Spring-summer tomato yield as a function of potassium fertilization in field and protected crops

Abstract

Off-season tomatoes produced in Southeast Brazil in Spring-Summer crops are highly valued, but crop yield is limited by high rainfall and temperatures. To overcome this situation and make off-season tomato crops more profitable, they can be grown under controlled conditions in protected cultivation systems. In addition, tomato yield and quality can be improved by adequate levels of potassium (K) fertilization. The present study evaluated the off-season (Spring-Summer) yield of tomato crops grown in the field or in protected systems (hydroponics and fertigation) using different levels of K application. Tomato plants (hybrid Saladinha) were simultaneously grown under the 3 systems from September 2005 to February 2006 (2005 off-season) and from July to November 2006 (2006 off-season) in Seropédica, RJ, Brazil. In 2005, four nitrogen:potassium (N:K) ratios were tested, and in 2006 two levels of K supply were evaluated. In 2005, marketable fruit yield was lower in the field and similar in the hydroponics and fertigation systems, without consistent effects of N:K ratios on tomato yield. In 2006, when a higher level of fruit yield was achieved, the hydroponic system yielded more marketable tomatoes than fertigation and field systems. In 2006, the higher K level stimulated the shoot growth in the three systems and increased by 11% the marketable fruit yield in the average of the three systems, indicating that increased K supplies are required to improve tomato growth and yield in protected crops.