Nutrient Rates and Placement

    Fertilizer applications should be based on crop nutrient demands and stage of crop growth. Tissue and soil analysis help to determine how much fertilizer to apply to complement the nutrient levels already available in the soil. Soil samples should be taken and appropriate fertilizers added as recommended by University of Hawaii soil scientists for the particular soil type. If the soil series is not known, growers should supply ample information about the origin of the soil sample so that the soil series can be determined through soil survey maps. Excessive fertilizer rates beyond crop needs may result in salt buildup, phytotoxic effects on plant growth, ground water contamination, delayed harvest due to excessive foliage growth, and capital losses due to purchase of unneeded fertilizer. Cucumbers tolerance to salt build-up in the soil ranges from moderate to sensitive.

   Estimated rates of nutrient removal for N-P2O5-K2O-MgO-CaO in fruits, leaves and stems with yields of 10,000 lbs/Acre are 32-9-44-6-23 lbs/Acre, respectively. Over 80% of the total crop nutrient removal takes place during the fruiting stage of crop growth.

              

  

Greenhouse studies of fruit growth and nutrient uptake rates in the continental U.S. indicate that cucumbers respond better to nitrate than ammonium N fertilizer sources. This results in greater Ca, Mg, and K levels in the fruit. Recommended fertilizer rates for Hawaii are 1,500 to 2,000 lbs. per acre of 15-15-15 or similar N-P-K fertilizer. Band half of the fertilizer 3 inches to the side and 3 inches below the seed at planting. Side-dress one quarter of the fertilizer rate at 3-4 weeks after planting and the remaining quarter, 6 - 7 weeks later. With the onset of harvest, side-dress every two weeks with a 3:1 mixture of sulfate of ammonia (21% Nitrogen): muriate of potash (61% potassium) or a 1:1 mixture of urea (46% nitrogen): muriate of potash at a rate of 200 lb per acre. Since N and K tend to leach, apply additional fertilizer after a heavy rain.

  On soils very low in available phosphate, apply 1,500 lb/Acre of treble super phosphate (47% phosphorus) or 1,500 lb/Acre of monoammonium phosphate (11-52-0). If both lime and phosphates are required, both should be incorporated together 8 - 12 weeks before planting.