Nutrient Management Research Database

Trickle irrigation in combination with feedback from in-season nitrogen (N) tissue tests offers almost unlimited flexibilty in developing site-specific nutrient management plans. Field experiments were conducted during1994-95 in southern Arizona to evaluate the agronomic, economic, and environmental response of broccoli and cauliflower to a factorial arrangement of water and N rates, both ranging from deficient to supra-optimal. Concurrent evaluation of crop response surfaces for marketable yield, net economic return,and unaccounted for nitrogen fertilizer determined that profitable yields of broccoli and cauliflower could be produced with minimal impact on the environment

Combining drip irrigation and in-season tissue nitrate tests allows for effective adjustment of fertilization rates in-season. This study focused on broccoli and cauliflower.

This study sought to 1) develop N tissue tests to monitor plant N levels and properly adjust fertilizer rates and timing and 2) to identify the response of broccoli and cauliflower to adjustments in N and water applications in order to construct best management practices recommendations.

Three rates of water and three rate of nitrogen were applied at all possible combinations. Nitrogen rates were 89, 178 and 267 lbs N/ac and water was applied at levels determined to be dry, optimum, and excess. Water and fertilizer wre appleid via a subsurface drip irrigation system.

Yield

Nitrogen deficiency had a more pronounced detrimental effect on marketable yield as compared to the excess water conditions. N deficiency at the 89 lbs N/ac rate decreased broccoli yields by 50% and cauliflower yields by 85%.

Water deficiency was not observed to the high rainfall during the study period. Excess water decreased yields by 14 and 32% for broccoli and cauliflower respectively.

Harvest Quality

Quality of both crops were decreased with nitrogen deficiency.

Nitrogen Loss

Nitrogen losses exceeded 100 lbs/acre when 267 lbs N/ac was applied with excess water rates.

Best Management Practices

Results from tissue testing indicated optimal cumulative rates of 219 lbs N/ac for broccoli and 260 lbs N/ac for cauliflower