Influence of long-term N-P fertilizers, cropping systems and rainfall on corn yields and on soil properties
1987
Tattao, Dante A.
Studies were made on a Pakchong clay, Reddish Brown Lateritic soil (Paleustult) at the National Corn and Sorghum Research Center, Pakchong, Nakhon Ratchasima, Thailand. When the soil was low in fertility, grain and stover yields did not correlate with rainfall. However, at high levels of N-P2O5 fertilization, the yield responded to rainfall. The highest agronomic yield occurred with the addition of 120-120 fertilizer while the best economic yield was obtained with fertilization of 90-90 kg N-P2O5. Rotation cropping of either mungbean or peanut with corn without N-P fertilizer gave comparable corn yield with the fertilized sole crop of corn, whereas rotation of soybean without fertilizers gave yield comparable to unfertilized sole corn. Without N-P fertilizers, intercropping with soybean, peanut or mungbean gave corn grain yields comparable to sole corn. With N-P fertilizers rotation or intercropping either of the three legumes gave corn grain yield comparable to yield of sole corn. Addition of fertilizer decreased the pH of the soil which may have aggravated the leaching of Ca and Mg. Insignificant differences in aggregation were found among cropping systems. However, degradation in aggregation were noticed when fertilizer was applied. Mycorrhizal and Azotobacter, populations were highest in the corn-mungbean rotation system. The presence of legumes either as intercrops or as rotation crops increased Azotobacter population. Annual application of 94-94 kg N-P2O5/ha did not affect mycorrhizal population but decreased Azotobacter population.
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