施磷量和灌溉方式对水稻磷素吸收利用的影响

【目的】探明施磷量和灌溉方式对水稻分蘖期、拔节孕穗期磷素吸收利用的影响。【方法】以杂交稻C两优608为材料进行盆栽试验,分别设置P1(0 g/kg)、P2(0.18 g/kg)、P3(0.36 g/kg)、P4(0.54 g/kg)4个施磷水平,及干湿交替灌溉(AI)、增氧+干湿交替灌溉(AO)2种灌溉方式,系统研究了分蘖期及拔节孕穗期水稻土壤有效磷量、植株磷素吸收特性的变化及其相关性。【结果】无论是分蘖期还是拔节孕穗期,地上部磷吸收量均高于地下部,拔节孕穗期各器官磷吸收量、植株磷累积量均高于分蘖期。施磷、灌溉方式对水稻各器官磷吸收量、植株磷累积量、土壤有效磷量及磷吸收利用率影响极显著;施磷与灌溉互作对各器官磷吸收量、植株磷累积量、土壤有效磷量及分蘖期磷吸收利用率影响极显著,增氧+干湿交替灌溉下拔节孕穗期P3水平水稻磷累积量、磷吸收利用率均最高,分别为0.218 g/株、19.33%。干湿交替灌溉下土壤有效磷量与植株磷累积量、各器官磷吸收量极显著正相关;灌溉方式显著提高水稻根系对磷的吸收量;增氧+干湿交替灌溉方式下拔节孕穗期土壤有效磷量与磷吸收利用率显著负相关。【结论】增氧+干湿交替灌溉方式配施磷量0.36 g/kg时,水稻拔节孕穗期植株磷累积量最高。

Inorganic Phosphorus Fractions and Phosphorus Availability in a Calcareous Soil Receiving 21-Year Superphosphate Application

A long-term （21-year） field experiment was performed to study the responses of soil inorganic P fractions and P availability to annual fertilizer P application in a calcareous soil on the Loess Plateau of China. Soil Olsen-P contents increased by 3.7, 5.2, 11.2 and 20.6 mg P kg-1 after 21-year annual fertilizer P application at 20, 39, 59, and 79 kg P ha-1, respectively. Long-term fertilizer P addition also increased soil total P and inorganic P （Pi） contents significantly. The contents of inorganic P fractions were in the order of Ca10-P 〉 Cas-P 〉 Fe-P 〉 A1-P 〉 occluded P 〉 Ca2-P in the soil receiving annual fertilizer P application. Fertilizer P application increased Cas-P, A1-P and Ca2-P contents as well as their percentages relative to Pi. Pi application increased Fe-P and occluded P contents but nor their percentages. Soil Ca10- P content remained unchanged after fertilizer P application while its percentage relative to Pi declined with increasing fertilizer P rate. All Pi fractions but Ca10-P were correlated with Olsen-P significantly. 90% of variations in Olsen-P could be explained by Pi fractions, and the direct contribution of Cas-P was predominant. Long-term annual superphosphate application would facilitate the accumulation of soil Cas-P, and thus improve soil P availability.

Impact of Intensive Greenhouse Production System on Soil Quality

Composite top- and subsoil samples were collected from the greenhouses in the Al-Balawneh area,Jordan,where intensive greenhouse production system(IGPS) has been practiced since 1998,to study the impact of IGPS on soil quality as measured by the chemical and biological properties to develop a sustainable production system.The study showed that IGPS led to higher electrical conductivity in top- and subsoils compared to an uncultivated soil(control).Quality and amount of irrigation water,lack of efficient drainage,and quantity and types of applied fertilizers were major factors resulting in salt buildup.IGPS resulted in lower total N(TN) and NO_3-N in the soil compared to the control.The lower TN was due to crop uptake,microbial immobilization,volatilization,and irregular application of composted animal manure or poultry manure.In contrast,higher residual Olsen-P content was detected in both soil layers of greenhouses than in the control.Residual P was classified as very high in the topsoil layers and sufficient to high in the subsoil layers.Residual available K in the soils of greenhouses was relatively lower than that in the control and it was,however,classified as high to very high.A large increase of Cl and a considerable decrease in the bacterial count were observed in both soil layers of IGPS compared to the control treatment.Economically sustainable soil management practices need to be adopted by farmers to achieve a sustainable and profitable production.This can be accomplished through education,targeted towards the farming community in the central Jordan Valley.