The influence of the geographical origin of crops on agricultural practices and plant development

Weed control and soil requirements: why the crop’s origin is important

When planning a protection scheme and selecting a field for a crop, an agronomist needs to consider its geographical origin. During the formation of crop genotypes in 31 and subtropical zones, the intensity of insolation and temperature conditions is higher than in the north, and heat never limits their development. This is precisely why short-day crops always require abundant "southern" sun. During the first growing season, they direct maximum assimilates toward forming a robust root system in order to reach deep, moist soil layers more quickly, which is why their above-ground parts grow slowly during the initial stages.

In temperate climates, this physiological characteristic creates serious problems during cultivation. Long-day weeds grow vigorously upward from the early phases of development and easily shade out crop seedlings. Without timely treatments, it is extremely difficult to obtain a good harvest of short-day crops. At the same time, local long-day species, due to the rapid starting growth of their above-ground mass, compete much more successfully with weed vegetation.

Origin also dictates the plant’s requirements for soil conditions:

• Short-day crops require neutral or slightly acidic soils with a high soil adsorption capacity. In the zones of their origin, soils are usually medium or heavy in texture, rich in 1- and 2-valent cations, and have a neutral or alkaline reaction.
• Long-day crops tolerate acidic, light-textured soils with a low content of nutrients better. However, they fully realize their potential productivity only on slightly acidic and neutral lands rich in nutrients.

Sum of active temperatures and moving crops to the north

When moving short-day crops to the north, the growing season lengthens, and plants begin to actively accumulate green mass. In northern latitudes, the duration of the growing season is strictly limited by the frost-free period. For short-day species, the critical factor becomes the timing of the return of spring cold spells and the onset of autumn frosts. Furthermore, the northern position limits the sum of active temperatures (daily average temperatures above the biological threshold of 10 °C) required for complete ontogenesis.

To pass through each stage of ontogenesis, a plant requires a strictly defined sum of active temperatures inherent in its genotype. Knowing this indicator for a specific cultivar, an agronomist can accurately determine the range for reliable seed maturation. Calculating accumulated heat across individual interphase periods allows for high-precision forecasting of the onset of each developmental phase directly in the field.

To overcome these limitations, breeders create new ecotypes. For example, northern ecotype soybean cultivars obtained through radiation mutagenesis require only 1700–1800 °C, which guarantees seed maturation near Moscow and Minsk. Similar results have been achieved with corn: modern hybrids of this tropical crop mature for grain up to 55° N, yielding a harvest of waxy and full ripeness.

• Active temperature threshold for physiological processes — 10 °C
• Heat requirement for northern soybean cultivars — 1700–1800 °C
• Maturity limit for corn grain hybrids — 55° N
• Average sum of active temperatures in the Minsk region — 2200 °C
• Average sum of active temperatures in the Moscow region — 2000 °C