Abstract
Synthetic sheep urine additions (59 g N m−2) were made to pastures on two soils, at Fasset, a semi-natural grassland, and Strathfinella, an improved pasture. Urine was applied to microplots in May and the soil, grass and soil solution analyzed 1, 2, 4, 5, 12 and 23 weeks after the addition. At Fasset, the grass was scorched by urine and the standing biomass decreased compared to the control, increasing only after 5 weeks. The absence of scorching at the Strathfinella site was attributed to a greater biomass of root mat to buffer the roots from exposure to NH3and a greater rainfall immediately following treatment. Scorching reduced the uptake of N and it was not clear if the greater contents of NH4 + and the increases in soil pH at Fasset compared with Strathfinella were the causes or symptoms of the scorch effect. Amounts of extractable organic N (DON) were similar in both soils and increased during the first 4 weeks and then decreased. Urine addition both increased and decreased DON at different times, but the overall mean values were unchanged. Urine application changed the distribution of P in the two soils, increasing the soil solution P at Fasset by 80 mg P m−2 and raising the P content of herbage at Strathfinella by 600 mg P m−2. In the soil solution, dissolved forms of molybdate reactive P, organic P and condensed P fractions were all increased by the urine addition. After 23 weeks, condensed P made the greatest contribution to soil solution P in both soils indicating that this fraction was the least available for plant uptake.
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Williams, B.L., Shand, C.A., Sellers, S. et al. Impact of synthetic sheep urine on N and P in two pastures in the Scottish uplands. Plant and Soil 214, 93–103 (1999). https://doi.org/10.1023/A:1004785808259
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DOI: https://doi.org/10.1023/A:1004785808259