Study on the enhancement and mechanism of organic-inorganic compound fertilizer on inorganic fertilizer utilization III. Effect of potassium sulfate combined with organic material on maize yield and K fertilizer utilization

【Objectives】 Fewer researches have been done systemically on the adjustment of organic-inorganic recombination on the chemical K use efficiency. The study on the K efficiency of potassium sulphate after granulated with sugar residues in different ratios will be helpful to understand the beneficial mechanism of yield and profit increase of organic-inorganic compound fertilizer.【Methods】Three kinds of organic-inorganic compound K fertilizers were made via mixing sugar residues from monosodium glutamate factory with potassium sulfate in 3:1, 1:1 and 1:3(w/w) and granulated using pan granulator. A pot experiment was carried out using the three compound K fertilizers and potassium sulphate. Three total K input levels of K2O 75, 150 and 225 kg/ha were designed for each tested fertilizer, and the same input level of sugar residues without K was used as the corresponding control of the compound K fertilizer to eliminate the possible effect by organic materials. The crop yield, K uptake, K use efficiency were investigated. 【Results】 1) The maize grain yield was increased by 11.36% in average with application of compound K fertilizer. The maize grain yield was increased by 27.75% and 10.77% at the low and high input rates of compound K fertilizer, but decreased by 3.24% at medium input level, compared to potassium sulfate. 2) Application of compound K fertilizers could increase the K uptake of maize plant by 11.43% in average. The K uptake of maize plant was increased by 31.32% and 16.11% at the low and high K inputs of compound K fertilizers, but decreased by 9.11% at medium input, compared to potassium sulphate. 3) The increase of K uptake by maize plant with the application of compound K fertilizers was 11.92% higher than corresponding organic material treatments in average, which exceed the K uptake increase with potassium sulfate to the no K control. 4) The average K recovery of the three compound K fertilizers input rates was 17.92 percentage points higher, compared to potassium sulfate. Under the same total K input, inorganic-K recoveries were increased at both the low and high rates, but not at medium rate.【Conclusion】 The combination of sugar residue and potassium sulphate could effectively increase the K use efficiency in general. Comprehensive considering the yield and utilization of K,the relatively appropriate mix ratio of sugar residues and potassium sulphate should be in 1:3 (w/w), and the application rate of the compound K fertilizer should be less than normal chemical K fertilizer under the similar soil condition tested.