Studies On Potassium Cycling In Plant-soil System And Its Relation To Kernel Yield And Quality In Winter Wheat

Effect of potassium application on potassium content in soil and potassium absorptionand partition in winter wheat were studied on different fields with different content ofavailable potassium from the point of view of potassium cycling in plant-soil system. And therelationship between nitrogen and potassium metabolism in wheat and the physiologicalmechanism how potassium affected kernel yield and quality in wheat were studied. Inaddition, different types of wheat varieties were classified based on there tolerance tolow-potassium stress and the effect of potassium on yield. And the different characters ofnitrogen and potassium metabolism of different types of wheat were analyzed. The mainresults were as follows:1. Effect of potassium application amount and stage on potassium cycling in plant-soilsystem Potassium accumulation amount in wheat came to the culmination at anthesis andafterwards the accumulation amount decreased. The ratio of potassium accumulation amountin the period from jointing to anthesis to the maximum of potassium accumulation amount isabout 60%. The potassium applied at jointing increased the potassium accumulation amountin wheat because its application stage was in the period when the wheat needs potassium most.And the potassium accumulation amount increased with the addition of potassium applicationamount. Higher soil potassium level accelerated the potassium accumulating, and as a resultthe potassium accumulation rate of Jimai20 came to the culmination earlier in field with highpotassium level (H-K) than in field with middle potassium level (M-K). Potassium was fixed more by the soil in the period from before winter to getting-up thanin the period from getting-up to maturity. And more potassium was applied before winter, 4山东农业大学博士学位论文more potassium was fixed. With the addition of potassium application amount, the content of available potassium insoil increased simultaneously before winter. The difference of the content of available pota-ssium in soil between different treatments before winter was reduced at getting-up stage as aresult of the fixation of potassium by soil. Potassium split application improved the content ofavailable potassium in soil at flagging stage through the top-dressing at jointing. Potassium split application decreased the potassium fixation in soil and increased thepotassium content in soil, which made it one of the effective measures to further the wheatpotassium absorption.2. Effect of potassium application amount and stage on nitrogen accumulation in wheatand on content of different form of nitrogen in soil Potassium applied one-stage had no significant effect on the amount of nitrogenabsorption. But for potassium split application, with the addition of potassium amount, theamount of nitrogen absorbed increased. Above 70% of nitrogen in wheat was derived fromsoil. Potassium split application increased the absorption both of fertilizer nitrogen and soilnitrogen at the same time, while the percentage of fertilizer nitrogen to total nitrogenincreased, and the percentage of soil nitrogen to total nitrogen decreased, so the soil nitrogendependent rate decreased. Compared with potassium applied one-stage, potassium splitapplication stimulated the absorption of nitrogen, increased the recovery in 0-25cm soil layerand the total recovery rate, and decreased the loss. Among the treatments with differentpotassium amounts, the treatment of 90kg K2O·hm-2 applied got the highest recovery rate insoil, the highest total recovery rate, and the lowest loss rate. Potassium application affectedmore on topdressing fertilizer than on basal fertilizer. Changing potassium applied one-stageto potassium applied before sowing and at jointing along with nitrogen decreased nitrogenloss, and strengthened the supply of soil nitrogen, that was the cause why potassium splitapplication increased the nitrogen absorption in wheat.