Seeds and Sowing PDF

Agron -113 Seeds and sowing Lecture 2 CROP: Crop refers to plants sown and harvested by man for economic use. When plants of a particular species are grown together on a piece of land for certain economic purpose, the...

Agron -113 Seeds and sowing Lecture 2 CROP: Crop refers to plants sown and harvested by man for economic use. When plants of a particular species are grown together on a piece of land for certain economic purpose, they are called crop. VARIETY: Variety is a group of similar plants which by structural features and performances may be identical from other varieties within the same species. Varieties are sometimes known as ‘Cultivars” which means cultivated varieties. E.g. rice crop has several varieties viz. Ranjit, Pankaj, Joymoti, Kanaklata, IR-36 etc. They have different characteristics regarding duration, height, tillering, grain quality and yield. Selection of a variety depends on several factors, such as Yield potential Quality to satisfy consumer preference. Resistance to major pest and disease. Environmental adaptability Yield stability Duration SEED: Botanically a seed is a fertilized ripened ovule. It is a part of a flowering plant that contains the embryo and develops into a new plant if sown. Plant propagation is made in two ways, Sexual (by seeds) and asexual (by vegetative means). Biologically, seed is a ripe, fertilized ovule and a unit of reproduction of flowering plants. Agronomically, a seed or seed material or prapagule is the living organ of the crop in rudimentary (undeveloped) form that is used for propagation. Or In other words any part of the crop from which a new crop will grow. E.g. true seed, stem cuttings, rhizome cutting, bulbs, tubers etc. Crop stand establishment Good crop establishment is one of the most important features in better crop production. The better crop establishment is in turn expressed as optimum plant population. Number of plants per unit area in the cropped field is called as plant population. Optimum plant population It is the number of plants required to produce maximum output or biomass per unit area. Importance of plant population Yield of any crop depends on final plant population The plant population depends on germination percentage and survival rate in the field. Under rainfed conditions, high plant population will deplete the soil moisture before maturity, where as low plant population will leave the soil moisture unutilized. When soil moisture and nutrients are not limited, high plant population is necessary to utilize the other growth factors like solar radiation efficiently. Under low plant population, individual plant yield will be more due to wide spacing. Under high plant population, individual plant yield will be more due to narrow spacing leading to competition between plants. Yield per plant decreases gradually as plant population per unit area is increased, but yield per unit area increases up to certain level of population. That level of plant population is called as optimum population. So, to get maximum yield per unit area, optimum plant population is necessary. Agron -113 Seeds and sowing Establishment of good crop stand is the essential pre-requisite for attaining high yield. It depends on Good quality seed Proper tillage Time of sowing Seed rate Depth of sowing Method of sowing / planting Good quality seed Quality seed ensures a uniform crop stand. Ecological conditions such as temperature, precipitation and sunshine cannot be controlled by a farmer. But he can choose a good quality seed. The yield of a crop will not be as good as expected if poor quality seed or variety is used. Quality of a good seed should be - The seed should be genetically pure and true to type It should be healthy, well developed and uniform in size It should have strong germination capacity and should give vigorous seedlings It should be free from seed borne diseases and insect pests It should be free from other crop seeds, weed seeds, dirt and inert materials It should be dry and not mouldy and should contain 12-14% moisture Advantages of using good quality seeds Uniform germination thus avoiding replanting, gap filling Vigorous seedling growth, which reduces weed and disease Uniform growth stages, maturity and products High return per unit area as the genetic potentiality of the crop can be fully exploited Maintain good quality under storage conditions The quality seed respond well to the applied fertilizers and nutrients High produce value and their marketability Proper tillage Proper tillage is necessary for better seed -soil contact. Type of tillage depends on the soil type, seed size and rooting pattern of the crop. Deep tillage is required for sugarcane & other deep rooted crops, fine tilth for small seeded crops like Chilli, coriander, Sesamum, mustard etc. and rough tilth for large seeded crops. Time of sowing Optimum time of sowing is important to get proper germination and plant stand of the crop. Time of sowing for each of the crop for each of the agro climatic zones of the country is determined depending on the climatic factors like temperature, rainfall, sunshine hours etc. Sowing crop at optimum time increases the yields due to suitable environment at all the growth stages of the crop. Different growth phases of the crop should coincide with optimum weather conditions. Under the conditions of early or delayed sowing, a good crop stand may not be observed due to poor germination and growth of the crop. Seed rate It means the quantity of seed or seedlings or other propagating materials needed to achieve a pre- determined level of plant density per unit area. Seed rate determines the final plant population density in a field. Too high or too low than the recommended seed rate affect the plant population and then yield of the crop e.g. higher seed rate will influence higher plant population per unit area. It results in heavy competitions within the crop plants and suppresses the crop growth. Lower seed rate will result lower plant population thereby lowers the yield per unit area. Therefore, an optimum seed rate leads to higher yield. Seed rate of different crops and variety may vary depending on weight of the seed, spacing requirement, germination percentage and purity percentage of the seeds. Agron -113 Seeds and sowing Depth of sowing The distance from true soil surface to the underground position of seed sown or to be sown denotes the depth of sowing. Optimum depth of sowing mainly depends on seed size, coleoptiles length and soil conditions viz., soil texture, structure, moisture content of the soil. Optimum depth of sowing for most of the field crops ranges from 3 to 5 cm. If the seed is placed in more depth, it will take more time for germination and emergence and sometimes the seed may not emerge from soil. If the seed is placed in a shallow depth, the surface soil dries up soon and germination may not take place. Again the seeds may be taken away by birds, rodents, insects etc. these may lead to poor germination and crop will be with large number of gaps. In this situation weed problems become serious. Uneven depth of sowing results in uneven crop stand with plants of different height, age and size with uneven maturity and finally harvesting becomes a problem. Bold seeded crops such as maize, chickpea, and groundnut can be sown deep (up to 10 cm). Small seeded crops like mustard, Sesamum should be sown at a shallow depth of 3-5 cm. Method of sowing / planting Sowing is the placing of specified quantity of seeds in the optimum position of soil for germination and growth. Most of the field crops and vegetable crops except tuber and root crops are usually grown by sowing of seeds. Planting is usually referred to placement of seedlings, cuttings, tubers, rhizomes, slips etc in the seed bed for crop establishment. When seedlings are raised in separate nursery beds and later planted in the main field at appropriate age of the seedlings, the term transplanting is used. Different methods of sowing : I. Broadcasting or direct sowing II. Drilling III. Dibbling IV. Transplanting V. Putting seeds behind the plough BROADCASTING: Broadcasting is a method of sowing where seeds are scattered or spread as uniformly as possible over a well prepared land which may or may not be incorporated or covered with soil. It is the primitive method of sowing, suitable for close planted crops like wheat, paddy, Sesamum, coriander etc. It is an easy, quick and low cost method. In this method number of plants per unit area is more important than that of definite spacing from plant to plant. Disadvantages: Poor crop establishment Uneven distribution of seed Uneven depth of sowing as a result at any given time, plants are at different height, size and age. Proper spacing can not be maintained More seed rate is required Covering and compaction is not proper, so losses from the birds and rodents are more. Proper intercultural operations like weeding, earthing up is not possible. Fertilizer application, spraying of agrochemicals is difficult. DRILLING: Drilling is a practice of placing or dropping seeds in furrows or lines. In this method furrows of predetermined dimension are prepared. Seeds are dropped at a definite depth and distance. Then the furrows are covered with soil and compacted for better seed soil contact. It can be done manually and seed drill or seed cum fertilizer drills are used. Seeds are also sown by dropping behind the plough and using a funnel like attachment with a tube behind the plough called ‘pora’. Agron -113 Seeds and sowing Advantages: It maintains a uniform plant population per unit area. Uniform spacing and depth of sowing results in uniform emergence and even crop stand. Weeds can be managed economically and efficiently by using tools and implements. Seed requirement is considerably reduced. Spraying of agrochemicals, application of irrigation and other intercultural operations become easier. Mulching can be done in between the rows for reducing evaporation loss to conserve moisture. Disadvantage: It requires more time, labour and energy. Cost is high Drill machine is required for sowing in large scale. DIBBLING : This is a method of putting a seed or a few seeds or seed materials in a furrow hole or pit made at a predetermined spacing and depth with a dibbler or planter or very often by hand. This method is suitable for widely spaced crops which require specific geometric area for their canopy development. Seeds are dibbled in levelled field or on ridges, pits or pockets. The entire field need not be prepared for sowing. Only the seeding zone is prepared. This method is suitable for crops like cotton, maize, castor, potato, sugarcane etc. Advantages- An intercrop can be taken in wider spaced crops Implement is not required for sowing Optimum plant population can be maintained Seed requirement is less than other methods Disadvantages- Laborious & time consuming Only high value & bold seeded crops are sown Require more labour, hence increases the cost of cultivation TRANSPLANTING: Transplanting is the removal of an actively growing seedling from one place or nursery bed and planting in the main field for further growth till harvest. Proper care is taken in the nursery bed such as fertilization, spraying of fungicide and insecticide, weeding etc. when the seedlings develop 3-4 leaves or after 3-4 weeks, they are pulled out from nursery and transplanted in the main field at proper spacing and depth. Advantages: Proper management of young seedlings under compact area /nursery is easy. It reduces cost of irrigation water and pest and disease management during the early stages. It increases the scope of multiple cropping in the main field by reducing the duration of the crop in the main field, thus cropping intensity can be increased. E.g. rice, chilli, brinjal, tomato etc. PUUTING SEEDS BEHIND THE PLOUGH: It is dropping of seeds behind the plough in furrows with the help of manual labour by hands. This method is followed for crops like gram, soybean in some areas for better utilization of soil moisture. The seeds are covered by successive furrow opened by the plough. This method is not commonly followed for sowing of the crops. Difference between Dibbling and Broadcasting Sl. No. Dibbling (Line sowing) Broadcasting (Random sowing) 1 Costlier Cheaper 2 Takes considerable time Quickest and time saving 3 Fixed seed rate Higher seed rate 4 Mechanization is possible e. weeding, harvesting Not possible 5 Uniform utilization of resources (land, water, light, nutrient Resource utilization un-uniform etc.)