Dynamics of microbial biomass nitrogen in relation to plant nitrogen uptake during the crop growth period in a dry tropical cropland in Tanzania
Version of Record online: 1 MAR 2010
© 2010 Japanese Society of Soil Science and Plant Nutrition
Soil Science & Plant Nutrition
Volume 56, Issue 1, pages 105–114, February 2010
How to Cite
SUGIHARA, S., FUNAKAWA, S., KILASARA, M. and KOSAKI, T. (2010), Dynamics of microbial biomass nitrogen in relation to plant nitrogen uptake during the crop growth period in a dry tropical cropland in Tanzania. Soil Science & Plant Nutrition, 56: 105–114. doi: 10.1111/j.1747-0765.2009.00428.x
- Issue online: 1 MAR 2010
- Version of Record online: 1 MAR 2010
- Received 11 May 2009. Accepted for publication 27 October 2009.
- microbial biomass carbon;
- microbial biomass nitrogen;
- microbial respiration;
- soil–plant nitrogen dynamics;
- tropical cropland
Soil microbes are considered to be an important N pool in dry tropical croplands, which are nutrient poor. To evaluate the N contribution of soil microbes to plant growth in a dry tropical cropland, we conducted a maize cultivation experiment in Tanzania using different land management treatments (no input, plant residue application, fertilizer application, plant residue and fertilizer application, and non-cultivated plots). Over 104 experimental days, we periodically evaluated the microbial biomass N and C, plant N uptake, microbial respiration in situ and inorganic N in the soil. A significant amount of inorganic N was lost in all of the treatment plots as a result of leaching during the initial 60 days and inorganic N remained low thereafter (∼20–35 kg N ha−1 : 0–15 cm), whereas soil microbial respiration substantially decreased because of soil drying after 60 days (grain-forming stage). During the grain-forming stage (60–104 days), we found a distinct effect of plant N uptake on soil microbial dynamics, although we did not observe an obvious effect of plant residue and/or fertilizer application; microbial biomass N decreased drastically from 63–71 to 18–33 kg N ha−1 and the microbial biomass C : N ratio simultaneously increased (>10-fold) in all maize-cultivated plots; these features were not observed in the non-cultivated plot. Plant N uptake over the same period was 26.6–55.2 kg N ha−1, which was roughly consistent with the decrease in microbial biomass N. These results indicate that strong competition for N occurred between soil microbes and plants over this period and N uptake by plants prevented microbial growth. Thus, we concluded that soil microbes contribute to plant growth by serving as a N source during the grain-forming stage in dry tropical cropland.