Introduction

A mature ovule having embryonic plant, food substance, and protective cover or germ which can be used in sowing or planting to produce crop is known as a seed. Production of the seed depends on the quality of the seed. For the high production of quality seed, it is important to maintain the varietal characteristics of seed and to control seed-borne diseases. This article emphasis on giving knowledge to the farmers about technical wheat cultivation and support for the improvement of quality seed production.

Wheat rank as the third important food crop in Nepal after rice and maize. Wheat is grown in all three domains of the country, ranging from sea level to 4000m. It is grown in 0.7 million hectares with a total production of 2.0 million metric tons and the productivity is about 2.85 ton/ha (Krishi dairy 2076/77). Wheat also shares about 7.14 % in national agriculture gross domestic product (AGDP). Lower productivity of high yielding and improved varieties of wheat is due to a lack of scientific knowledge on the use of fertilizers, insecticides, irrigation. The quantity of wheat that was imported in Nepal is 170 thousand tons in 2019 and there are 35 improved wheat cultivars, 540 landraces, and 10 wild relatives of wheat.

Wheat is a winter season crop. The optimum temperature for seed germination, growth, and development is 20-25. The rainfall requirement of wheat in Nepal has been estimated at 1300-1850mm. It is a long day plant, so it requires a photoperiod of above 12 hours. Soil having neutral PH and optimum organic matter content is good for wheat cultivation.

Seed Production :

Good land preparation helps in improved germination, good stand establishment, and destruction of potential weeds. One deep ploughing with soil turning plough followed by two harrowing and planking immediately before sowing produces a good, firm seedbed that is desirable for timely cultivation and conservation of moisture.

Healthy and certified seeds that have germination capacity of about 85 %, moisture content 12%, and physical purity 98 % and seed which is brought from an authorized dealer with tag should be selected for sowing. Seed should be treated with a fungicide like Vitavex or Thiram or Agrosan GN @ 2.5 gm/kg of seed. Healthy seeds are stored and treated with Cerason or Agrosan GN @ 2.5 gm/kg of seed.

Sowing time for the hilly region is mid of October and for the Terai region in mid of November. Usually, a seed of 100 kg/ha is recommended under the favorable condition of normal sowing and 125-150 kg/ha for late sowing. Recommended spacing for line to line is 20-25 cm and plant to plant is 5-8 cm. There are different sowing methods; broadcasting, sowing behind the plough, drilling, and dibbling.

Farmers can apply manures up to 10 ton/ha before land preparation in wheat crops. The recommended dose of fertilizer NPK for maximum yield is 100:20:60 kg/ha. 15-20 kg/ha ZnSo4 at basal once in a year but if zinc deficiency occurs it can be corrected by the foliar spray of 15% ZnSo4 + 2.5% Ca(OH)2. Wheat usually requires 4-6 irrigation but the most critical stage is the crown root initiation stage (20-25 days after sowing) and heading stage.

Several weeds are associated with the harmful effect on wheat crops. Weed can be managed manually, mechanically, or by chemical method. Manual or mechanical methods for the wedding are done at 20-40 days after sowing. The most common weed of wheat are Philaris minor (ragadhey jhar), broadleaf, narrow-leaf which can be controlled by the application of a mixture of Isoproturon (500 gm/ha) + 2,4-D (125g/ha).

Adequate and timely roughing is extremely important in quality seed production. Roughing refers to the removal of undesirable plants from the seed production plots. In wheat, the crop should be rouged twice at heading and maturity because off-types and other varieties of the same species are most easily identified.

Since wheat is a self-pollinated crop, an isolation distance of 3 meters is recommended and the seed crop is inspected twice, once at the flowering stage, and once at the maturity stage. The objective of field inspection is to ensure that specific standards for raising a seed crop have been met including isolation and to ensure relative freedom from weed species, seeds of other distinguishable varieties, and diseases infected pests.

The major diseases of wheat are rust (yellow, black, and brown), loose smut, and bacterial leaf blight. Among these most major diseases is yellow rust. We can control these diseases by cultivating disease resistant varieties and by using the recommended dose of NPK as well as by spraying fungicide like Mancozeb and by treating the seed with the chemical before sowing. Major insects, pest of wheat are white grub, armyworms, wireworms, aphid which can be controlled by adopting crop rotation, using pesticides like Dimethioate, Spinosad as well as doing soil treatment by Malathion.

The crop should be harvested when the grains become hard and the straw becomes yellow, dry, and brittle. Harvesting is done by serrated sickle, brush cutter, or reaper. Threshing is done by trampling, peddle thresher, or thresher machine. Harvesting and threshing can be done by a combine harvester also. Then processing of seed is required which includes drying, cleaning, packaging, and storage. Drying is the process in which the moisture content is reduced to 12% for seed production and grain purpose to 10-12%. Cleaning is done for the separation of dust from seeds. The packaging is done in an airproof bag like super grain bags. Finally, seed is tagged and labeled with all the details like crop name, variety, class of seed, lot number, quantity, date of test, purity percentage, inert matter percentage, germination percentage and other necessary information.

Conclusion :

Thousands metric tons of quality seed is imported from India annually causing billions of Nepalese currency being exported to India. Very promising wheat varieties like Gautam, Vijay, Munal, Khajura Duram- 1, -2 and others have been released by NARC but during the main season of wheat cultivation, farmers are compelled to face the same problem of lack quality seed in the market. Seed production system should be strengthened by involving local farmers in the seed production. Seed production should not be confined to research station and seed company farm only but it should be also done in farmers field with the participation of local farmers facilitated by extension officer and research scientist. Different programs for educating and training the farmers about quality seed production should be conducted and farmers should be encouraged to produce seed rather than just grain. Timely availability of others inputs like fertilizer, insecticide and pesticide also play a key role in the production of quality so the timely availability of all the necessary inputs should be managed by concerned authority.