Soil phosphorus pool and the living phase response to phosphorus supplementation

The results of studying the response of the living phase of soils with different phosphorus content to the application of phosphate fertilizer (PF) are presented. The changes of soil phosphatase activity and the number of phosphate solubilizing bacteria CFU during the phosphorus fertilization were studied. The soil used for the experiment is - leached medium-loamy chernozem of the Novosibirsk Ob region. Soil samples were collected in the Novosibirsk region: soil 1 - on the territory of the farm “Elitnayaˮ Novosibirsk district, (geographical coordinates 54.87° N, 82.91° E), soil 2 - of the farm “Proletarskyˮ Ordynsky district, (54.38° N, 81.16° E). The content of total phosphorus in the samples was 0.225 and 0.175%, respectively. The soils involved in the experiments are well provided with mobile phosphorus, determined by the Chirikov method, and according to the standard scale, do not need phosphorus fertilizer. However, the soils differed significantly in the fractional composition of phosphorus pool. According to the methods based on salt und buffer extracts, soil 1 is assigned to the “medium” phosphorus supply gradation, and soil 2 is “low”. Experience scheme 1 - N60 (control), N60Р60; N60Р120; scheme 2 - N100 (control), N100P60. The introduction of P60 and P120 in soil 1 did not affect the value of the wheat biomass, in soil 2 - at P60, the biomass increased by 1.4, and at P120 - by 2.7 times. The removal of phosphorus in the soil 1 increased by 1.9 times, in the soil 2 - by 2.7 times compared with the control variant. In soil 1, the phosphatase activity and the number of phosphate solubilizing bacteria did not change during fertilization, in soil 2, the phosphatase activity decreased by 15% and the number of CFU increased by 5 times. It is concluded that the response of phosphatase activity and CFU to the introduction of phosphorus fertilizer depends on the content of mobile phosphorus in the soil and is determined by the ability of the solid phase of the soil to fix the phosphorus introduced with the fertilizer.