磷矿粉在橡胶园不同母质砖红壤中溶解特性研究

Dissolution characteristics of phosphate rocks in latosols with different parent materials in rubber plantations

研究表明大多数热带地区酸性土壤上施用磷矿粉能取得与水溶性磷肥相当的肥效。目前橡胶树等热带作物施肥实践中长期施用水溶性磷肥,磷矿粉在热带胶园土壤中的应用研究较少。为此,本文通过室内培养试验研究了采自云南昆阳磷矿(KPR)和江西吴村磷矿(WPR)2种品位磷矿粉在砂页岩、花岗岩、片麻岩、浅海沉积物和玄武岩等5种母质发育的10个胶园砖红壤中的溶解特性和有效性动态变化。结果表明:2种磷矿粉在10个砖红壤上的溶解量均随着培养时间的延长不断增加。对2种磷矿粉在砖红壤中的溶解动力学过程模拟效果最好的是Elovich方程,其次是Langmuir方程,Mitscherlich方程模拟效果最差。2种磷矿粉在玄武岩发育砖红壤上平均最大溶解量分别是砂页岩发育砖红壤、花岗岩发育砖红壤、片麻岩发育砖红壤和浅海沉积物发育砖红壤的2.16倍、1.73倍、2.49倍和2.39倍。2种磷矿粉在10个土壤中最大溶解量均与土壤有机质含量、水解性总酸、游离态氧化铁含量和CEC呈显著性正相关,溶解速率均与土壤水解性总酸、游离氧化铁和CEC呈显著正相关关系。经逐步回归发现:土壤游离氧化铁含量可能是决定磷矿粉在砖红壤中最大溶解量的第1因素,土壤磷吸附常数K值和CEC则可能分别是影响KPR和WPR在砖红壤中溶解速度的第1因素。2种磷矿粉施用后所有土壤有效磷含量均出现不同程度的增加,但不同土壤、不同培养时间有效磷增加量存在差异。本研究显示,将磷矿粉优先施用在玄武岩发育砖红壤可能会取得相对较好的效果;与KPR相比,WPR作为中低品位磷矿粉也可能同样有效。

Latosols are very acidic, often extremely deficient in phosphorus （P） and have strong P sorption capacity. The state of P in latosols is one of the main limiting factors of growth and yield of rubber trees. Several studies have suggested that phosphate rocks （PR） could be as effective as water soluble phosphate fertilizers in increasing plant yield and improving soil P content in tropical regions. Although water soluble P is the mainly P fertilizer used for improving the state of nitrites in rubber trees, rational use of PR has not been intensively researched. PR application proved promising particularly in tropical plantations and organic agriculture in China. This research simulated and assessed dissolution and availability extents and rates of two PR forms in different latosols from five parent materials. The research also identified major soil factors controlling PR dissolution and availability in tropical soils. The results provided useful information on rational application of PR in tropical crops in China. Thus the dissolution and availability characteristics of two PR forms [Kunyang phosphate rocks （KPR） from Yunnan Province and Wucun phosphate rocks （WPR） from Jiangxi Province] were investigated in laboratory incubation often rubber plantation latosols with different parent materials. PR was added to tropical soils at rates of 0 mg（P）＇kg-1 （control） and 500 mg（P）·kg-1. The soil-PR mixtures were placed in plastic containers and incubated at moisture content of==60% soil water-holding capacity, 25℃ and for 35 days. Results showed that dissolution of twoforms of PR increased in all the soils with increasing incubation period. The two PR dissolution kinetics in ten types of latosols were best described by the Elovich equation, followed by Langmuir equation. The Mitscherlich equation did not suitably describe PR dissolution in latosols. Average maximum dissolution potentials of the two PRs in latosols from basalt were 2.16, 1.73, 2.49 and 2.39 times of latosols from sand shale, granite, gneiss and nerite, respectively. Maximum dissolutions of the two PRs in latosols were positive correlated with soil organic matter, soil total hydrolytic acidity, free iron oxide content and cation exchange capacity （CEC）. Dissolution rates of the two PRs in latosols were positive correlated with soil total hydrolytic acidity, free iron oxide content and CEC Stepwise multiple regression indicated that soil free iron oxide content was the soil factor with the most significant control over maximum dissolutions of the two PRs. CEC and soil adsorption parameter （K） were respectively the soil factors with the most effect on KPR and WPR dissolution rates in latosols. Soil available P increased after PR application, but the increment was different for the various soils and sampling periods throughout the incubation process. This study thus indicated that better effect was obtainable when PR was applied first in latosols from basalt. Compared with KPR, it was possible for low grade WPR to have the same effect regarding increasing soil available P in latosols.