Effects Of Polyhalite On Crop Growth

Polihalite（K₂Ca₂Mg[SO₄]₄·2H₂O）is a kind of mineral which is rich in potassium,calcium,magnesium,sulfur and other elements.There is a large amount of deposit and is widely distributed in China.So the polyhalite is a potential potash resources which can solve the present potash supply shortage in China.The properties of polyhalite and its effects were studied,but the research design was relatively simple.There is rare report about its nutrient release characteristics,the correlations of nutrients and differences with other fertilizers.So the nutrient realease properties of polyhalite,its effect on plant（eggplant,corn and peanut）growth,its nutrient uptake and the differences of polyhalite with commercial fertilizers were studied in this paper,with methods of soil culture,seed germination investigation and pot experiment.The purpose of this study was to provide some theoretical basis for the application of polyhalite in agriculture.The main research results are as follows:1.Potassium,calcium and magnesium in polyhalite were all available nutrients and their one day release rate in soil was 100%.The release rate of sulfur was up to 86%.With the extension of incubation time,parts of the available nutrients were fixed by soil colloid.In about 28 days,the soil nutrient content was stable.2.With the increase in extract concentration,germination rate,shoot length and root length of corn seeds decreased,but the salt injury index of corn seeds increased.Salt injury index of corn seeds had extremely significant negative correlations with germination rate,shoot length and root length of corn seeds.When fertilizer extract concentration was less than 0.1%,polyhalite had no significant difference with other commercial potash fertilizer in seed germination.When the fertilizer extract concentration was above 0.5%,the seed germination rate of polyhalite treatment was lower than that of other commercial potash fertilizer treatment,and the difference was significant.3.Polyhalite could increase the yield of vegetables,food crops and oil crops and promote there nutrient content.Polyhalite affect the biological properties of eggplant.Eggplant with dosage of 300 kg·hm^-2（K₂O）and 700 kg·hm^-2（K₂O）at seedling stage and mature stage respectively had a better growth performance in biological properties and nutrient content.In the treatment of 100 kg·hm^-2（K₂O）polyhalite dosage,corn and peanut showed the best performance in plant growth,nutrient content,grain weight and full fruit rate.4.Polyhalite decreaed soil pH and raised soil EC.Soil pH was about 5.90 and soil EC about 1100 μS·cm-1 after 28 days of polyhalite application.During all the time of the culture process,polyhalite treatment all had a lower soil pH and a higher soil EC than other tratments with commercial potash fertilizers.The moere polyhalite applied,the more significant its effect was on soil pH and soil EC.5.After crop harvest,the potassium remaining in the soil for corn and peanut experiment decreased with the increase in application level and the difference with control was not significant.The potassium remaining in the eggplant soil increased with the increase in application level and the difference with control was significant.