THE INFLUENCE OF PEAT LAYER THICKNESS AND MINERAL FERTILIZERS ON GREENHOUSE TOMATO YIELDS

Sphagnum peat moss is now often used for producing greenhouse plants. Baker 1957, Penningsfeld 1961, Penningsfeld and Kurzman 1966, Pudelski 1967, obtained the highest yield of greenhouse tomatoes on Sphagnum peat moss when the N:P₂O₅:K₂O ratio was 1:2:2.

The influence was studied of increasing doses of mixed MIS-2 fertilizer, containing all the macro- and micro-nutrients, on the yield of greenhouse tomatoes grown on 15 and 25 cm deep layers of sphagnum peat moss.

Tomatoes were grown on benches in sphagnum peat moss which pH after liming ranged from 5.4 to 6.0. The experimental conditions are presented in table 1.

Before planting tomatoes in the third rotation the peat was disinfected with Captan in 1967 and with Ceresan in 1968.

The MIS-2 mixed fertilizer was used. It consists of two parts of the following composition:

Part A (macronutrients)

N - 5.1% as ammonium nitrate

P₂O₅ - 10.2% as superphosphate

K₂O - 10.2% as potassium sulphate

MgO - 1.5% as magnesium sulphate

N:P₂O₅:K₂O:MgO = 1:2:2:0.3

Part B (micronutrients)

Fe - 7.3% as FeSO₄·7H₂O

Mn - 2.7% as MnSO₄

Cu - 9.1% as CuSO₄·5H₂O

Zn - 0.6% as ZnSO₄·7H₂O

B - 1.6% as H₃BO₃

Mo - 2.7% as /NH₄/₆Mo₇O₂₄·4H₂O

Part B (micronutrients) was added at the beginning of experiments I and II to all treatments in the same amount 135 mg per litre of peat. Micronutrients were dissolved in water and acidified to pH 3 with sulphuric acid.

In both experiments tomatoes were grown in three rotations: 1st in spring, 2nd in fall, 3rd in the following spring.

In experiment I in spring 1966, different doses of part A MIS-2 mixed fertilizer were applied (table 2). In treatments where top dressings were applied macronutrients were added in doses 1 g/litre peat at two week intervals beginning on 10 March.

In fall 1966 (second rotation) before planting all treatments received