STUDY OF VARIOUS NH4+ NO3-MIXTURES FOR ENHANCING GROWTH OF POTATOES/

Two experiments were conducted to determine the effects of various NH4 +-N/NO3--N percentages on growth and mineral concentrations in potato (Solanum tuberosum L.) plants using a non-recirculating nutrient film system in a controlled environment. The first experiment included six NH4+-N/NO3--N percentages at 0/100, 20/80, 40/60, 60/40, 80/20, and 10 0/0 with the same total N concentration of 4 mM. The second experiment included six NH4+-N/NO3--N percentages at 0/100, 4/96, 8/92, 12/88, 1 6/84, and 20/80 again with the same total N of 4 mM. In each experimen t, plants were harvested 35 days after transplanting when tubers had b een initiated and started to enlarge. Dry weights of shoots, tubers, a nd whole plant at the harvest were increased significantly with all mi xed nitrogen treatments as compared with single NH4+ or NO3- form. The enhanced growth with mixed nitrogen was greatest at 8% to 20% NH4+-N. Also, the concentrations and accumulation of total N in the shoots an d roots were greater with mixed nitrogen than with separate NH4+ or NO 3- nutrition. With NH4+ present in the solutions, the concentrations o f P and Cl in the shoots were increased compared to NO3- alone, wherea s the tissue concentrations of Ca and Mg were decreased. It was conclu ded that nitrogen fertilization provided with combined NH4+ and NO3- f orms, even at small proportions of NH4+, can enhance nitrogen uptake a nd productivity in potato plants.