Over a period of two years , field experiments were conducted on four silty loam soils grown with foliar vegetable crops including Chinese cabbage (Brassica pekinensis Rupr., cv. Lu-Bai 3), autumn greens (B. chinensis L., cv. Piao-Geng-Bai), winter greens (B. var. rosularis Tsen et Lee, cv. You-Dong-Er), and summer greens (B. chinensis L., cv. Zao-Shu 5), respectively. Each experiment included one CK treatment without K, N and P fertilizers applied, and four treatments with from low to high doses, 0-300 kg hm-2 for Chinese cabbage, 0-150 kg hm-2 for autumn and winter greens and 0-180 kg hm-2 for summer greens, of K fertilizers in the form of sulfate of potash (SOP) applied together with N and P fertilizers. One treatment of K fertilizer in the form of muriate of potash (MOP) applied at high levels (150 or 180 kg hm-2) together with N and P fertilizers was included in the experiments of autumn, winter and summer greens , respectively, in order to compare the effects of SOP and MOP. The market yields of the tested crops increased significantly with the increasing rate of K application. The crops supplied with K fertilizers yielded more stably as the CV% of their yields decreased with the rate of K application. K fertilization increased not only K contents but also the amounts of N, P and K absorbed in shoots of autumn, winter and summer greens, which were statistically significantly correlated to their yields. It can also be found that potassium improved the quality of the foliar vegetable crops as their dry mater contents were generally increased and Vc contents obviously increased and nitrate contents markedly decreased. As compared to MOP, SOP was more effective on the yields and quality of autumn, winter and summer greens at the high levels of fertilization.
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机译：Over a period of two years, field experiments were conducted on foursilty loam soils grown with foliar vegetable crops including Chinesecabbage ({ Brassica pekinensis Rupr., cv. Lu-Bai 3), autumngreens (B. chinensis L., cv. Piao-Geng-Bai), winter greens(B. var. rosularis Tsen et Lee, cv. You-Dong-Er), and summergreens (B. chinensis L., cv. Zao-Shu 5), respectively. Eachexperiment included one CK treatment without K, N and P fertilizersapplied, and four treatments with from low to high doses, 0300kg hm-2 for Chinese cabbage, 0150 kg hm-2 forautumn and winter greens and 0180 kg hm-2 for summergreens, of K fertilizers in the form of sulfate of potash (SOP) appliedtogether with N and P fertilizers. One treatment of K fertilizer in theform of muriate of potash (MOP) applied at high levels (150 or 180 kghm-2) together with N and P fertilizers was included in theexperiments of autumn, winter and summer greens, respectively, in orderto compare the effects of SOP and MOP. The market yields of the testedcrops increased significantly with the increasing rate of Kapplication. The crops supplied with K fertilizers yielded more stablyas the CV% of their yields decreased with the rate of K application. Kfertilization increased not only K contents but also the amounts of N,P and K absorbed in shoots of autumn, winter and summer greens, whichwere statistically significantly correlated to their yields. It canalso be found that potassium improved the quality of the foliarvegetable crops as their dry mater contents were generally increasedand Vc contents obviously increased and nitrate contents markedlydecreased. As compared to MOP, SOP was more effective on the yields andquality of autumn, winter and summer greens at the high levels offertilization.
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