Soil nitrogen fertility level

Sander and Schwelnsbergi reported that nitrite levels in soil were low even in the presence of large amounts of nitrogen fertilizers. The general rule seems to be that N02" levels in normal, aerobic soils are undetectably low, but they may temporarily increase in special circumstances. 

Applications of Fertilizers for Control of Rice Diseases. In general, the application of fertilizers cannot be relied upon to solve all our major rice disease problems however, the application of properly balanced fertilizers reduces the severity of certain major diseases. Work on stem rot (Leptosphaeria salvinii Catt.) in Arkansas (3) and Japan (26) shows that the severity of stem rot can be reduced by increasing the potassium levels of soils in the problem areas. In Arkansas it has been shown that the application of nitrogenous fertilizer significantly increases stem rot severity, whereas the application of potassium fertilizer alone or in combination with nitrogenous fertilizers decreases stem rot severity. Consequently, in Arkansas the application of potassium fertilizer is widely practiced for stem rot control. 

Clements R. O., Murray P. J., and Sturdy R. G. (1991) The impact of 20 years absence of earthworms and three levels of nitrogen fertilizer on a grassland soil environment. Agri. Ecosys. Environ. 36, 75-86. 

Carrots re re moderate to high levels of potassium and phosphorus, but only moderate le elsof nitrogen, so avoid high-nitrogen fertilizers. Carrots are very sensitive to salt injury and do poorly in soils with high sodium levels. 

Figure 13.11 Ammonia is essential in the production of fertilizers containing nitrogen. Proper levels of soil nitrogen lead to increased crop yields. 

Figure 3.12. Effect of different levels of nitrogen applied to the soil on ricinine content L— low level of nitrogen fertilization (none) M—medium level of nitrogen fertilization (250 kg N/ ha) H— high level of nitrogen fertilization (500 kg N/ha). (Nowacki and Waller 1972). Courtesy of the publisher.

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