Nitrogen Rates and Harvesting Time Influence Nitrate
Accumulation by Chinese Cabbage. (S04-wang891334-oral)
Authors:
Z. Wang* - Southwest Agri. Univ.
H. Li - Southwest Agri. Univ.
B. Li - Southwest Agri. Univ.
X. Yei - Southwest Agri. Univ.
P. Sun - Chongqing Agricultural Bureau T. Xiang - Chongqing Agricultural Bureau H. Dai - Chongqing Agricultural Bureau C. Tu - NC State Univ.
Abstract:
Nitrogen (N) rates and harvesting time greatly influence the nitrate accumulation and quality of leafy vegetables. A field experiment was carried out to examine these issues on high- and low- fertility soils in Chonqing, southwest China. Chinese cabbage biomass was significantly quadratically correlated with N rates for different harvesting times. The maximum plant yields could be obtained at the N rate of 225 kg•ha-1 on two soils, while the optimum yields at the 150 kg N•ha-1. In the controls, average plant nitrate contents were 2160±728 mg•kg-1 and 1049±779 mg•kg-1 in high- and low-fertility soils, respectively. Nitrogen application increased the plant nitrate content by 23.5~30.1% in high fertility soil, and 140.5~185.1% in low fertility soil. The plant nitrate accumulation significantly linearly increased with harvest time in both soils. The nitrate accumulation rates (ratios of plant nitrate to growth days) were 2.21~3.49 times greater in high- than in low- fertility soil. The maximum nitrate accumulation by plants occurred in the 225 kg N•ha-1 at the 40th and 45th day of transplanting for high and low fertility soils, respectively. Two-day continuous sunshining decreased plant nitrate content by 10.5%~25.2%. In addition, the contents of vitamin C, soluble sugar and amino acids in plants were considerably increased by deferred harvesting, but decreased by N application.
Speaker Information: Zheng-yin Wang, Southwest Agri. Univ., College of Resources and Environmental Sciences, S, Chongqing, 400716; Phone: (+86)-23-6825-1825; E-mail: [email protected]
Session Information: Thursday, November 6, 2003, 8:40 AM-10:30 AM Presentation Start: 9:00 AM
Keywords: Nitrogen rate; Harvesting time; Nitrate accumulation; Soil fertility