• ISSN 1008-505X
  • CN 11-3996/S
WU Bo, WU Fa-qi, TONG Xiao-gang, SONG Min-min, HOU Lei. Spatio-temporal variability of phosphorus content in cultivated soils in Nihegou watershed in recent 40 years[J]. Journal of Plant Nutrition and Fertilizers, 2019, 25(5): 851-858. DOI: 10.11674/zwyf.18127
Citation: WU Bo, WU Fa-qi, TONG Xiao-gang, SONG Min-min, HOU Lei. Spatio-temporal variability of phosphorus content in cultivated soils in Nihegou watershed in recent 40 years[J]. Journal of Plant Nutrition and Fertilizers, 2019, 25(5): 851-858. DOI: 10.11674/zwyf.18127

Spatio-temporal variability of phosphorus content in cultivated soils in Nihegou watershed in recent 40 years

  • Objectives Phosphorus is one of the limiting factors in the agricultural production of the Loess Plateau. It is of great significance to study the temporal and spatial variation of soil phosphorus content in the cultivated land of harnessed small watershed for the evaluation and management of cultivated land in this area.
    Methods From 1980 to 2005, five field surveys had been carried out and total of 457 soil samples were collected at different time and space scales within Nihegou watershed, the soil total phosphorus and Olsen-P contents were analyzed. The variation of soil P was calculated and summarized by detailed experiments, micro-analysis and information feedback test, and the causes of the variation were discussed.
    Results As viewed from the time, the soil total-P content of cultivated land showed an accelerated decline in the past 40 years, and the soil Olsen-P content showed a fluctuating change of first rising and then decreasing. The time variation of total-P content in soil was related to the change of crop yield and phosphorus application rate. Because farm manure and phosphorus fertilizer were more applied to cultivated land from 1980 to 1998, the “input” and “output” of phosphorus in all soils were more balanced, and soil total-P content was stable between 1.31 g/kg and 1.34 g/kg. The time variation of soil Olsen-P content was related to the change of fertilizer structure and available phosphorus fertilizer application rate. As the input of available phosphorus fertilizer per hectare in cultivated land was increased by 120 kg from 1980 to 2004, the soil Olsen-P content was increased by 2.6 times. From 2004 to 2015, due to the promotion of compound fertilizer, the application rate of phosphate fertilizer decreased, and the soil available phosphorus content was decreased by 24.7%. As viewed from the space, the spatial variability of soil phosphorus cont was mainly affected by soil erosion and land management. The content of phosphorus in sloping farmland was higher than that on slope. The whole slope surface shows flat land > gully upper land > gully bottom land > gully slope land. Because soil erosion on uniform sloping farmland causes one-way transport of sediment and nutrients along slopes, and the mobility of Olsen-P was higher than that of total-P. The land close to the watershed on the whole slope section was managed more carefully because of its close proximity to the residential area, and the soil fertility was high. The soil Olsen-P content was more than one times higher than that in other cultivated land. Through harnessing, the topographic conditions of cultivated land in the whole basin gradually narrowed, the terrace area increased from 100 hm2 in 1980 to 250 hm2 at present, and the slope farmland area decreased from 250 hm2 in 1980 to 50 hm2 at present. Under the influence of soil disturbance, the phosphorus content in newly constructed terraces was close to parent material and lower than that in old terraces and sloping fields.
    Conclusions After nearly 20 years of harnessing and more than 10 years of socialized and free management, the soil total-P content shows a downward trend. The soil Olsen-P content mainly depends on the supply of available phosphorus fertilizer, which will be a major hidden danger for the development of agriculture in the basin. With the seasonal flow of rural labor force, cultivated land management needs to be optimized on the basis of saving labor and time. Adjusting fertilizer structure and realizing intensive management will be an important direction for agricultural development in the future.
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