Organic Phosphorus Forms in Agricultural Soils under Mediterranean Climate
Citation
Recena, R., cade-Menun, B.J., Delgado, A. (2018). Organic Phosphorus Forms in Agricultural Soils under Mediterranean Climate, 82(4), 783-795. http://dx.doi.org/10.2136/sssaj2017.10.0360
Plain language summary
Phosphorus (P) is an essential element for all plants, and fertilizers must be applied to many soils to sustain crop yields. However, the rock phosphate used to produce P fertilizers is a non-renewable resource, so there is interest in improving crop use of soil P. Organic P (P bound to carbon) can be a significant proportion of the total P in soils; if the organic P in soil can be converted by soil microbes into forms of P that plants can use, it may cut down on the amount of fertilizer needed to grow crops. This study looked at the forms of organic P in soils under the types of agricultural crops in Spain, annual field crops, vineyards and olive orchards, using soils with high and low soil test P concentrations. The results showed that organic P was contributing to the P available to plants, especially in the low-P soils. This indicated that the need for P fertilizers could be reduced in soils by management practices that increased the conversion of soil organic P into plant-available P, such as leaving crop residues in the field rather than removing them during harvest.
Abstract
© Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved. future sustainable phosphorus (P) management in agriculture will require a full understanding of the effects of agricultural practices on soil organic P (OP) speciation in different regions. This work studied the effects of land use, available P status, and soil properties on OP forms in Spanish agricultural soils under Mediterranean climate. We used31P nuclear magnetic resonance spectroscopy to characterize P in eight soils under two types of land use (field crops and olive or vine orchards), using two samples with different soil Olsen P status (“low” and “high” P samples) per soil type. Orthophosphate monoesters dominated OP in these soils, and inositol hexakisphosphates (IP6) were the most abundant identified group of monoesters. Land use affected total OP concentrations mainly through crop residue incorporation. The contribution of monoesters, including myo-IP6, to total OP increased with higher Olsen P concentrations, but only in soils from orchards. Degradation of monoesters including IP6 occurred under conditions of P limitation, suggesting some contribution of these OP forms to the plant P supply. Total IP6 was mainly related to poorly crystalline iron (fe) oxides, whereas other monoesters were related to crystalline fe oxides and to active ca carbonate equivalents. The dominant fe oxide type, carbonates, and the low accumulation of crop residues explained the relative contents of different OP forms in these Spanish soils compared with soils from other geographical areas. The effect of oxides in the accumulation of different OP forms was attributed to the affinities of these forms for oxides and to differences in the density of binding sites depending on the oxide type.