[Nitrogen requirement and fertilization efficiency of cantaloupe (Cucumis melo L. var reticulatus Naud)]
1991
Suarez F, Domingo (Universidad Catolica de Chile, Santiago (Chile). Fac. de Agronomia)
A field trial was carried out to determine the parameters needed to calculate nitrogen requirements of cantaloupe (Cucumis melo L. var reticulatus Naud). The field trial consisted of different nitrogen rates, from zero up to 160 kg N/ha, in order to select plants with adequate N nutrition (neither excess, nor lack) for the estimation of the parameters needed to determine nitrogen requirements. Beside, the nitrogen fertilization efficiency was calculated. The parameters were the Harvest Index (HI), the Internal Nitrogen Requirement (INR) and the dry Matter Content (%) in the fruit. HI= fruit dry matter/total dry matter; INR(%)=100 total N absorbed/total dry matter; Efficiency(%)=100*N absorbed from fertilizer/N applied as fertilizer. It was found that HI was 0.81, INR was 1,85% the dry matter content in the fruit was 12.6% and the fertilization efficiency was 54.8%. A conversion factor to obtain nitrogen requirement-knowing the expected yield-was developed considering all the parameters together. This factor was 2 875 g N/ton of fresh fruit. Assuming different soil nitrogen supplies and different expected yields it is possible to apply the equation for nitrogen fertilizer rate when crop nitrogen requirement is larger than soil nitrogen supply: N Fertilizer Rate=Plant Requirement-Soil Supply/Fertilization Efficiency. This approach allows to calculate the optimum physical nitrogen rate as well as the economical optimum rate
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