ISSN 2756-3642
International Journal of Agricultural Extension and Rural Development ISSN 2756-3642 Vol. 11 (5), pp. 001-011, May, 2023. © International Scholars Journals
Full Length Research Paper
Nitrogen balance and dynamics as affected by water table and fertilization management in celery (Apium graveolens) cropping system of southwestern China
Huaming Guo 1, 2 * Guanghe Li 1, Dayi Zhang 1, Xu Zhang 1 and Chang’ai Lu3
1Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, P. R. China
2 Department of Water Resources and Environment, China University of Geosciences, Beijing 100083, P. R. China
3Chinese Academy of Agricultural Science, Beijing 100081, P.R. China
Accepted 15 February, 2023
Abstract
There is a great concern on N cycle and dynamics in intensive cropping agricultural ecosystems because of their possible negative environmental consequences. Field experiments were conduced at the Dianchi catchment, Yunnan, China, to investigate the combined effects of groundwater table and N fertilization rate on gaseous N emissions, N leaching, and soil N accumulation, together with N uptake by celery in order to establish a budget of N inputs and N outputs in closed greenhouses. Treatments consisted of a combination of two water table levels: one with a water table depth of 2.0 m BLS (Below Land Surface) (Site A) and the other with a water table depth of 0.5 m BLS (Site B), and three N fertilizer application rates: 0 kg N ha-1 (no fertilization - NF), 450 kg N ha-1 (low fertilization - LF) and 1200 kg N ha- 1(high fertilization - HF) per rotation (about 90 d). Outputs of N were mainly as N uptake, with an average of 53.9% of total estimated output N. Crop N uptake significantly increased with an increase of N rate, but further fertilizer N inputs beyond 450 kg N ha-1 did not lead to significant increases in N uptake. The same N-fertilizer application rate produced different N balances with different water table levels. Compared with Site B, Site A reduced N leaching, gaseous N emissions, and soil N accumulation, while increased N uptake. The N balances indicate that N leaching into groundwater was comparatively low, while gaseous N emissions were the major loss pathway in the celery (Apium graveolens) cropping system, although both N leaching and gaseous N emissions decreased with the decrease of N-fertilizer rate and the increase of water table depth. Of these gaseous N emissions, NO/NO2 was the highest, followed by N2O and NH3. In low N fertilization treatment, gaseous N emissions were reduced by 75 kg N ha-1, N leaching by 8.4 kg N ha-1, and soil N accumulation by 264 kg N ha-1 at Site A. Even LF had resulted in significant N losses at Site B. These findings suggest that the balanced fertilization both in optimizing crop yields and in minimizing its adverse impacts on environment should take into account depth of groundwater table.
Key words: Agricultural ecosystem, gaseous N emissions, N leaching.