Influence of Potassium and Nitrogen Fertilization on Parasitism by the Root-knot Nematode Meloidogyne javanica

The influence of various c oncentrations of K, nitrogen sources, and inoculation with root-knot nematode Meloidogyne javanica were evaluated in tomato plants. Increased potassium concentration increased top and root fresh weights of intact plants and fresh weights of excised roots. Nitrate-fertilized plants weighed more than plants receiving ammonium independent of the K level in the medium. Nematode counts on roots were not affected by nutritional differences in intact or excised roots. In intact roots a high percentage of males was recorded at low K levels, whereas in excised roots the proportion of males in the population rose as the K levels increased. Inoculated intact roots accumulated K when the level of potassium supply was low; infected excised roots contained less K than did nematode-free roots.