Detailed Explanation of Key Techniques for High-Yield Sesame Cultivation

I. Land Preparation

Sesame seeds are small, the root system is weak, and seedlings grow slowly. Fine land preparation is one of the important measures for achieving full stands and strong seedlings from a single sowing. Sesame is susceptible to waterlogging. In low-lying and rainy areas, ditches should be opened and raised beds made on the basis of plowing and land preparation, so as to drain water and prevent waterlogging. In the urban area of Tianjin, there is little rain or snow in spring. For spring-sown sesame, winter plowing and harrowing should be carried out to preserve soil moisture, and early spring harrowing should be done while the soil is still frozen. For summer-sown fields, after the previous crop is harvested, shallow plowing should be done in time to remove stubble, followed by fine land preparation, so that the soil is fine, loose, and level on the surface, with good soil moisture at the surface, which is conducive to full stands after sowing.

II. Fertilization

Sesame is a crop with relatively high fertilizer requirements. For every 100 kg of seed produced, it requires 9 kg of nitrogen, 2 kg of phosphate, and 9 kg of potassium oxide. Applying sufficient base fertilizer, applying good seed fertilizer, topdressing in stages, and timely increasing potassium fertilizer are effective measures for increasing sesame yield. Base fertilizer should be mainly organic fertilizer. Sesame roots are distributed shallowly, and shallow application of base fertilizer gives a good yield-increasing effect. According to experiments, applying 1500 kg per mu at a shallow depth of 15-18 cm increased yield by 11.7% compared with deep application at 24 cm. Seed fertilizer is used in small amounts but has a high effect and can meet the nutrient needs of the seedling stage. Seed fertilizer can be mixed with seeds for sowing, or broadcast in sowing furrows or holes before sowing. The sowing rate should not be too large. Generally, 5—8 kg of cake fertilizer per mu, or 3—4 kg of ammonium sulfate, or 300—400 kg of farmyard manure is applied. Sesame should be topdressed in stages during the seedling stage, bud stage, and full flowering stage, with obvious yield-increasing effects. Topdressing before flowering can fully meet the nutrient needs during the period of vigorous vegetative and reproductive growth. Spraying phosphorus and potassium fertilizers during flowering can increase capsule number, increase seed weight, and raise oil content. Generally, a 0.4% potassium dihydrogen phosphate solution is used and sprayed on clear afternoons. Spray once every 5—6 days, for 2—3 consecutive sprays, with 50—60 kg of fertilizer solution each time. If rain occurs after spraying, it should be sprayed again.

III. Sowing

Sowing is an important part of sesame production. "Sesame is delicate; if ruined once, there will be no harvest three times." Only by sowing enough and sowing well, and achieving a full stand from one sowing, can stable and high yields be achieved. "Sesame at the Beginning of Summer, millet at Lesser Fullness." Spring-sown sesame is best sown in early May. Sesame sowing methods include drilling, broadcasting, and dibbling, with drilling being preferable. Drilling gives uniform seed distribution, consistent depth, neat emergence, and facilitates thinning for dense planting and field management, but excessive sowing rates must be prevented to avoid overcrowded seedlings. A sowing rate of about 0.5 kg per mu is appropriate. Sesame should be sown shallowly, with a sowing depth of about 3 cm being appropriate. When soil moisture is insufficient, it may be sown somewhat deeper or sown deep with shallow covering soil. After sowing, it should be pressed in time so that the seeds are in close contact with the soil, which helps the seeds absorb water, germinate, and emerge.

IV. Reasonable Close Planting

Reasonable close planting of sesame, increasing the number of plants per unit area, expanding leaf area, fully utilizing light energy and soil fertility, and coordinating the contradiction between individual and population growth so that more organic matter is produced, is an effective measure for increasing yield and oil content. Determining density should be based on a comprehensive consideration of variety characteristics, cultivation conditions, planting methods, and so on. Generally, single-stem varieties with tall plants, tolerance to fertilizer and water, and later maturity should be denser than branching varieties; varieties tolerant to barren soil and widely adaptable, with short plants and early maturity, should be appropriately denser; spring-sown sesame should be thinner than summer-sown sesame. The reasonable planting density for sesame is 6000—7000 plants per mu for branching varieties and 8000-10000 plants for single-stem varieties.

V. Field Management

Sesame seeds are small, and the number of emerged seedlings is more than ten times the number retained. Because seedlings grow slowly, they are easily damaged by seedling overcrowding and weeds during the seedling stage. Therefore, strengthening seedling-stage management and ensuring a full stand of strong seedlings is the key to increasing yield. If rain occurs after sowing and the soil crusts, the soil crust must be broken in time to facilitate emergence. After emergence, shallow hoeing should be done in time to remove weeds and thin seedlings, preventing seedling overcrowding. When seedlings grow 2 true leaves, thinning is carried out; when 4 true leaves appear, final thinning can be done. When pests and diseases are severe, final thinning may be appropriately delayed. During final thinning, retain seedlings according to plan, remove weak seedlings, keep strong seedlings, and retain seedlings evenly. Before sesame flowers, generally 3 to 4 cultivations should be carried out. When seedlings grow the 1st pair of true leaves, the first cultivation is carried out. Cultivation should be shallow rather than deep, mainly for weed control and moisture preservation, and excessive depth should be avoided to prevent root damage. The second cultivation is carried out when sesame grows 2—3 pairs of true leaves, with a depth of 5—6 cm being appropriate. The third cultivation should be carried out at 5 pairs of true leaves, and the depth can be increased to 8-10 cm. When sesame begins to flower, the fourth cultivation is carried out together with earthing up, which helps preserve moisture, prevent lodging, and drain water to prevent waterlogging. Although sesame has a certain drought resistance, during the seedling stage and flowering stage, if the soil is dry, watering should be carried out. After sesame flowers, it is most afraid of waterlogging. If there is too much soil moisture, a large number of buds and flowers will drop, and in severe cases root rot and death may occur. Therefore, before the rainy season arrives, field drainage work should be done well to ensure that the field dries after rain and is not damaged by waterlogging. Sesame has a long flowering period. The lower capsules are nearly mature, while the upper part is still flowering and fruiting successively, so maturity is very uneven. To make sesame mature more uniformly, concentrate nutrients on the capsules already set, achieve full seeds, and promote early maturity and increased yield, timely topping should be adopted. For the timing of removing the growing tip, single-stem varieties should be treated before growth stops, when the top of the stem just begins to protrude. If topped too early, the number of flowers and capsules is affected; if topped too late, the topping effect is not achieved. Branching varieties can be topped in two operations. The first is to appropriately remove the growing tip of the main stem earlier to preserve branch growth. The second is, before branch growth stops, when the tips protrude, remove the growing tips of the branches. Topping should be done on sunny days, removing small tips, with about 3 cm being appropriate. In addition, attention should be paid to controlling underground pests during the seedling stage and controlling pests such as aphids and sesame hawk moths during the middle growth period.

VI. Seed Retention and Harvest of Sesame

1. Seed retention. Sesame seed retention is mainly carried out in the field. The selection criteria are vigorous and disease-free plants, consistent traits, uniform maturity, low capsule-bearing position, dense and large capsules, strong disease resistance, and other high-yield traits. After selecting plants, they are cut and threshed separately, and the upper and lower capsules are removed. For branching varieties, retain the capsules on the main stem, then dry and thresh separately, using the seeds threshed for the first time as seed.

2. Harvest. Sesame capsule maturity is very uneven, and immature capsules on the plant can undergo after-ripening well. If harvested only after the whole plant matures, the lower capsules will already have split open and the seeds will be lost, so a high yield cannot be harvested well. Generally, the suitable harvest period is when the leaves at the base of the sesame plant have yellowed and fallen, the upper capsules have turned yellow, and the seeds in the middle and lower capsules show the inherent color of the variety. Harvesting too early not only gives low yield, but also the oil content is not high. Sesame is harvested about early September, and summer sesame about mid-to-late September. Timely harvest requires seizing the time and striving to finish within a short period, with morning harvest being best.