engleski

The incidence of BER-affected tomato fruits under influence of the form of N fertilizer

Calcium is a very important nutrient in highly productive fruit growing such as greenhouse- grown tomato (Lycopersicon esculentum Mill.) and Ca deficiency manifests as local decay of fruits called blossom-end rot (BER). It was postulated that Ca uptake can be affected if NH4-N form prevails in the fertilization. The aim of this study was to compare the effect of different N forms (NO3 - , NH4 +) and rates on fruit yield and quality of tomato plants in greenhouse conditions. Tomato plants were grown on substrate made of mixture of soil, turf, chicken manure and sand. Both forms of N were applied separately at three different levels: 300, 500 and 800 mg N plant-1week-1. During the trial, mean number of fruits per truss, number of BER affected fruits, fresh weights of ripe tomato and mean total yield per plant were recorded. Also, leaves and stems from flower initiation to the fruit formation in 8th truss were sampled out of which Ca concentration was determined. Results showed that Ca concentration in leaves and stems was under influence of high air temperature and N form which strongly correlated with BER appearance. In the final harvest no BER tomatoes occurred at the application rate of 300 mg N plant- 1week-1 and very few were observed at 500 mg N plant-1week-1. However, at 800 mg N plant-1 week-1 and high air temperature in the greenhouse, the NH4-N treatments gave the lowest yields, due to high incident of BER tomato fruit. Therefore, fertilization rate of 500 mg N plant-1week-1, regardless of N- form, gave the highest yields in both years where higher yield was observed in the year 2005 with medium N rate supplied as NO3, but very close to that recorded on the same fertilization level with NH4 + form dominated. At the end, excessive N fertilization such as 800 mg N plant-1week-1 with mostly NH4 +-N form implemented in this research, should be applied with precaution in the conditions of high air temperature in the greenhouse, because of feasible disorder in Ca supply of fruits and BER symptoms development.

air temperature ; ammonium nitrogen ; blossom-end rot ; calcium ; fertilization treatment ; greenhouse ; nitrate nitrogen ; tomato

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