Contents
Evolutionary Biology Topics allow us to trace the history of life on Earth.
What is Selection of Seeds and Sowing of Seeds?
Once the soil in the field has been prepared by ploughing, levelling and manuring, etc., seeds of the crop can be sown in it. The process of scattering seeds (or putting seeds) in the ground soil for growing the crop plants is called sowing.
Sowing is the most important part of crop production. Before sowing, good quality seeds are selected. Good quality seeds are clean and healthy seeds free from infection and diseases. Farmers prefer to use seeds which give high yield of food grains.
Selection of Seeds
Activity 1
We can select good, healthy seeds for sowing as follows : Put all the seeds in a bucket containing water and stir well. Most of the seeds will settle down at the bottom whereas some seeds will float on top. The seeds which sink at the bottom of the bucket are the healthy seeds. On the other hand, the seeds which float on water are the spoiled seeds.
This can be explained as follows : Healthy seeds are heavy, so they sink in water. The seeds which have been partially eaten by pests or damaged by disease become hollow and light, and hence float on water. The seeds may also be treated with fungicide solutions before sowing to prevent the seed-borne diseases of crops.
Methods of Sowing Seeds
Seeds are sown in the soil either by hand or by seed drill. Thus, there are two methods of sowing the seeds in the soil. These are :
- Sowing by hand, and
- Sowing with a seed drill.
The sowing of seeds by hand (or manually) is called broadcasting. In the sowing with hand or manually, the seeds are taken in hand and gradually scattered in the entire ploughed field. This method is, however, not very good because there is no proper spacing or proper depth at which the seeds are sown by hand. Moreover, the seeds scattered on the surface of the soil for sowing can be picked up and eaten by the birds.
The implement used for sowing is a seed drill. A seed drill is a long iron tube having a funnel at the top (see Figure). The seed drill is tied to back of the plough and seeds are put into the funnel of the seed drill. And as the plough makes furrows in the soil, the seeds from the seed drill are gradually released and sown into the soil furrows made by the plough.
Thus, by using a seed drill for sowing, the seeds are sown at the correct depth and correct intervals (or spacings). The seeds sown with a seed drill are in regular rows. Moreover, when the seeds are sown in furrows by a seed-drill, the seeds get covered by soil. Due to this, these seeds cannot be picked up and eaten by the birds. It is obvious that the sowing with seed-drill is much better than sowing by hand. A bullock driven seed-drill has just one long iron tube with a funnel.
The tractor driven seed-drill has 5 to 6 iron tubes joined together with a common funnel at the top (see Figure). When the seeds are put into the funnel of such a seed drill, the seeds are released through all the tubes and get sown into 5 or 6 furrows of soil simultaneously.
By using such tractor driven seed-drills, the sowing of seeds can be completed quickly. Most of the crops like wheat, gram (chana), maize and millet etc, are grown (or cultivated) by sowing the seeds directly into soil.
Precautions for Sowing Seeds
The following precautions should be taken while sowing seeds in the soil.
(i) The Seeds Should be Sown at Right Depth in the Soil Suitable For Germination :
If the seeds are just spread on the surface of the soil, then the seeds will be eaten up by the birds. And if the seeds are sown too deep, then they may not germinate because they cannot breathe (cannot get sufficient air) at greater depth. So, the seeds should be sown at right depth in the soil which is suitable for germination. This right depth is learnt by experience.
(ii) The Seeds Should be Sown at Right Intervals or Spacings :
The seeds should neither be placed too close nor too far apart. This is because if the seeds are sown too close, then plants formed from them will also be too close, and will not get enough sunlight, water, and other nutrients. Thus, an appropriate distance between the seeds is important to avoid overcrowding of plants. This allows the plants to get sufficient sunlight, nutrients and water from the soil. On the other hand, if the seeds are sown too far apart, then it will be a wastage of field space.
(iii) The Seeds Should Not be Sown in a Dry Soil :
Moisture in the soil is necessary for the germination of seeds. So, if seeds are sown in a dry soil, they may not germinate at all.
(iv) The Seeds Should Not be Sown in a Highly Wet Soil :
If the seeds are sown in a highly wet soil, then on drying, the soil surface becomes hard and because of this hard surface of soil, the germinating plumule will be unable to come out of ground. Moreover, the seeds are not able to respire properly due to lack of air under these conditions of hard surface of soil.
Advantages of Sowing with a Seed Drill
The sowing of seeds with a seed drill has the following advantages :
- By using a seed drill for sowing, the seeds are sown at correct depth and correct intervals (or spacings).
- The seeds sown with a seed drill are in regular rows.
- When the seeds are sown in furrows by a seed drill, the seeds get covered by soil and hence these seeds cannot be picked up and eaten by birds. This prevents damage caused by birds.
- Sowing by using a tractor-driven seed drill saves time and labour.
Transplanting (or Transplantation)
Though most of the crops are grown by sowing the seeds directly in the soil but in some crops like paddy (rice) and many vegetables, the seeds are not directly sown in the soil in large fields. In the case of crops like paddy (rice) and vegetables like tomatoes and chillies (mirch), the seeds are first sown in a small plot of land or nursery and allowed to grow into tiny plants called seedlings by providing them with a good dose of nutrients.
After the seeds have grown into tiny plants called seedlings in the seed-bed or nursery, only the healthy and well developed seedlings are then picked out from the nursery bed and transferred or transplanted to the regular field. The process of transferring the seedlings from the nursery to the main field by hand is called transplantation or transplanting.
During transplantation, proper distance is kept between the various seedlings and also between the various rows of seedlings, to enable each and every plant (formed from seedlings) to get sufficient sunlight, water and other nutrients for normal and healthy growth (see Figure).
The process of transplantation gives us many advantages over the direct sowing which ultimately leads to an increase in the yield of the crop. The various advantages of the transplantation process are given below :
- The process of transplantation enables us to select only the better and healthy seedlings for the cultivation of crops. The bad seedlings can be rejected. This selection is, however, not possible when the seeds are directly sown in the soil.
- The process of transplantation allows better penetration (deeper penetration) of the roots in the soil.
- The process of transplantation promotes better development of the shoot system of plants.
- The process of transplantation allows the seedlings to be planted at the right spacings so that the plants may get uniform dose of sunlight, water and nutrients.
The practice of transplantation is used in the cultivation of paddy crop (rice crop) and in the cultivation of many vegetables like tomatoes and chillies. We will now discuss manures and fertilisers.