Effect of KNO3 on CO2 exchange rate, nutrient concentration and yield of Meloidogyne incognita infected beans

One-week-old Phaseolus vulgaris plants were inoculated with 4 O00 second stage Meloidogyne incognita juveniles and fertilized with Hoagland solution containing none, normal, double, or quadruple strength KN03 and compared with uninfected controls that received normal strength Hoagland solution. The leaf area and the photosynthetic and dark respiration rates were measured at intervals from O (before) to 28 days after inoculation. At 28 days, plant dry weight, number, of pods and seeds and the concentration of Ky Ca, Mn, Fe, Cu and Zn in the leaves, stems and roots and NO3 in the leaves were determined. The soil pH, conductance and the soil concentrations of PO4, Na, B, Mg, and S04 were also measured. The photosynthetic rate and respiration rate increased with the addition of KN03 in the nematode-infected plants but not higher than in the uninfected controls. The concentration of K in the shoot and NO3 in the leaves increased while the other elements generally decreased with increasing supplementary KN03. In the soil, NO3, Ky Ca, Mn, S04 and conductance decreased while the pH increased with decreasing supplementary KNO? Fewer pods and seeds were formed in the nematode-infected plants which did not receive supplementary KNOP The results show that under the prescribed conditions, for a nematode-infected bean plant to yield closest to the uninfected and fertilized with normal strength Hoagland solution it required a four fold supplement of KN03.