Effects of Irrigation Regimes, Planting Dates, Nitrogen Levels, and Row Spacing on Safflower Cultivars

Information was needed on application time and amount of irrigation water, date of planting, row spacing, and nitrogen fertilizer rates on cultivars of safflower(Carthamus tinctarius L.). The objective was to develop a more efficient management of the crop. The environments of growth listed above were studied in three experiments over a 3-year period. In each experiment date of planting was the large plot with irrigation treatments in border-diked basins as split plots followed by other environnients in the basins as subplots. In 2 of the 3 years, seed yields were higher in the crop planted 15 December than in that planted 15 February; results were the opposite in the first year because of rank growth due to lower-than-average temperatures. An irrigation regime that specified an earlier cutoff date than that for the normal regime saved water and labor, reduced weed growth, and produced optimum seed yields at lower levels of nitrogen fertilization. Other irrigation treatments that limited the amount of water below that of the normal regime (102 to 120 cm), either gave equivocal results or significantly reduced yields. Oil percentage 01 seed was not affected by irrigation regimes. Plants in two-row plots produced fewer seeds∕head and smaller seeds than those in one-row plots. The increased plant populations in the two-row compensated for these deficiencies and yields were no different. The optimum level of N fertilization ranged from 84 to 336 kg/ha, depending on date of planting, irrigation regime, and cultivar. For a Laveen clay loam soil (coarseloamy, mixed, hyperthermic, Typic Calciorthid), 168 kg/ha of N was apparently optimum when the crop was planted in December. More than 84 kg/ha, however, produced no yield advantage when the crop was planted two months later. The cultivar ‘Dart’ outyielded ‘Rio’ and ‘Prio’ in 1969, ‘12289’ and ‘US 10’ in 1970, and ‘14154–30’ and ‘PI 209,285’ in 1972. Differences in days to flower and duration of flowering were significantly correlated with seed yield, but the correlations were low. Neither flowering time nor duration affected oil content of the seed.