Characteristics of sowing and cultivar qualities of vegetable crop seed

When planning a sowing campaign, it is important to consider the germination characteristics of a specific crop. The starting supply of nutrients for seedling development is localized depending on the plant species:

• in the endosperm;
• in the perisperm (in beet, spinach, and chard);
• in the cotyledons (in cucurbits, legumes, asteraceae, and brassicas).

Keep in mind that for asteraceae, amaranthaceae, and apiaceae crops, it is not pure seed that is sown, but dry fruits. An additional outer fruit coat, formed from the ovary or flower walls, slows down moisture access to the embryo. For such crops, especially thorough soil preparation is required before sowing.

For most other vegetable crops, the cotyledons are brought to the soil surface during germination. They quickly turn green, increase in size, and begin to actively photosynthesize. Thanks to this, young plants easily tolerate the stress of transplanting and are perfectly suited for the transplant method of cultivation.

Seed size directly determines the energy supply for the start of the sprout. Large seed material contains more nutrients, ensuring uniform emergence even in unfavorable field conditions. Below is a classification of crops by seed size — this will help to properly calibrate seeding units.

How to control varietal and sowing qualities of seeds

Crop yield directly depends on seed reproduction — the number of re-sowings after super-elite and elite generations. Each subsequent generation inevitably loses yield potential, even if the plants externally fully correspond to the standard. Upon receipt of a batch, be sure to check the documents and perform a visual inspection to timely confirm the authenticity of seeds of hard-to-distinguish crops.

Varietal purity of seeds is determined by specialists in the field using crop testing methods. This indicator reflects the percentage of plants that have fully retained the cultivar traits. Depending on this, all seed material is divided into three categories, for each of which strict standards are established.

• Number of seed varietal purity categories — 3
• Varietal purity of category I tomato — at least 99.0%
• Varietal purity of category I pea — at least 99.5%
• Minimum purity of category III radish — 85.0%

Indicators from a laboratory quality certificate cannot be directly transferred to the field. Practice shows that actual field emergence is always 20–30% lower than laboratory emergence. The difference depends on weather whims, sowing dates, and the quality of soil preparation. To obtain the planned plant density, the agronomist must adjust the application rate for the actual batch of seeds.

All standard application rates in reference books are calculated for ideal first-class seeds with maximum purity and emergence. If your batch indicators differ, the actual rate is increased. To do this, the sowing suitability of the seeds is calculated in advance.

1. Find the values of laboratory emergence (A, %) and seed purity (B, %) in the quality certificate.
2. Calculate the sowing suitability (S, %) using the formula: S = (A × B) / 100 %.
3. Use the obtained percentage of suitability for a proportional increase in the application rate in the field.

In certificates, seed inspections record a complex of essential parameters. Specialists determine emergence, germination energy, viability, purity, mass of 1000 seeds, humidity, weediness, and infection. Germination energy is evaluated in half the time — it shows the uniformity of emergence. Purity reflects the share of the main crop, and the remainder consists of live or dead impurities. If a batch does not meet the requirements of the first or second class, it is rejected or sent for further processing.

• Decrease in field emergence — by 20–30%
• Seed storage temperature — 0…+5 °С
• Warehouse air humidity — no more than 60%
• Standard seed moisture — 9–11%

Regulatory requirements for seed varietal purity

When planning purchases or preparing your own seed stock, always refer to state standards for varietal purity. Strict limits on seed material categories have been established for each crop. Below are the regulatory requirements that will help assess the quality of a purchased batch:

Post-harvest preparation and seed storage conditions

The viability of seed material is determined in the field, but maintaining it until sowing is a separate task for the agronomist. Mistakes during the drying, cleaning, or sorting stages can quickly ruin even a high-quality batch. To avoid this, the entire cycle of post-harvest preparation is carried out in strict sequence.

1. Thorough cleaning and sorting of the harvested bulk with the removal of foreign impurities and defective seeds.
2. Drying of seed material to moisture levels no higher than standard (for most vegetable crops — 9–11%, for beets — 13–14%, for peas — 14%).
3. Holding the seeds during the natural physiological dormancy period, which lasts from several days to 2–3 months.
4. Submission of the prepared batch for analysis to the seed inspection agency to determine germination energy and total germination.
5. Placing standard seeds into storage under controlled conditions.

The duration for preserving seed quality depends directly on warehouse conditions. In specialized facilities with climate control, it is possible to maintain the viability of vegetable seeds for decades. To achieve this, air environment parameters in the warehouse are monitored around the clock.

• Air temperature — 0…+5 °С
• Relative humidity — no more than 60%
• Viability maintenance period — from 5 to 20 years

If seeds are stored under ordinary barn conditions without climate control, viability is lost much faster. In this case, maximum storage times are strictly limited by the biological characteristics of the crops.

Conditions for uniform seed germination in the field

For a fast and synchronized start of field seedlings, an agronomist needs to balance three factors: moisture, heat, and air access. Without sufficient water, plant enzymes are not activated, and the nutrients in the seed will not be converted into a form accessible to the embryo. Sowing technology must ensure tight contact of the seed with moist soil at an optimum temperature.

The requirement for moisture during swelling depends on the chemical composition of the seed of a specific crop. Seeds rich in proteins require the most water, while starchy and oil-bearing seeds require the least.

The swelling dynamics also differ among crops. While seeds of legumes, Brassicaceae, cucurbits, Solanaceae, and Asteraceae swell completely in a few days, others require more time due to protective barriers:

• Apiaceae (carrot, parsley, celery): the process takes one and a half to two weeks, as essential oils in the seed coat hinder moisture penetration.
• Crops with a hard seed coat (onion, asparagus, sea kale, artichoke): absorb water slowly due to the high density of the seed coat.

Soil temperature directly regulates the rate of seedling emergence. In cold soil, all physiological processes slow down. To control sowing dates, use the germination temperature thresholds of the crops as a guide.

• Minimum for cold-resistant crops — +1...+4 °С
• Optimum for cold-resistant crops — +22...+25 °С
• Minimum for heat-loving crops — +12...+16 °С
• Optimum for heat-loving crops — +26...+30 °С

From the moment of germination, seeds begin to respire intensively, which is why they require a constant supply of oxygen. The air-gas regime in the seed zone is often disrupted due to waterlogging and water stagnation in the soil, the formation of a dense crust, or excessive compaction of the top layer by machinery wheels. High-quality pre-sowing tillage and timely breaking of the soil crust help maintain the balance of heat, moisture, and air for uniform emergence.