The effect of long-term application of P fertilizer on soil grown forage plants
Date
2006-03-01
Authors
Nayyar, A.
Hamel, C.
Hanson, K.
Selles, F.
Jefferson, P.
Germida, J.
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Abstract
Phosphorus (P) fertilization does not always increase crop yields but the repeated use of P may modify the biological properties of soils. The objective of the present study,
therefore, was to investigate the effect of long term applications of P fertilizer on soil
biological properties. We used an experimental site located in Swift Current in which
different amounts of P (0, 20 and 40 kg P2O5 ha-1) were applied annually for the past 8
years on alfalfa and alfalfa-Russian wild rye hay crops. Our hypothesis was that repeated application of P influences soil microbial biomass and various soil enzymes. Microbial biomass C in the 0-7.5 cm soil layer was determined by fumigation-extraction at each of three harvest dates, and dehydrogenase, acid phosphatase and urease activities were assayed. Application of P to soil increased soil available P, dissolved organic C and available NO3-N, but did not significantly affect crop yields or soil microbial biomass C. Arbuscular mycorrhizal colonization of crop roots, and dehydrogenase and urease activities were decreased, suggesting that P reduced soil microbial activity. Acid phosphatase activity remained unchanged with P fertilization, suggesting that P availability was not limiting in these systems. While 8 years of application of P had little effect on hay yields, it generally reduced the activity of the soil microbial biomass.
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Keywords
phosphorus, dehydrogenase, urease, acid phosphatase, microbial biomass, soil biological activity
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Soils and Crops Workshop