Optimization of water and fertilization management parameters for winter-spring tomato under greenhouse drip irrigation condition

Objectives Drip irrigation is a valuable technology in intensive tomato production. Reasonable water and fertilizer management is the key measurement for the highest benefits. This study was attempted to build feasible parameters specified for the chosen tomato cultivar.

Methods A plot experiment was conducted inside a greenhouse using tomato cultivar RZ1404 as tested material during winter-spring season. Drip irrigation was used for watering and full water soluble fertilizers were applied with watering. Three water amounts (W1, W2 and W3) and 3 fertilizer rates (F1, F2 and F3) were designed, among which W2 and F2 were validated in the former researches as the relatively reasonable water and fertilizer amounts for tomato production. Soil water in-suit monitoring equipment was installed to collect soil water contents hourly at 0–100 cm depth in all 3 water levels under F2.

Results 1) With the increase of drip irrigation amounts, the yield, the nutrient uptakes and soil water contents were significantly increased, while the fruit qualities and the soil residual nutrients were significantly decreased. Compared with W1, the yields were increased by 6.8%–12.0%, the single fruit weights by 6.8%–8.6%, and the N, P₂O₅ and K₂O uptakes by 5.9%–11.7%, 8.9%–20.3% and 8.0%–8.3%, respectively, and the soil volumetric water contents were increased by 3.5–5.9 percentage points at 0–40 cm depth in W2 and W3. However, the fruit Vc and soluble solid contents were decreased by 4.6%–17.0% and 5.4%–9.7% in W2 and W3, respectively. The soil residual NO₃^–-N contents were decreased by 17.4%–37.6% at 0–40 cm depth, the Olsen-P contents were decreased by 16.5%–26.2% at 0–20 cm depth but increased by 5.0%–32.0% at 20–40 cm soil depth in W2 and W3. 2) With the increase of fertilizer amounts, the yields were increased slightly, and the nutrient uptakes and the soil nutrients accumulations were increased significantly. The nitrate, titratable acid, Vc, soluble solids contents in fruits were not changed obviously among all the 3 fertilization treatments. Compared with F1, the yield increases of F2 and F3 were not significant, and the N, P₂O₅ and K₂O uptakes were significantly increased by 6.0%–14.7%, 7.5%–15.7% and 11.9%–19.7%, respectively. Compared with F₁, the soil residual NO₃^–-N contents were increased by 71.7%–218.9% at 0–40 cm soil depth, the Olsen-P and readily available K contents by 28.9%–57.6% and 0.9%–11.3% at 0–40 cm soil depth in F2 and F3. 3) The W2F1 was recommended to drip irrigated tomato because of the relatively higher yield and fruit qualities, and lower residual soil nutrients. If only considering yield, the W3F3 would be recommended.

Conclusions Under the experimental condition, it is reasonable to keep the soil relative water contents of 69%, 78%, 78%, 87% and 87% during the setting of the first, second, third, fourth and fifth fruit cluster, respectively, when the fifth fruit cluster is expanding to 3–4 cm, 6–7 cm in diameter and harvesting, it is reasonable to keep the soil relative water contents of 87%, 69% and 56%, respectively. The lower limit of the soil relative water contents should be controlled at 62%, 67%, 67%, 77%, 77%, 77%, 62% and 50%, respectively. According to the above water criteria and dripping frequency of every 10–12 days, the recommended combination of water volumes (m³/hm²) and the formula fertilizers (N–P₂O₅–K₂O=22–12–16 for the seedling to flowering stages and 19–6–25 for the fruiting stage, kg/hm²) are 90/37.5, 195/75, 195/75, 270/(75–150), 270/(75–150), 270/(75–150), 195/75 and 120/75 in turn. Companied with basal application of commercial organic manure 22.5 t/hm² (N–P₂O₅–K₂O=1.50%–0.83%–1.76%, fresh weight), a target tomato yield of 140–150 t/hm² could be guaranteed.