Effects of different potassium sources on yield, quality and net income of processing tomato

Case study
Processing tomato requires large quantity of K, more than N, to meet healthy growth and to acquire high yield and quality product. In production, growers usually use potassium sulfate (K₂SO₄) or potassium nitrate (KNO₃) as K sources rather than potassium chloride (KCl), because most of them fear that KCl could be detrimental to tomato yield and quality, especially in the arid regions. Chapagain et al. (2003) reported that using part or full rate KCl to substitute for KNO₃ in fertigation did not affect growth and yield of processing tomato. Further, they found that compared to KNO₃, KCl treatments improved tomato quality such as increased fruit hardness and green calyces attached, and decreased percentage of fruit decay as well. In an experiment that compared effect of KCl and K₂SO₄ on tomato growth, Zhang et al. (2008) demonstrated that use of KCl in Xinjiang increased tomato yield by 7.0%－9.2%. Wang et al. (2016) compared effects of the three K sources via fertigation under plastic mulch on yield, quality and economic returns of two processing tomato cultivars through field experiments (Table 1). The results clearly show that KCl much produced higher tomato yields than the other two K sources. The yield difference between the three K sources did not significantly differ for cultivar HYH-01 but did for cultivar Tunhe 8. There were no differences observed in tomato quality except that KCl increased Vc for HYH-01 (the other quality traits not shown here). Furthermore, applications of KCl considerably increased net income and agronomic efficiency of K fertilizers as well. Thus, KCl has proved to be a good K source as K₂SO₄ or KNO₃ for tomato production even in the arid region.

Table 1. Effects of different K sources on yield, quality and net income of processing tomato

Cultivar	Treatment	Yield (t/ha)	Yield increase (%)	Vc (mg/100g)	Profit ($US/ha)	AE (kg/kg)
HYH-01	K-0	90.28 b	-	27.53 b	2616.20	-
	KCl	120.18 a	24.87	28.40 b	3474.27	249.05
	K2SO4	114.88 ab	21.40	32.60 a	3308.00	204.83
	KNO3	110.35 ab	18.17	27.00 b	3166.07	167.10
Tunhe 8	K-0	74.74c	-	27.97 a	2128.73	-
	KCl	92.46a	19.17	30.63 a	2605.67	147.70
	K2SO4	83.49b	10.49	29.63 a	2324.73	72.98
	KNO3	87.36ab	14.44	24.13 a	2445.60	105.14

References:

Chapagain B.P., Wiesman Z., Zaccai M., et al. 2003. J. Plant Nutr., 26(3):643–658.

Zhang, Y., Ma, H.G., Xu W.L., Wang H.Y., Qi G.H., Yang L.C. 2008. Soil and Fertilizer Sciences in China, 3:40–51.

Wang J.X., Li Q.J., Zhang Y. 2016. pp. 94 in Proceedings of the international symposium on improvement of nutrient use efficiency under zero growth of chemical fertilizers in China, March 16-18, 2016, Beijing.