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An epidemiological investigation was conducted in the Amami Islands of Kagoshima Prefecture, Japan, to determine the pathogenesis of citrus greening disease, also known as citrus Huanglongbing (HLB) disease, especially in relation to trace metal nutrition. We sampled 11 sites with acidic soil and 46 sites with alkaline soil in private gardens on the islands of Tokunoshima and Amami Oshima. At the acidic sites, no HLB-infected citrus trees were detected using PCR amplification. In the private gardens, 38.6% of the trees tested were infected with HLB disease. By comparing soil pH values in those private gardens, we found that HLB infection was related to soil pH. Among trees growing in alkaline soil, 47.8% were infected, whereas none of the trees growing in acidic soil in the private gardens were infected. When comparing a distribution map of HLB-diseased trees with a soil component map of the five Amami Islands, HLB disease was not detected in acidic soil, but the distribution of HLB-diseased trees was similar to the location of alkaline soil. Microelement analysis of leaves from trees grown in alkaline soil revealed significantly lower levels of manganese (71.9%), copper (70.1%), zinc (52.3%), and iron (40.9%) compared with the leaves from trees grown in acidic soil. These results suggest that HLB disease prefers citrus growing in alkaline soil where the concentrations of Fe and Zn nutrients are reduced.

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The objectives of this study were to produce ISN-iabeled poultry manure compost, evaluate the uniformity of lsN labeling of poultry manure and investigate the ISN recovery derived from ISN-iabeled feed during the production of lsN-labeled poultry manure compost. Eight chicken layers were fed with lsN-labeled feed containing 2.57 atom% lsN excess for 22 d, and then with unlabeled feed for 6 d. The feces were collected during a period of 28 d. The collected fresh feces were respectively dried, smashed, and all the collected feces were mixed thoroughly. The ISN abundance of the prepared ISN-iabeled poultry feces (abb. PLPF) was 1.69 atom% lsN excess. The recovery of lsN derived from ISN-iabeled feed was 41.2% after feeding to chicken layers. The ISN abundance in the major fractions of the PLPF separated by the method of Yonebayashi and Hattori (Soil. Sci. Plant Nutr., 26, 469-481, 1980), was not significantly different except for the amide-N fraction. Since the rate of amide-N fraction to total manure N was very low, it was considered that the PLPF obtained by this method would be suitable for studying the dynamics of manure N used as soil amendment. The recovery of ISN derived from lsN-labeled feed was 12.1% after composting. About 70% of total manure N was lost during composting. The major N loss from poultry manure during composting was due to ammonia volatilization.