Phosphorus status of Philippine rice soils with different clay mineralogical characteristics

Bajwa, M. I.

doi:10.1007/bf01048946

Cited by 3 publications

(1 citation statement)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While BC is also influenced by soil texture, the observation that the texture component was significant at all N rates suggests that the main role of sand and clay involved their impact on ammonia diffusion through the soil profile (Wang & Alva, 2000; Mroczkowski & Stuczyński, 2006). Thus, the small ammonia levels in soil 13 are because of the presence of amorphous clays such as allophane and imogolite, which limit diffusion and increase both CEC and BC (Bajwa, 1982; Buresh, 1987). In contrast, the large ammonia levels arising from soils 8 and 6 are a function of their sand content (710 and 970 g kg −1 , respectively), which allows for rapid diffusion and minimal buffering capacity.…”

Section: Discussionmentioning

confidence: 99%

Ammonia toxicity in aerobic rice: use of soil properties to predict ammonia volatilization following urea application and the adverse effects on germination

Haden

Xiang

Peng

et al. 2011

European Journal of Soil Science

View full text Add to dashboard Cite

Recent studies indicate that aerobic rice can suffer injury from ammonia toxicity when urea is applied at seeding. Urea application rate and soil properties influence the accumulation of ammonia in the vicinity of recently sown seeds and hence influence the risk of ammonia toxicity. The objectives of this study were to (i) evaluate the effects of urea rate on ammonia volatilization and subsequent seed germination for a range of soils, (ii) establish a critical level for ammonia toxicity in germinating rice seeds and (iii) assess how variation in soil properties influences ammonia accumulation. Volatilized ammonia and seed germination were measured in two micro-diffusion incubations using 15 soils to which urea was applied at five rates (0, 0.25, 0.5, 0.75 and 1.0 g N kg −1 soil). Progressively larger urea rates increased volatilization, decreased germination and indicated a critical level for ammonia toxicity of approximately 7 mg N kg −1 . Stepwise regression of the first three principal components indicated that the initial pH and soil texture components influenced ammonia volatilization when no N was added. At the intermediate N rate all three components (initial pH, soil texture and pH buffering) affected ammonia volatilization. At the largest N rate, ammonia volatilization was driven by soil texture and pH buffering while the role of initial pH was insignificant. For soils with an initial pH > 6.0 the risk of excessive volatilization increased dramatically when clay content was <150 mg kg −1 , cation exchange capacity (CEC) was <10 cmol c kg −1 and the buffer capacity (BC) was <2.5 cmol c kg −1 pH −1 . These findings suggest that initial pH, CEC, soil texture and BC should all be used to assess the site-specific risks of urea-induced ammonia toxicity in aerobic rice.

show abstract

Section: Discussionmentioning

confidence: 99%