Agronomic Principles PDF

**AGRONOMIC PRINCIPLES** The seed production of varieties and hybrids should be carried out carefully in the region where these are well adopted. For example, seed production of cabbage is only possible in dry temperate areas where chilling requirements are met. The climatic factors have direct bea...

**AGRONOMIC PRINCIPLES** The seed production of varieties and hybrids should be carried out carefully in the region where these are well adopted. For example, seed production of cabbage is only possible in dry temperate areas where chilling requirements are met. The climatic factors have direct bearing on the quality seed production. Climate is the most important factor and generally for seed production, dry temperate climate is most suitable. Different vegetables need different climate for successful seed production and can be classified into temperate and tropical type. Climate may enhance bolting in the normal bulb crop of onion. Photoperiod also affects bulb crop and seed production in onion. Like climatic factors, the production and post harvest technologies will also plays a major role in quality seed production. Hence, proper strategies to be planned for quality seed production especially in horticultural crops particularly in vegetable seed production. **Selection of suitable agro-climatic region:** 1. A crop variety should be grown in the adapted areas in terms of photoperiod and temperature. 2. The sensitive varieties should be grown in their specific localities 3. Regions with moderate rainfall, humidity and temperature more suited 4. For effective pollination, prevalence of moderate rainfall and wind is much suitable 5. Flowering should coincide with dry sunny period Land selection: --------------- The seed production land should be selected mainly for following reasons; 1. 2. 3. Secondly for ------------ 1. 2. 3. 4. **In general the land must be** - Free from volunteer plants, weed plants and other crop plants. - In the preceding season the same crop should have not been grown. - Avoid areas where isolation is a problem. - Avoid coastal belts and marshy places. - Avoid areas of endemic diseases and pests. - Select compact areas for hybrid seed production. - Availability of skilled labourers especially for hybrid seed production. - Fields near the processing operations with transporting facilities and marketing facilities are most suitable. **Selection of seed** **The seed must be from authenticated seed source and appropriate class of seed must be used for further multiplication. Eg. For production of foundation seed breeder seed must be used.** Proof of purchase (bill) is necessary to identify the source along with the following details. Details on the tag v*iz.,* name of the agency, purity, germination, validity period. C.S - F.S **Isolation** Art of keeping the seed parent from the contamination both genetic and physical contaminants **Isolation of seed crops** **Isolation distance:** **Distance maintained between the seed crop and source of contaminant** **Isolation distance depends on** 1. **Pollination behaviour** 2. **Pollinating agents** 3. **Pollen viability** **Types of isolation** - Physical or distance isolation -- expression is in meters. - Time isolation - Raising the crop by staggered sowing so that synchronization of flowering and pollination in seed crop can be achieved and the contamination is prevented. Normally one month is the time isolation given for agricultural crops but not in crops having indeterminate growth. - Barrier isolation -- if the above said isolation is not possible we can go for barrier isolation by erecting tall shelter trees. - Physiological isolation -- differ in flowering due to change in altitude. Factors influencing isolation distance ====================================== 1. Pollination behaviour of crop - Self -- pollinated crops require less isolation distance (ie) 3m -- 50 m. - Often cross pollinated crop 100 -- 400. - Cross pollinated crop require 800 -- 1600 m. 2. Pollinating agent whether wind (or) insect. If wind - Direction of flow of wind - Wind velocity If insect ========= - Flight capacity of insect - Stickyness of pollen to insect legs. 3. Pollen characters - Viability of pollen. - Pollen production capacity crop. - Weight of pollen. - Nature of pollen whether having serrated edge or blunt edge. - Time of anthesis. 4. Presence of wild pollinators -- (eg) wild bhendi 5. Designated disease 6. Whether is var. or hybrids -- in general vars. Require less I.D than hybrids. 7. If variety whether it is an inbred, composite or synthetics. -- inbreds require more isolation distance than varieties. 8. If hybrids type of hybrid whether it is single cross hybrid or double cross. Single cross required more I.D. when compared to double cross. 9. Breeding mechanism of plant detasseling or sterility or emasculation and dusting, emasculation and dusting method require less I.D compared to sterility or detassel methods. 10. Stages of seed production - B.S - more I.D. - F.S - less I.D compared to B.S - C.S - less I.D compared to B.S & F.S because of the genetic purity. **Pre-sowing treatment** - Seeds should be appropriately treated. Pre-sowing seed treatments with nutrients. The following points should be considered. - Duration of soaking - Soaking water to seed ratio. - Old seed or new seed. - Quantity of micro, macro nutrients or growth regulators. - Seed hardening with different chemicals. **Seed treatment to break dormancy** Dormancy is an endogenously controlled but environmentally imposed temporary suspension of growth accompanied by reduced metabolic activity and relatively independent of ambient environmental condition. Types of dormancy ================= +-----------------------+-----------------------+-----------------------+ | **Type** | **Cause** | **Treatment** | +=======================+=======================+=======================+ | ### Endogenous dorman | | | | cy | | | +-----------------------+-----------------------+-----------------------+ | Physiological | Physiological | Warm and / or cold | | | inhibiting mechanism | stratification | | | (PIM) of germination | | +-----------------------+-----------------------+-----------------------+ | Morphological | Under developed | Appropriate | | | embryo | conditions for embryo | | | | growth / germination | +-----------------------+-----------------------+-----------------------+ | Morpho-physiological | PIM of germination | Warm and / or cold | | | and under developed | stratification | | | embryo | | +-----------------------+-----------------------+-----------------------+ | ### Exogenous dormanc | | | | y | | | +-----------------------+-----------------------+-----------------------+ | Physical | Seed (fruit) coats | Opening of | | | impermeable to water | specialized | +-----------------------+-----------------------+-----------------------+ | Chemical | Germination | Leaching | | | inhibitors | | +-----------------------+-----------------------+-----------------------+ | Mechanical | Woody structures | Warm and / or cold | | | restrict growth | stratification. | +-----------------------+-----------------------+-----------------------+ Treatment of break dormancy =========================== 1. **Scarification** Any treatment, physical or chemical that softens the seeds coat is known as scarification. - - - - - 2. **Temperature treatments** - - - 3. **Leaching or water soaking** 4. **Light treatment** Lettuce, irradiance of lettuce seeds with either red light (660 nm) or so called white light is essential for germination to occur. In such cases seeds are placed under red light initially and then germinated in dark or they may be germinated under continuous white light. 5. **Exogenous application of growth regulators or chemicals** - - - - - Chemicals which break dormancy ============================== - - - - -