Petiole sap testing sampling procedures for monitoring pumpkin nutritional status
2003
Studstill, D.W. | Simonne, E.H. | Hutchinson, C.M. | Hochmuth, R.C. | Dukes, M.D. | Davis, W.E.
With increasing fertilizer costs and the development of nutrient Best Management Practices (BMPs), pumpkin (Cucurbita spp.) growers need a way to monitor nutrient concentration during crop production. Ion specific electrodes are available to determine in the field, nitrate nitrogen (NO3-N) and potassium (K) concentrations in the plant, but currently, no recommendations exist for sampling procedures for pumpkin. Pumpkins were grown at two locations to determine if the number of petioles sampled, the part of the petiole tested, or if the presence of developing fruit on a runner, affected NO3-N and K concentrations in the sap. Nitrate and K concentrations were determined using Cardy meters on the proximal, middle, and distal sections of petioles and on increasing number (from 1 to 60) of middle petiole sections. Nitrate (p = 0.17) and K (p = 0.84) concentrations were not significantly influenced by petiole section. The presence of a developing fruit on the sampled runner did not significantly influenced NO3-N (963 and 913 mg/L without and with fruit, respectively; p = 0.51) and K (3188 and 3000 mg/L, respectively; p = 0.14) concentrations. The coefficients of variation for NO3-N and K remained below 10% for sample sizes greater than 10 petioles. Therefore, growers who want to determine NO3-N and K in pumpkin petioles should use the middle section of at least 20 petioles from the most recently, fully mature leaves from representative plants.
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