| This study was based on two long-term experiments which located at Qiyang and Jinxian red soil experimental stations, and the start times were1990and1986respectively. No potassium (K) fertilization (no fertilization (CK), single nitrogen (N), single phosphorus (P) and nitrogen combine with phosphorus (NP)), single chemical K fertilization (single chemical potassium fertilization (K), nitrogen combine with potassium (NP), NP combine with potassium (NPK), higher rate of NPK (HNPK), and NPK combine with straw (NPKS)), and manure (NPK combine with manure (NPKM), single manure (M), and1.5times NPKM (1.5NPKM)) were used in this study. The amount of soil potassium and the form of soil clay mineral change under different fertilizations over20years were studied. The distribution of soil available, slowly-available, and total potassium in different sizes of organo-mineral complex were studied at inside laboratory. Study the kinetics of non-exchangeable potassium release, and the availability of soil potassium under long-term fertilization combined with soil acid affected. The main results and conclusions shown as follows:(l)Changes of the content of soil potassium under long-term fertilizationManure could increase soil available potassium more sharply than single chemical potassium fertilizer. The increase rate of single chemical potassium fertilizer and manure were5.76-8.16and5.10-14.02mg/kg-a respectively. The average increasing rate under manure treatments at Qiyang site was higher than that at Jinxian site, and higher than single chemical potassium fertilizer.The content of slowly-available potassium under long-term no potassium and single chemical potassium treatments were both decreased, the decrease rate at Qiyang was5.76-8.16and2.61-13.71mg/kg-a respectively. Chemical potassium fertilizer treatments could slow down the decrease rate of slowly-available potassium, however manure treatments had the lowest slowly-available potassium decrease rate.(2)Long-term potassium fertilization could slow down or stop the transform from2:1type clay minerals to1.4nm transition mineral or even to1:1typr clay minerals. The soil at Qiyang site which contains more kaolinite, and the content of mica had decreased by22.90g/kg, and1.4nm transition mineral had increased by1.27g/kg under NP treatment after21years fertilization compared with original value, but NPK and NPKM had increased the content of mica by29.38and28.19g/kg respectively, and1.4nm transition mineral decreased by12.16and17.57g/kg respectively. Long-term no potassium fertilization caused the release of potassium from mica, and induced the transformation from mica to kaolinite, however, long-term potassium input could slow down or stop this transformation or overturn the transformation process.(3)Long-term fertilization induced the content of exchangeable and non-exchangeable potassium change mainly appeared at<2μm organo-mineral complex. NPK and NPKM increased the content of available potassium by36.71～147.39mg/kg, and the increase ratio were15.7%-151.1%compared with NP. Similar to Jinxian site, NPK and NPKM treatment increased the content of available potassium by 52.85-219.51mg/kg, and the increase ratio were47.6%-96.9%, compared with NP. The content of non-exchangeable potassium at<2μm under NPK and NPKM at Jinxian site was higher than the same treatments at Qiyang site, however the content of available potassium at<2μm under NPK and NPKM at Jinxian site was lower than at Qiyang site.(4)The accumulation of non-exchangeable release at300hours among different treatment follows: NPKM> NPK> NP> CK at Jingxian site, and NPKM> NPK> CK> NP at Qiyang site respectively. The accumulation of non-exchangeable K release between different sizes of organo-mineral complex at both sites follows:(<2μm)>2～10μm>10～50μm,(>100μm)>50-100μm.(5)Both long-term fertilization and soil acidification influenced the availability of soil potassium. After the first harvest, there was a boundary at pH5.0under potassium application. The content of available potassium at pH4.0-5.0was higher than that of5.5～6.5respectively, while plants could uptake more potassium at pH5.5-6.5than that of4.0～5.0respectively. The accumulation of potassium plants uptake after five harvests at different treatments followed by, NPKM>NPK>CK>NP. The highest potassium support pH was pH6.0.Above all, long-term potassium application increased the content of potassium, while slowed down the decrease rate of the content of soil slowly-available and total potassium. Long-term no potassium application treatments increased the release of soil mineral potassium, and changed the form of clay mineral. Potassium fertilizer application could increase the content of soil potassium especially at<2μm. Based on the non-exchangeable potassium release character, long-term potassium fertilization had a bigger potassium suppolying capacity. Chemical potassium application especially chemical potassium combined with manure had a bigger potassium suppolying capacity at pH6.0. |
