Uptake process and recovery of co-situs applied polyolefin-coated urea as affected by release pattern on corn (Zea mays L.) under humid climate in northeastern Japan
2008
Kanno, H.(Tohoku Univ., Sendai (Japan))
Two years of field experiments were conducted to (i) determine dent corn (Zea mays L.) growth and nitrogen (N) uptake from split-dressed urea, co-situs applied polyolefin-coated urea with linear (POCU-70) and sigmoidal (POCU-30+S60) release using the sup(15)N tracer method, and (ii) compare the uptake process and the recovery of co-situs applied POCUs in 1994 and 1995 at the Kawatabi Experimental Station of Tohoku University, located in northeastern Japan. The differences in the dry-matter production and total N uptake among the N sources were very small. However, the dry-matter production in 1994 is significantly higher than in 1995 due to unusual low rainfall and rich sunshine. During the early growth stage, the relative recoveries of POCU-70 and POCU-30+S60 were low, but already significantly greater than that of urea. After the middle growth stage, POCU-S60 was recovered higher than the others. The recoveries of POCU-S60 gradually increased from 55% of dissolved N during the middle growth stage to 72% at the harvest, where those of POCU-70 increased from 30 to 61%. At the end of the growing season, the recoveries of urea, POCU-70 and POCU-30+S60 were 51, 61 and 70%, respectively. The significant difference in years and the interaction among the N source and year were caused by the low recovery of urea that appeared in 1995 due to normal rainfall. The better synchronization between the N dissolution from POCU-S60 and N requirement by corn would increase the recovery of the POCU-30+S60 treatment and contribute to the lower susceptibility to yearly variations in climate.
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