Changes in soil phosphorus pools of grasslands following 17 yrs of balanced application of manure and fertilizer

Abstract

Limiting the use of phosphorous (P) in intensive agriculture is necessary to decrease losses to surface waters. Balanced fertilizer application (P supply equals P offtake by the crop) is a first step to limit the use of P. However, it is questioned whether this balance approach is sufficient to maintain soil fertility. A long-term field experiment (17 yr), on grazed grassland, has been conducted on sandy soil, marine clay soil and peat soil to obtain insight into the effects of balanced P fertilizer application on soil test P values and to explain the results by changes in P pools in the soil. The balance approach led to a gradual decline in plant available P, measured as P-AL, in the topsoil (<0.10 m deep). This decline was accompanied by a decline in oxalate extractable P, dithionite extractable P and inorganic P (0.5 M H 2 SO 4 ). The decline in these mineral P pools in the topsoil was (partly) compensated by an increase in the amount of organic P. There was evidence for the accumulation of P in an occluded form, especially at one of sites which received P as Gafsa rock phosphate [Ca 3 (PO 4 ) 2 ].

Impacts of long-term inorganic and organic fertilization on phosphorus adsorption and desorption characteristics in red paddies in southern China

“…P supply will limit increases in agricultural production worldwide in the coming decades. Excessive usage of fertilizers to overcome P deficiency has led to many problems, such as P accumulation in the soil system and surface water runoff [ 3 , 4 ]. Red soils, having a low or acidic soil pH, are widely distributed in the southern part of China.…”

Artificial humic substances improve microbial activity for binding CO2

“…P is one of the most important elements in the biosphere and agriculture, especially for promoting plant growth (Quanxian et al, 2008). However, excessive use of phosphate fertilizers induces remineralization iScience Article and P accumulation in soils; only a small and variable fraction of the added P is directly available to the plants ( Van der Salm et al, 2017). It is because soil contains a large amount of iron and aluminum oxides, and once applied phosphate fertilizer enters the soil, it will be fixed to form insoluble P (Yang et al, 2021a).…”

Testing soil phosphorus in a depleting P scenario: an accelerated soil mining experiment

“…This reflects the differences in P pools measured by these tests: P‐AL is a more buffered method, whereas the aggressive ammonium oxalate extraction is a measure for total soil P. That ΔP‐Ox exceeds the cumulative shoot P uptake (+N treatment) can be partly explained by underestimation of the total cumulative P uptake because the P uptake by roots was not included. Alternatively, part of the extractable P at the start of the pot trial can become unavailable for the acid ammonium oxalate extraction because of a transformation to non‐extractable P forms, for example because of the stronger binding and accumulation of P in inorganic forms or in organic material (Van der Salm et al ., ). For the +P treatment, the mass balance (calculated as P fertilizer application minus cumulative P uptake) was positive (i.e.…”

“…A similar gap between the mass balance and Δ P values has been observed in other pot trials for the oxalate (Koopmans et al ., ) and Olsen extractions (Schelfhout et al ., ). In field studies, a decrease in soil P availability larger than the mass balance has also been observed (Gallet et al ., ; Van der Salm et al ., ). In the present study, the mass balance of the Olsen extraction was smaller than the cumulative P uptake.…”