Actual proof of top-dressed nitrogen method based on nitrate diagnosis with petiole sap of tomato in farmer's greenhouse
2006
Yamamoto, F.(Chiba-ken. Agriculture Research Center (Japan)) | Matsumaru, T.
A technique for reducing fertilizer application while maintaining harvest by top-dressing based on nitrate diagnosis of petiole sap in the semi-forced cultivation of tomatoes was demonstrated at farmers' greenhouses where soil conditions and fertilizer application practices were different. Petiole sap from leaves beneath fruit which was 2-4 cm was measured for nitrate concentration and top-dressing based on nitrate diagnosis was applied when the nitrate concentration fell below 2000 mg L(-1). Top-dressing based on nitrate diagnosis could be maintained at 1000-2000 mg L(-1) during the harvest time when the nitrate concentration of tomato petiole sap decreased to the minimum under these conditions and harvests equivalent to those obtained by top dressing conventionally applied by the farmers were secured. The amounts of top-dressed nitrogen ranged from 0-50% of those conventionally applied by the farmers. In addition, soil nitrate after cultivation with top-dressing based on nitrate diagnoses decreased considerably from that with top dressing conventionally applied by the farmers. Soil nitrogen was thought to be utilized effectively. Both a simple reflection photometer and nitrate test strips were used for the measurement of the nitrate concentration of tomato petiole sap. The nitrate test strips were considered practical because they were easy to handle in the field and low in price.
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