BIOFERTILISERS

The atmosphere contains about 78% nitrogen. Some of the microorganisms found in the soil fix atmospheric nitrogen and convert it into a form that can be early absorbed by plants. Some of the microbes that are commonly used in paddy cultivation for the purpose include azotobacter, azospirillum and phosphobacteria. They not only reduce the cultivation cost of using chemical fertilizers but also increase the yield and improve the fertility of the soil.

Plant growth regulators

Panchagavya

This is a growth regulator produced from a combination of five products obtained from the cow fermented along with a few other bioproducts. For coarse varieties, one spray of 3% panchagavya should be given during tillering and bootling stage.

For fine varieties, one spray of 3% panchagavya should be given during the bootling stage. Amirthakaraisal About 1,250 litres of amirthakaraisal should be mixed with irrigation water for a one-hectare crop. When it is used as a spray, 25 litres are required. This improves the soil fertility and gives good yield.

Green manure

These crops are generally cultivated in the field before cultivating the main crop. They are ploughed into the soil before flowering. Green manure is an essential organic manure for paddy. Plants belonging to the family Leguminosae are commonly used for the purpose. These plants absorb atmospheric nitrogen with the help of certain microorganisms found in their root nodules and convert it into a form which can be used by the plants. These plants should therefore be cultivated before the main crop.

Method of application

Green manure plants such as sunhemp, daincha, Indian indigo should be planted before the paddy season. They should be ploughed into the soil 45–50 days after sowing. The plants should be allowed to decay in the water for ten days and then ploughed.

Uses of green manure

Cultivation of green manure plants between two cropping seasons prevents soil erosion from rain and wind. As the plants decompose they convert unavailable forms of calcium, phosphorus and micronutrients present in the soil into a form that can be easily absorbed by the plants.

In clayey soils, these plants help in increasing the soil's porosity by loosening its particles. They aid in enhancing the aeration and infiltration capacity of the soil. When green manure plants are ploughed into the soil, they decompose and increase its carbon as well as its humus content. These plants are also cultivated as trap crops and for fodder.

Commonly used green manure plants

Sunhemp (Crotalaria juncea), daincha (Sesbania cannabina), Sesbania (Sesbania speciosa), Wild indigo (Tephrosia purpurea), Indian indigo (Indigofera tinctoria), Tephrosia noctiflora.

Green leaf manure : It is a common practice among farmers to plough in the green leafy twigs of certain plants into their fields. The leaves used for this purpose are termed as green leaf manure.

Uses of green leaf manures

The leaves of these plants are used both as green leaf manure and in the preparation of certain biopesticides. They help to increase the nitrogen content of the soil and minimize expenses towards pest management.

Commonly used green leaf manure plants

Azadirachta indica, Pongamia pinnata, Morinda pubescens are some of the commonly used green leaf manure plants. The siris tree (Albizia lebbeck), the gigantic swallow wort (Calotropis gigantea), spotted gliricidia (Gliricidia sepium), Tanner's cassia (Cassia auriculata) and white gulmohar (Delonix elata) are other green leaf manure plants.

Oil seed cake

The pith left behind after oil extraction is commonly called oil seed cake and it is a good source of organic nitrogen. There are different kinds of oil seed cakes available such as groundnut cake, neem seed cake and castor seed cake. Generally, neem and groundnut cakes are used for paddy. They supply the paddy crop with the nitrogen that is essential during its initial growth. The quantity needed is given below.

Updated on : Dec 2014