumuptake, accumulation and distribution and yield of soybean with pot experiment and field experiment inthe experimental station of Northeast Agricultural University (NEAU) in2012.6soil potassium levelswere set in the pot experiment and the available potassium content were135.1,160.8,215.8,269.1,312.0and389.3mg/kg respectively.3potassium sulfate fertilizer levels were set in the field experimentand the fertilizer application amounts were0,150and300kg/hm2respectively. Results were shown asfollows：（1）Potassium contents of soybean organs were different at each growth periods. K content ofvegetative organs was the highest at seedling period and it showed a decreasing tendency during thewhole growth period, pods’ showed the same tendency. In the beginning period of soybean growth,petiole and stem’s K contents were higher than leaf and root’s. From seed filling period to mature period,K content of pod was obvious higher than other organs. K contents of the upper vegetative organs werehigher than the lower vegetative organs and K content in each part of pod didn’t have many differencesduring the whole growth period（.2）Soil potassium levels affected K content of soybean plant. With soilpotassium level rising, K content of each organ increased, and petiole and stem’s K content changedobviously at different potassium levels. The soil potassium levels had great influence on K content ofplant when the available potassium content in soil was low（135.1mg/kg~215.8mg/kg），and K contentof plant would not be changed obviously when the available potassium content in soil was high（269.1mg/kg~389.3mg/kg）. K content of pod didn’t change almost at the high soil potassium levelduring the later period（.3）Potassium accumulation center changed as the soybean grew. Potassium wastransferred to the organs with the active physiology and metabolism during the whole growth period. At the beginning period of soybean growth, leaf was the K accumulation center and root followed. Fromfull-blossom period to multi-pod period, K accumulation of leaf remained the highest and stem’s Kaccumulation improved obviously at the same time. During the later period, reproductive growthbecame the main stage of soybean and potassium was transferred to the pod which had become the Kaccumulation center at that time. During the mature period, the majority of potassium was accumulatedin seed and K accumulations of leaf, petiole, stem and root decreased to the lowest.（4）Potassiumaccumulation and distribution were different during the whole growth period. The percentage of leaf Kaccumulation of plant K accumulation decreased gradually as soybean grew. From early-blossom periodto full-blossom period, K accumulation of the upper leaf and petiole was higher than the middle andlower parts and lower stem’s K accumulation was higher too. At the beginning of multi-pod period, Kaccumulations of upper and middle organs were higher than the lower parts. During the later period,potassium was transferred from vegetative organs to pod and most potassium was distributed to theupper and middle pods.（5）Potassium accumulations of soybean were different at different soilpotassium levels. In the low available potassium content soil （135.1mg/kg~215.8mg/kg）, Kaccumulation of each organ increased with the rising of soil potassium level and K accumulation of podshell and seed increased obviously at the soil potassium level of215.8mg/kg during the later period. Inthe high available potassium content soil（269.1mg/kg~389.3mg/kg）, K accumulation of soybeandidn’t change obviously even if the soil potassium level continued to be increased. At the soil potassiumlevel of312mg/kg, K accumulation of seed would not change with level of soil potassium increasing.From early-blossom period to seed filling period, potassium was transferred from the lower part to theupper part continuously and K accumulation of upper organs wasn’t affected by soil potassium levels’change（.6）The yields of soybean were different at different soil potassium levels. Potassium was usefulto improve yield of soybean and the yield showed an increasing tendency with the improvement of soilpotassium level. Yield would not increase when the soil potassium content reached312mg/kg. In thefield, yields of three soybean varieties were the highest when the potassium sulfate fertilizer level was150kg/hm2, and continuing to increase the potassium sulfate fertilizer level was useless to improve theyield of soybean.