Precision Fertigation for Specialty Crops.

Advances in micro irrigation have facilitated greater adoption of fertigation for specialty crops. Fertigation improves nutrient uptake efficiency, minimize leaching of NO₃-N below the root zone, and increases the yield and quality as compared to those with dry fertilizer broadcast. This paper is based fertigation research conducted on citrus and potatoes. Two-year studies on newly planted citrus trees showed no significant difference between the fertigation and dry fertilizer broadcast treatments. Conditioning the trees with different nutrient management programs since the planting and evaluation done during the seven and eight-year old trees showed significantly greater fruit yield with fertigation as compared to that with dry granular fertilizer broadcast. The optimum N rate for the former was lower by 35 kg^.ha^-1 as compared with the latter. ‘Hamlin’ orange trees on ‘Cleopatra mandarin’ rootstock showed no difference between the fertigation and dry fertilizer broadcast, except at high N rate. Thirty-five plus year old ‘Valencia’ orange trees on ‘Rough lemon’ rootstock showed a significant decrease in surficial aquifer NO₃-N concentration underneath a grove which received total fertigation as compared to dry granular  broadcast (3 appl/year) of similar N rates. In-season fertigation is necessary for Potato production in sandy soils to supply adequate availability of N to satisfy the crop requirement and minimize leaching losses. For high-production potential of up to 70-80 Mg/ha high-processing quality potatoes, about 280-330 kg/ha N is required with 1/3 applied at pre-plant and remaining 2/3 as in-season fertigation using urea ammonium nitrate (UAN, 32% N). In-season N is delivered in five fertigations at 2-week intervals, 3-4 weeks after seedling emergence. Increasing the frequency of fertigation to 10 to 20 during in-season failed to show any beneficial advantages in terms of total and different size grade tubers.