Vegetation Relationships – Vegetation Factors for Soybean Crop

Soybeans belong to the group of plants that require high temperature. It begins to germinate at 7-8 ° C, and requires, for the period of sowing and emergence, active temperatures of 110-130 °.

The temperature requirements of soybean plants during the main vegetation stages are as follows: – For germination, the temperature of soybeans requires 6-7 ° C and an ideal temperature is 20-22 ° C; – soybeans for the emergence of sowing require a temperature of at least 8-10 ° C and an optimal temperature of 20-22 ° C; – for the formation of the reproductive organs, soybeans need 10-17 ° C and the optimum temperature is 21-23 ° C; – for flowers, soybean cultivation needs 17-18 ° C and the optimum temperature is 22-25 ° C; – the formation of soybean seeds requires 13-14 ° C and the optimum temperature is 21-23 ° C; – For baking, soybeans need 8-9 ° C and the optimum temperature is 19-20 ° C.
Throughout the entire vegetation period, early soybean varieties claim 880 °, early varieties 1170 °, semi-late 1260 °, and late 1370 ° (accumulated temperatures above the biological threshold of 10 ° C).
The differences between early and late varieties can reach 500 active degrees. In Dobrogia, early cultivars complete the vegetation period in 109 days (seed moisture at harvest 11%), while late cultivars have a vegetation period of 156 days (seed moisture at harvest 15.5%).
In the emergence stage, soybean plants are more resistant to low temperatures than plants of the legume family (beans). Temperatures from minus 2, minus 2.5 degrees Celsius, for a short time, do no harm. A temperature of minus 3°C causes significant damage to soybean plants in the 3-leaf stage. Soybean plants are generally endangered due to late blight.
Soybean is a plant with relatively high moisture requirements. According to some authors, compared to the years when the precipitation regime is optimal, in drought conditions, soybean production decreases by 33-61%. The transpiration coefficient of soybean is 500-700. During the seed formation stage, the soybean plant loses 300-350 grams of water per day, compared to 150 grams around flowering.
High humidity during seed formation ensures a satisfactory yield, even if the humidity is low during flowering. However, if during the period of seed formation the moisture is insufficient, the production is significantly reduced, even if the moisture is optimal during the flowering period. Thus the stage of soybean seed formation is the critical stage for the hydration factor. While drought during the flowering period reduces production by 14-52%, while drought during the period of grain filling reduces production by 41-87%. Areas with continuous harvesting of soybeans are characterized by humid summers, especially in the second half of the growing season.
The progress in water consumption in soybean crop in the forest-steppe region of the country shows that the maximum water consumption is achieved in June and August, especially in July and August, when 70-90% of the consumption is due to the transpiration process.

In the southern part of the country Due to the drought that occurred in July and August without irrigation, soybean production remains low and very volatile from year to year.. Under these conditions, the genetic production capacity of the cultivated varieties could not be reached. With the exception of some lands in the Danube, soybean cultivation in the south and southeast of the country requires irrigation, and this plant must undoubtedly be among the important plants grown in areas designed for irrigation.
In Plain Banat, the maximum consumption of soybean water is 5.2 mm per day. In this area, a water deficit of 2.0-3.2 mm per day often occurs.
The water deficit, during the critical period in soybean cultivation, was lower in the cultivation areas of Transylvania and the northern half of Moldova.
There is no doubt that insufficient water during the vegetation of soybeans adversely affects all components of production. But the hardest hit is the 1000-grain block. This production component shows the greatest sensitivity to water deficiency. In two different crop years, Beltino in Plain Al Banat found a mass difference of 1,000 grains of 42.5 grams or 25%. Because of this, the lack of water in soybeans during the filling of the grain causes the greatest decrease in production.
Soybeans are a short day plant. A displacement of the soybean plant by 400-500 km to the north or south leads to a deviation of the vegetation period by 20-24 days.
Soybeans provide the highest yield in neutral soils, or with a pH of about 6.5, rich in humus, phosphorous, potassium and calcium, with an average consistency. Soybeans grow well in black and reddish-brown reference soils. In the dams of the Danube, soybeans find almost ideal conditions for plants, both in terms of climate and soil. Particularly high yields of soybeans also ensured in riverine-lactrin (previously flooded) soils.
The riverine and lake soils (previously flooded) throughout the Danube meadow must be attributed to the cultivation of soybeans. In this soil, soybeans are likely to find the best vegetation conditions in all of Romania.
Sandy soils, saline soils or soils with excessive moisture are not suitable for soybeans.

Soybean ecological cultivation areas
When analyzing soybean requirements closely in relation to climate, it can be emphasized that the highly favored region of Romania is limited to the Western Plain, the Transylvanian Plain and the Low Gygia. Within the highly favorable area, primarily river meadows (Mureș, Târnave, Someș, Timi, Siret, etc.), chernozems and soils with soybean plant inputs should be considered.
From the research done, it appears that in the very favorable region, 67-96 mm of rain falls in June, 57-76 mm in July, and 48-96 mm in August. As such, plant water requirements during peak consumption period are largely covered by precipitation that normally falls.
In the above-mentioned areas, among the two factors, humidity and temperature, the latter should be considered as the main limiting factor. Because of this, the success of soybean cultivation in the highly favorable region is determined, first of all, by the varieties grown. With the exception of Plain Banat, early, semi-early and sometimes some late varieties should be planted in a very favorable area.
The closed enclosures of the Danube meadow should also be included in the very favorable area for soybean cultivation, where, together with groundwater supplies and alluvial soils (except for pebbles), the microclimate of the meadow protects plants from atmospheric drought and frequent heat waves in the southern part of the country. As mentioned, in the previously flooded soils of the Danube, soybeans provide the highest yields in Romania.
The preferred area is located in the southern part of the country (the chernozems region of the Roman plain). In this region, the limiting factor for production is water. The average yield of soybeans under normal growing conditions is only 20-25 f/ha.
In the southern part of the country and the southeastern part, caloric regime, the period of active temperatures is very favorable for soybeans. The water supplied through irrigation complements the set of factors very favorable for soybean, so that the south and southeast of the country are currently registered as favorable areas for the cultivation of this plant. Irrigation of soybeans in the southern part of the country (Burgan, Dobrogia, southern Moldova) is considered the most important measure to achieve high production. Each mm of irrigation water increases the yield of soybeans by 4-6 kg. A stream of 25-30 V / ha is achieved on irrigated lands. The southern irrigated region of the country allows soybeans to be grown as cereals (early varieties) and as a second crop, in the remnants of previously harvested grassy cereals.
In the preferred region for soybeans in Moldova, the greatest attention should be paid to the choice of the land on which this plant will be grown. It is required to avoid erosion of loose soil or soil that is frequently exposed to the erosion process.
Taking into account the value of soybean as a forerunner and improver of soil fertility, an attempt is made to expand this culture also outside the zone of chernozioms, on reddish-brown soils and even in podzolas.
In the reddish-brown soil zone, soybeans provide satisfactory yields without special measures compared to soybeans grown on chernozem plants. Sometimes red-brown products are produced at the production level on chernozems, without irrigation.
In order to raise the average production of soybeans per hectare, a greater concentration of the yield is required as most of the requirements of the plant are met. Farming should extend to the south, under irrigation conditions, in the Danube, in the Banat Plain, in Transylvania and in the northeastern region of Moldova. The ‘micro-zones’ with the most favorable conditions for soybeans should be exploited in all cultivation areas.

Victor Vatamano

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