Potassium Management for Improving Processing Tomato Yield and Quality in Xinjiang

The objectives of this study are to determine the appropriate ratio of K sources applied in fall by evaluating the yield/quality of drip-irrigated processing tomato, and Cl^- residue in the soil profile.

The split application of KCl alone or combined with K₂SO₄ produced more fruit yield than when all of the KCl was applied basally in the fall. Application of 50% of the K as KCl after flowering resulted in more agronomic efficiency (AE), more profit and higher value-to-cost ratio (VCR) than the treatment with 50% of the K recommendation as K₂SO₄ after flowering. Application 50% of the K as K₂SO₄ at flowering and fruiting stage resulted in higher total acid, color difference and lycopene content than application of KCl alone.

Later application of K fertilizer increased K accumulation by tomato plants. Application of 50% of the K as KCl basally in fall plus the remaining K as K₂SO₄ at flowering and fruiting stages resulted in more plant K accumulation than treatments providing 100% of the K basally in the fall as KCl. Combined application of KCl and K₂SO₄ decreased the Cl^- concentration in plant tissues and the total plant accumulation of Cl^-, resulting in a less residual Cl^- in the tomato fields compared with application of KCl alone. When only KCl was applied, basal application of 100% of the K had a lower Cl^- content at the soil surface (0 to 20 cm), but had a higher Cl^- level at depth (40 to 80 cm) than treatments providing 50% or 100% of the K at later stages. More KCl applied in later stages resulted in higher the Cl^- concentrations in the soil surface layer. Combined application of KCl and K₂SO₄ resulted in lower Cl^- at the soil surface (0 to 40 cm) than treatments with KCl alone.

It was concluded that the best K management practice in drip-irrigated processing tomato production in Xinjiang was to apply 50% of the K requirement as KCl basally in the fall combined with the remaining K as K₂SO₄ at flowering and fruiting stages.