Comparative study of nitrogen budget in three different vegetable planting patterns under greenhouse condition

Nitrogen use efficiency reflects the amount of N assimilation of crops, which is a critical for agricultural production. Unreasonable N application and excessive fertilizer-N input have frequently resulted in soil compaction, groundwater pollution and low quality crop products. This has received a considerable researcher and consumer attention in recent years. A simple formula introduced in this study to determine apparent nitrogen budget (ANB) was as follows: ANB = NI NO, NI is N input and NO is N output. Data from a long-term field experiment initiated in 2002 at the Quzhou Agricultural Experimental Station were used to determine ANB under three planting patterns of vegetable. The planting patterns included organic pattern, low-input pattern and conventional pattern. The study aimed to provide reference materials for the development of a sustainable high-yield planting pattern. Based on the results, a significant difference was noted among soil total nitrogen content in 0 20 cm soil layer of the three planting patterns during the growth period of eggplants. The nitrogen contents in 0 20 cm soil layer of the organic, low-input and conventional patterns were 2.6 g·kg^-1, 1.7 g·kg^-1 and 1.3 g·kg^-1, respectively. Total nitrogen input in the organic, low-input and conventional patterns was 1 150 kg·hm^-2, 1 182 kg·hm^-2 and 1 433 kg·hm ^-2, respectively. The corresponding total nitrogen uptake by crops was 178 kg·hm^-2, 135 kg·hm^-2 and 116 kg·hm^-2, respectively. Also eggplant yield under the three cropping patterns in 2011 was 93 458 kg·hm^-2, 93 320 kg·hm^-2 and 90 209 kg·hm^-2, respectively. Net nitrogen surplus for the growth period of the eggplants was 971 kg·hm^-2, 1 046 kg·hm^-2 and 1 317 kg·hm^-2, respectively. The eggplant yield under organic pattern was respectively 0.1% and 3.6% higher than that under low-input and conventional patterns. Net nitrogen surplus under organic pattern was 7.2% and 26.3% lower than that under low-input and conventional patterns. From the above results, it was concluded that organic pattern was contributed the highest to soil N accumulation and had the highest yield and lowest net nitrogen surplus. This led to the highest nitrogen use efficiency when compared with the low-input and conventional patterns. The paper compared ANB in three different planting patterns of eggplants under greenhouse condition and contributed to sustainable and high-yield organic production practices in China.