Drip fertigation promotes water and nitrogen use efficiency and yield stability through improved root growth for tomatoes in plastic greenhouse production

Abstract

Drip fertigation increases water and nitrogen use efficiency, and reduces nitrogen leaching in comparison to conventional flood irrigation and over fertilization in plastic greenhouse vegetable production. However, it is unknown whether this also improves yield stability, possibly through improved root growth. A two-factor field trial was conducted in a randomized block experimental design with drip vs. flood fertigation and with vs. without straw application over eleven growing seasons for six years with following treatments: (i) flood irrigation with over fertilization (conventional practice, hereafter CIF); (ii) CIF + Straw; (iii) drip fertigation with reduced irrigation and fertilization (hereafter DIF); (iv) DIF + Straw. The CIF treatments had application rates of 600 mm + 900 kg N ha−1 season−1 and DIF had 300 mm + 200 kg N ha−1 season−1. The ingrowth core method was used to measure root-growth characteristics, including root dry weight, root length density and specific root length. The water and nitrogen use efficiency and the inter-annual variation coefficient of tomato yield were also measured and calculated. There was no significant effect of straw on any of the variables measured, but there were significant differences related to CIF and DIF treatments. DIF had 101 % higher water use efficiency (p < 0.05; 25 kg m−3) and 296 % higher partial nitrogen fertilizer productivity (p < 0.05; 423 kg kg-1 N) in comparison to CIF. Furthermore, the inter-annual coefficient of variation in tomato yield was less in the DIF treatment by 18 %. Root dry weight (+31 %) and root length density (+34 %) for the DIF treatment were significantly higher for the 0−30 cm depth as compared to the CIF treatment, but lower at 30−50 cm depth (7 % and 11 %, respectively). Compared with autumn-winter growing season, winter-spring season significantly increased root dry weight and tomato yield and reduced inter-annual variation coefficient of yield (p < 0.05), and meanwhile the treatments did not significantly affect these seasonal differences. Our results highlight that drip fertigation improves the resource use efficiency and production stability due to the promotion of better root growth in plastic shed vegetable production regardless of growing season, and is therefore a more sustainable and effective technology of saving water and reducing risk of environment pollution.