Potassium Management for Improving Processing Tomato Yield and Quality in Xinjiang

Experiments were conducted in Xinjiang in 2012 to investigate the principles of biomass and K accumulation of processing tomato, determine the appropriate rate and time of K application, and study the effect of K source (KCl, K₂SO₄, and KNO₃) on fruit quality.

Dry matter accumulation increased rapidly 53 days after transplanting (DAT) when tomato fruits were growing rapidly. The portion of the fruit increased from 31% of total biomass at the fruit initiation stage (37 DAT) to 45% at the rapid expanding stage (53 DAT), and then to 68% at maturity. More dry matter accumulated when K was applied after flowering than when K was applied only basally.

Potassium accumulation increased rapidly after 37 DAT, earlier than dry matter accumulation. Potassium accumulated by stem and leaves remained stable after 37 DAT, and the K uptake in later stages of tomato growth was mainly transformed to the fruit. At 96 DAT, K uptake again increased with increased rate of K application, with more K getting accumulated when K was also applied at flowering and/or fruiting stage than only as basal application. The greatest accumulation of K occurred when one half of the recommended K (120 kg K₂O/ha) was applied at flowering and another half at fruiting stage. Therefore, sufficient K supply in later stages of tomato growth was important for biomass accumulation and K nutrition of processing tomato.

Rate and time of K application greatly influenced fruit yield. More fruit was obtained when K was applied in the later plant growth stages as compared to applying all K as basal application. Application of 120 kg K₂O/ha, with one half applied at flowering stage and the remaining half applied at fruiting stage, produced 3.4 to 12 t/ha more fruit and 268 to US$710 more benefit than other rates and times of K application studied.

At the rate of 120 kg K₂O/ha, K sources did not significantly affect fruit yield, but affected some indices of fruit quality. Potassium nitrate (KNO₃) resulted in higher vitamin C content than K₂SO₄ and KCl . Fruit color, β-Carotene, soluble solid, and lycopene contents were not affected by K sources. Application of KCl resulted in more fruit yield, higher agronomic efficiency, and more economic benefit than K₂SO₄ and KNO₃ applications. NW Tomato K