Articles
A FIVE YEAR RESEARCH ON TWO COMBINED DOSES OF WATER AND FERTILIZERS APPLIED TO TOMATO AND LETTUCE GROWN IN GREENHOUSE
Yield, product quality, balance among nutrients applied with fertilizers, plant uptake and those released in the soil were also evaluated.
The research was carried out in glasshouses for five years; tomato and lettuce were in successive culture within the year.
The total amount of fertilizers distributed each year was 225–175–175 kg ha-1 of N, P2O5, K2O (125–100–100 kg ha-1 for tomato) and 450–350–350 kg ha-1 (250–200–200 kg ha-1 for tomato) as double dose.
The water, applied as sprinkle-system on the EV basis (100% of EV of the lower water volume applied measured by "Class A" evaporimeter), was 225 and 450 m3 ha-1 for tomato and 125–250 m3 ha-1 for butter-lettuce.
The highest yield was obtained, on the average, both by highest fertilizer rate and water volume; especially the highest irrigation volume increased the tomato fruits and lettuce weight, but reduced their dry matter content.
The nutrient uptake (N-P2O5-K2O) made by the two crops was, on the average, about 165–40–219 kg ha-1 and 66–24–100 respectively for tomato (plants and fruits) and lettuce for a total of 231–64–319 kg ha-1. No significant differences were observed in nutrient absorption from the comparison between two different water regimes.
Referred to highest fertilizer rate, the nutrient uptake represent about the 56% for nitrogen, 18 % for phosphorus and 91% for potassium.
From these results, it is evident that phosphorus fertilizer rate was too high, for both tomato and lettuce, while those of nitrogen and potassium need a better balancing on the basis of plant uptake.
Nevertheless the soil analyses showed a constant nitrogen and potassium content and an increasing in phosphorus and total salinity.