Experience in the Use of Peat Substrate and Peat-Based Fertilizers in Greenhouse Vegetable Cultivation

V. S. Boiko, A. I. Ponomareva, N. G. Vasilieva

Greenhouse crops—especially cucumbers—require, for the growth and development of the root system, a large reserve of moisture and air in the root-inhabited substrate.

For growing cucumbers in greenhouses, sod-humus soil is used; it must be loose and highly fertile.

But preparing such soil is almost impossible under the conditions of large greenhouse-hotbed combines, as well as under the conditions of future greenhouse-hotbed farms in the north of the West Siberian Lowland, where the soils are podzolized and waterlogged, and manure is often unavailable.

Recently, a transition has begun to various soil mixtures in which the proportion of lowland peat sometimes reaches 60–70%. But even such a substrate, after repeated waterings, silts up and requires frequent loosening; moreover, the procurement of soil and manure, as well as loading greenhouses with them, is very labor-intensive work.

At present, the method of growing vegetables on solid substrates—gravel, crushed stone, expanded clay—is becoming widespread. But this method, despite its many advantages, has drawbacks. Chief among them are the expensive equipment needed to mechanize the supply of solutions, the maintenance of a special agrochemical laboratory, etc.

One of the simple and reliable soil substitutes for greenhouses and hotbeds can be peat, both high-moor and lowland, with a degree of decomposition of no more than 15%. Such peat is three times lighter than sod-humus soil, and consequently loading it into a greenhouse is considerably cheaper.

Peat has high antiseptic properties and is free of weed seeds, which is important for hotbed farming. Owing to the good physicochemical properties of peat, favorable conditions are created in it for the development of the plant root system [1]. Also of no small importance is the fact that, after peat has been used in a greenhouse, it is a good fertilizer for open ground. The use of peat in a greenhouse for more than two years is economically disadvantageous, since it is more profitable to use it for other purposes, while on the racks fresh peat with a better water-air regime should be provided. It is also significant that peat reserves in the Soviet Union are practically unlimited, especially here in Siberia. Therefore peat culture in our country is promising and in recent years has been becoming widely used.

The study of the possibility of replacing soil on the benches of technically heated greenhouses with peat substrates, and of the nutrition regime of cucumbers grown on peat, has been carried out by the Department of Agrochemistry of the Novosibirsk Agricultural Institute since 1964 at the “Kirovets” state farm of the Novosibirsk District Production Administration of Agriculture.

Reconnaissance experiments in 1964 showed that:

a) the use of peat as a substrate provides higher yields than soil;

b) the best fertilizers on peat substrates may be peat-mineral granules and mineral fertilizers.

As the substrate in 1965, lowland peat from the “Syrovatka” deposit was used, with a degree of decomposition of 5% and a salt pH of 6.8, either in pure form or with the addition of 25% expanded clay by weight. The control was a soil mixture of the following composition: 25% soil, 25% strongly decomposed peat, and 50% weakly decomposed peat.

Peat-mineral granules and tablets, nutrient solutions, and mineral fertilizers were used as fertilizers. Mineral fertilizers were introduced into the substrate in dry form. On the soil mixture, mineral fertilizers and manure were applied as top dressings, as recommended by the cultivation technique proposed by NIIOKh, with certain modifications on the farm.

The plants’ nutrient requirements were calculated, for a specified yield, according to the method proposed by Prof. Zhurbitsky [2]. For a fruit yield of 50 kg per 1 sq. m of bench, the following quantities of nutrient elements were given (Table 1).

Table 1

Application of nutrient elements and their ratio by experimental variants in 1965
(g per 1 sq. m of bench)

As can be seen from Table 1, three levels of nutrition were created, with different ratios of $N : P_2O_5 : K_2O$. The calculation of fertilizer doses for the variants with mineral fertilizers and granules was carried out according to the removal of nutrients with the fruit yield; for the variants with nutrient solutions and tablets, the calculation was made according to the Abele solutions; for the variant with mineral fertilizers and manure, according to their actual application in accordance with the agronomic plan adopted on the farm.

These fertilizers were applied on three substrates: 1) peat, 2) peat with the addition of expanded clay, and 3) soil mixture.

Mineral fertilizers, both dry and as nutrient solutions, were not applied to the soil, and manure top dressings were carried out only on the soil (farm control). On the peat and peat–expanded-clay substrates, cucumbers were grown without the use of manure.

The experiment was laid out in four replications. The area of the plots ranged from 2 to 4.3 sq. m of usable area, i.e., one rack per treatment. Cucumbers of the variety “Adler multi-fruited” were planted in their permanent place as germinated seeds on January 8 and 9. The plants grew and bore fruit until November without replacement. The final harvest was carried out on November 2. Yield was recorded from each plot for all treatments of the experiment. The results of yield accounting as of September 1, 1965, are summarized in Table 2.

Table 2

Effect of fertilizers on cucumber yield on different substrates
(kg per sq. m of rack as of September 1, 1965)

Note. Experimental error \(P \% = 4.01\).

From Table 2 it is evident that the highest cucumber yield as of September 1 was obtained on the peat substrate fertilized with Abele nutrient solutions—47.12 kg per sq. m of rack.

The smallest amount of fertilizer was expended on growing 1 kg of fruit on peat substrates when mineral fertilizers were applied in dry form (23.5 g). Under the usual farm method of growing cucumbers on a soil mixture with top-dressing by manure and mineral fertilizers, the yield was 45.11 kg, while fertilizer expenditure per 1 kg of yield amounted to 92.5 g. The highest average yield by substrate with the use of different fertilizers was obtained on slightly decomposed peat—44.5 kg/sq. m. On different substrates, the highest average yield was obtained with irrigation by Abele solutions—46.13 kg per sq. m.

A comparison of labor operations by the treatments of the experiment (Table 3), carried out during cucumber cultivation after the racks had been filled with substrate, shows that the most labor-intensive treatments were those with the application of fertilizers in the form of nutrient solutions. Irrigation–top-dressing was carried out twice a week at 10 liters per 1 sq. m. The treatment using top-dressing in the form of solutions of mineral fertilizers and manure was also labor-intensive. A particularly labor-intensive operation is the delivery of manure and its distribution in the racks. Twelve manure top-dressings were made; in all, 60 kg of manure per sq. m of rack was applied.

Table 3 gives the types of work by which the treatments differed; all other plant-care operations were carried out identically in all treatments of the experiment.

In addition, the possibility of growing cucumber seedlings on loose, slightly decomposed peat was studied. For this purpose, a special experiment was laid out in which the quality of the seedlings grown was checked by the size of the yield obtained.

For this purpose, seedlings were grown: a) in loose peat, in which the upper five-centimeter layer was mixed with mineral fertilizers; b) in peat sods cut from an undisturbed layer.

peat and soaked in nutrient solution; c) the control was seedlings grown in peat–humus pots, as is generally accepted on all farms. The seeds for growing seedlings were sown on January 13, and the seedlings were transplanted to the permanent site on January 27.

Table 3

Number and types of additional labor operations for caring for cucumbers in the greenhouse

Labor inputs were lowest in the variant “Seedlings grown on loose peat.” As can be seen from Table 4, cucumber seedlings intended for use in greenhouses can be grown on peat sods and loose peat instead of labor-intensive peat–humus pots.

Table 4

Yield of cucumbers obtained from seedlings grown on different substrates, as of August 1, 1965

During the growing season of the plants, experiments were carried out to study the effect of spraying with solutions of sodium humates on cucumber yield. The sodium humates were isolated from peat. The plants were sprayed from April 3 to May 30 regularly once a week at two concentrations—0.01 and 0.005% (Fig. 1).

The control was the variant in which spraying was carried out with water. As can be seen from the graph, yield during the first treatments increased sharply (116 and 118% relative to the control), and then, as spraying was repeated, gradually declined, and by the end of the experiment it exceeded the control by only 2–4%.

From this it may be concluded that, by applying such a growth stimulant as sodium humates at the beginning of fruiting, a larger yield of early fruit can be obtained.

Watering onions during forcing for greens with a 0.005% concentration of sodium humates gave an increase in green mass 12.4% greater than the control watered with water.

On the basis of the results of experiments conducted at the Kirovets state farm in 1964–65, the following conclusions may be drawn:

Fig. 1. Effect of spraying plants with a solution of sodium humate of different concentrations on the increase in cucumber fruit yield.

1. The use of peat with a low degree of decomposition gives good results both in growing seedlings and when using it as a soil substitute on greenhouse benches under soilless crop culture.

2. The good physicochemical properties of peat make it possible to obtain high cucumber yields with a small number of top dressings. Both granules and tablets make it possible to apply large doses of mineral fertilizers without causing burns to the root system.

3. The application of mineral fertilizers in dry form on a peat substrate gives the greatest economic effect. When fertilizing with nutrient solutions, numerous top dressings are necessary.

4. The use of peat in growing seedlings improves their quality, increases fruit yield, and sharply reduces labor costs by eliminating all operations associated with making pots.

5. Spraying plants with sodium humates from peat accelerates the yield of early cucumbers, and, when watering onions grown for greens, increases the yield of marketable greens.

REFERENCES

1. E. Abele. It is advantageous to replace greenhouse soil with peat. Sad i ogorod, No. 12, 1959.

2. Z. I. Zhurbitskii. Physiological and agronomic foundations of the application of fertilizers. Publishing House of the Academy of Sciences of the USSR, Moscow, 1963.