Effects of Freezing and Thawing on Soil Phosphorus of Protective Farmland

Abstract

Freezing and thawing of soil is an abiotic stress, and has direct effect on chemical properties, physical properties and biological properties. In order to research effect of freezing and thawing on soil chemical properties, experiments of freeze-thaw cycle were simulated, and different forms phosphorus was measured. Results show that freezing and thawing made water-soluble and loosely combined phosphorus content decrease, but made calcium P content increase. Low-strength freezing and thawing cycle made aluminum P content increase, but made iron P content decrease. To soil of low accumulation phosphorus, low-strength freezing and thawing made occluded P content decrease and be released, but high-strength freezing and thawing made occluded P content increase. Inorganic phosphorus content had an ascending trend with enhancing of freezing and thawing, but organic phosphorus content had a descending trend. Under low-strength freezing and thawing, available P content of soil of low accumulation phosphorus had an ascending trend, and available P content of soil of high accumulation phosphorus had a descending trend, but available phosphorus content had no great changes when strength of freezing and thawing continued to increase.