Effect of land management on soil microbial N supply to crop N uptake in a dry tropical cropland in Tanzania

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• 作者：Soh  ; Sugihara^a ;   ; ^{sohs@kais.kyoto-u.ac.jp} ; Shinya  ; Funakawa^a ; Method  ; Kilasara^b ; Takashi  ; Kosaki^c
• 关键词：Microbial biomass N ; Microbial C ; N ratio ; Soil-crop N dynamics ; Land management ; Dry tropical cropland ; Sub-Saharan Africa
• 刊名：Agriculture, Ecosystems & Environment
• 出版年：2012
• 出版时间：1 January 2012
• 年：2012
• 卷：146
• 期：1
• 页码：209-219
• 全文大小：1183 K

文摘

In Sub-Saharan Africa, conservation of available soil N during early crop growth, when N loss by leaching generally occurs, is important to improve crop productivity. In a dry tropical cropland in Tanzania, we assessed the potential role of soil microbes as a temporal N sink¨Csource to conserve the available soil N until later crop growth, which generally requires substantial crop N uptake. We evaluated the effect of land management [i.e., no input, plant residue application before planting (P plot) with or without fertilizer application, fertilizer application alone, and non-cultivated plots] on the relationship between soil N pool [microbial biomass N (MBN) and inorganic N] and crop N uptake throughout the ?20-d crop growth period in two consecutive years. In the P plot, MBN clearly increased (?4.6?9.6 kg N ha^?) early in the crop growth period in both years because of immobilization of potentially leachable N, and it conserved a larger soil N pool (?0.5?1.2 kg N ha^?) than in the control plot. Especially in one year in which N leaching was critical, increased MBN maintained a larger soil N pool in the P plot throughout the experimental period, and a delay of increased MB C:N ratio and a substantial decrease in MBN was observed, indicating better soil microbial N supply for crop N uptake during later crop growth. Therefore, plant residue application before planting should enhance the role of soil microbes as a temporal N sink¨Csource, leading to the conservation of potentially leachable N until later phase of crop growth, especially in years in which N leaching is relatively severe. Although further studies are necessary, our results suggest that plant residue application before planting is a promising option to achieve better N synchronization.