Influence of nitrogen on sown and ratooned upland kangkong (Ipomoea aquatica Forsk.) at two planting densities.

Abstract

Kangkong cv. Large Leaf was grown in a glasshouse at 2 densities (20 or 44 plants/msuperscript 2) and at 4 rates of N as calcium ammonium nitrate. The crop was either ratooned (5 crops) or cut and resown (3 crops) starting 6 weeks after sowing. Increasing the rate of N application from 100 kg/ha to 250, 500 and 750 kg/ha increased the total at 18 weeks by 3.8, 5.1 and 6.1 kg/msuperscript 2, respectively, and increased the crop nitrate content from 599 mg/kg fresh weight at 100 kg/ha to 3812 mg/kg at 750 kg/ha; stems had a higher nitrate content than leaves. The high plant density gave a 3 kg/msuperscript 2 greater yield than the low density, and ratooning gave a 5 kg/msuperscript 2 greater yield than the resowing method. (Abstract retrieved from CAB Abstracts by CABI’s permission)