1. National Engineering Laboratory for Improving Quality of Arable Land; Inst. of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences; Beijing 100081 China
2. Qiyang Agro-ecosystem of National Field Experimental Station; Hunan 426182 China
3. USDA; Agricultural Research Service San Joaquin Valley Agricultural Sciences Center; Parlier CA 93648-9757
4. Dep. of Plant Sciences; Univ. of California; Davis CA 95616-5270 USA