Multi-objective water-nitrogen regime optimization to enhance yield, quality and productivity of drip-fertigated greenhouse tomato in northwest China

Summary

This two-season split-plot field experiment in northwest China examined water–nitrogen interactions in drip-fertigated greenhouse tomato under arid conditions. Increasing irrigation from 50% to 100% crop evapotranspiration raised yield by 80% and nitrogen uptake by 39%, but reduced fruit quality (total soluble solids and sugars by 12–28%) and water productivity. Similarly, raising nitrogen from 0 to 250 kg ha⁻¹ boosted yield, quality and nutrient yield, but further increases (350 kg ha⁻¹) proved counterproductive. Multi-objective optimisation identified 100% ETc combined with 250 kg N ha⁻¹ as the most balanced regime, maximising economic return whilst maintaining both quality and resource efficiency.

Regional applicability

The findings are directly applicable to protected horticulture in water-scarce and nitrogen-limited regions of the United Kingdom, particularly during periods of drought stress or in regions adopting intensive greenhouse production. However, the specific irrigation and nitrogen rates optimised for northwest China's arid climate and soils may require recalibration for UK conditions, which typically have higher rainfall and different soil types; the methodological approach and multi-objective optimisation framework remain highly transferable.

Key measures

Fruit yield (FY), nitrogen uptake (NU), total soluble solids (TSS), soluble sugars (SS), titratable acid (TA), nitrogen use efficiency (NUE), water productivity (WP), nutrient water productivity (NWP(TSS) and NWP(TA)), economic return, and TOPSIS multi-criteria evaluation score

Outcomes reported

The study evaluated the effects of four irrigation levels (50–125% crop evapotranspiration) combined with four nitrogen rates (0–350 kg ha⁻¹) on fruit yield, quality, nitrogen uptake, nutrient yield, and water-nitrogen productivity in drip-fertigated greenhouse tomatoes. Multi-objective optimisation identified W3N3 (100% ETc and 250 kg N ha⁻¹) as the best balance between yield, fruit quality, nutrient yield and resource productivity.

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