Increasing Yield; of the Second Crop Rice with Improvement of Fertilizer Efficiency and Sail Nitrogen Fertility

USG深施提高氮素回收率及稻谷產量之效果，以一期稻優於二期稻，一期稻谷增產量可達13%，氮回收率最高可達77%；二期稻谷增產量最高僅有3%（屏東新埤），而氮回收率最高亦只有41%。 二期作USG深施在含有膨脹性粘土礦物之臺中土壤其稻谷增產量最高可達18%，氮肥同收率在30%～71%之間，皆優於不含膨脹性粘土礦物之屏東新埤試區，後者稻谷增產為3%，及氮肥回收率在8%～41%之間。 施用稻穀亦可提高氮肥回收率，同時增加植體氮鉀含量因而提高稻谷產量，二期作施用之效益，平均增加谷產量8%，大於一期作之增加4%。彰化竹塘一期作加施稻殼者，紋枯病減輕，而谷產量可增加9%以上。 屏東新埤試區無論一、二期水稻施用爐渣後，谷產量有顯著下降之現象，而臺中、彰化兩試區有增產之趨勢。 Increase of N recovery % and grain yield upon USG deep placement, the first rice crop was superior than the second rice crop. For the first rice crop, grain yield increased up to 13%, while N recovery increased up to 77%. However, it was found grain yield of the second rice crop only increased about 3% at Pingtung Experiment Site, while the N recovery rate increased about 41%, lower than that of the first crop by 36%. The effect of USG deep placement on grain yield and N recovery rate may be relatedto existing of expanding clay minerals in soils. As higher amount of expanding clay minerals in Taichung soil, grain yield increased by 18% and N recovery rate increased from 30% to 71%. At Pintung Experiment Site, the soil contains no expanding clay minerals, grain yield only increased by 3% and N recovery rate also increase from 8% to 41%. Increasing the fertilizer efficiency of USG deep placement may be partly attributed to the higher ammonium adaptive nature due to the existence of expanding clay minerals in soils This may explain why higher N recovery rate of USG deep placement at Taichung site and lower at Pingtung site Application of rice husk increased not only withe increasing N recovery rate but also increased with uptake of N and K by rice plant. As respond to the grain yield, it increased about 9% for the second rice crop, and 4% for the first rice crop in general. The use of rice husk also depressed banded sclerotial disease of rice plant which in turn increased grain yield by 9% at Changhua Site. Based on our results, response of grain yield increase by application of rice husk was much significant than the use of slag. In Pingtung, use of slag even caused slightly yield decline. But with use of slag combined with rice husk, it significantly reduced the tendency of grain yield decline