Effects of irrigation and nitrogen on cauliflower development, yield and quality

Graduation date: 1993Field experiments were conducted with cauliflower (Brassica oleracea var.\ud botrytis cv. Snowball Y ) to determine crop development, yield, quality and\ud maturity response to various seasonal water levels, and to specific water stress\ud timing in relation to curd initiation. The effects of nitrogen rate, timing, and\ud source and the application of boron were also evaluated. Response parameters\ud included: total and marketable yield, head size and external appearance, internal\ud head solidity and discoloration, earliness, tissue nitrogen and boron uptake and\ud curd initiation effects.\ud Highest total and marketable yields occurred when soil moisture remained\ud above 50% of available water and replacement of evapotranspiration loss was at\ud least 90% during the post-initiation period. Early periods of water stress delayed\ud curd initiation but did not affect other parameters. Low water levels after curd\ud initiation advanced maturity and reduced leaf nitrogen levels. Higher water levels\ud delayed maturity, improved head size and external quality, but decreased internal\ud quality.\ud Total and marketable yields were not increased above 168 kg/ha applied\ud nitrogen. Response was optimum when splitting application rates between early\ud and late post-initiation timings and at high water levels, vs. early or late timings\ud alone. External quality and head size were improved and internal quality\ud declined above 56 kg/ha applied nitrogen. Water and nitrogen interacted to\ud enhance this effect. The lowest level of applied nitrogen (56 kg/ha) advanced\ud harvest, particularly under intensive irrigation; other nitrogen rate and timings\ud had no effect on maturity. Nitrogen rate interacted with water to influence leaf\ud nitrogen concentration, with low rates and high water levels reducing\ud concentration, and higher rates increasing it. Ammonium nitrate increased severe\ud hollowness when compared to calcium nitrate, but nitrogen source had no other\ud effects.\ud Applied boron increased leaf boron levels but did not affect other\ud parameters. Internal solidity increased with each successive harvest