Effects of planting dates and spacing on several characteristics of short day onion varieties grown in South Texas

Abstract

The effect of planting dates and spacings on several characteristics of short-day onion varieties were investigated. In 1984/85 experiments, three varieties, Special 38, Asgrow 429, and Texas Grano 1015Y produced significantly better yields than the rest of the varieties. In 1985/86 experiments, variety Texas Grano 1015Y was the top yielding, and significantly differed from the rest. When all varieties were combined, better yields were obtained in plots planted on October 12, and November 16, for the 1984/85 experiments, and September 17, for the 1985/86 experiments. However, each variety produced better yields when associated to a specific planting date. Spacing also had an important influence on several onion characteristics. When the number of rows/bed was increased from 2 to 6, yields and L/D ratio significantly increased, while percentage of doubling bulbs, percentage of seed stems, bulb length, bulb diameter, and bulb weight significantly decreased. There was no significant increase of yield when spacing was changed from 4 to 6 rows/bed, but there was significant decrease of bulb size when spacing was changed from 4 to 6 rows/bed. Consequently, the use of four rows/bed to achieve better yields of better quality bulbs would be suggested. In addition, the effect of the position of the rows within each spacing was studied. Southmost rows of plots planted with 4 rows/bed (spacing 2) and 6 rows/bed (spacing 3) consistently produced significantly higher yield of marketable and total bulbs of larger diameter, larger length, higher weight, higher percentage of doubling, lower percentage of seed stems, and smaller L/D ratio. Finally, based on these results, it was shown that it would be possible and profitable to harvest onions in the Texas Rio Grande Valley from March 20, to May 20, if the varieties TG 1015Y, TG 1025Y, TG 1030Y, TG 1105Y, Asgrow Y33, and Asgrow 429 were used in planting dates from September 17, to November 14, from which yields were always over 40t/ha.