Nitrogen fertigation of greenhouse‐grown French beans

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Abstract
Water containing 3.6, 7.2, or 10.8 mmol N/L and uniformly supplied with 2.0 and 5.0 mmol/L of P and K, respectively, was used for irrigating greenhouse‐grown French beans (Phaseolus vulqaris cv. ‘Blue Lake'). The fertilizers were applied with every irrigation via the irrigation stream. The plants were grown in pots, each filled with 12 kg of soil. In all treatments a 0.3 leaching fraction was allowed. The total amounts of N applied in a total amount of 180 L water per pot were 9, 18, and 27 g/pot for the three N levels, respectively. The N level induced considerable differences in soil salinity among treatments. In the root volume of the treatment fed with the lowest N level the residual NO ‐N concentration in the soil solution was negligible, whereas with the highest N level it ranged throughout the growing period between 15 and 20 mmol/L. With the N‐treatment 7.2 mmol/L which gave as high yield (1.8 kg/pot) as the highest N level, NO3‐N was mostly around 3 mmol/L. It was concluded that 7.2 mmol N/L applied with every irrigation via the irrigation stream is adequate for high yield without unduly increasing soil salinity or wasting N.