Introduction

Manures and fertilisers are limited in supply and are costlier inputs. The maximum benefits should be achieved from such inputs. For this they need to be applied at the proper time and site and by the correct method. If they are applied much earlier than usual they may be lost in various ways and thus use-efficiency may be less than expected. Similarly, if they are not applied at the proper place they may not be properly utilised by the plants and thus the necessary objectives may not be fulfilled. Saving in organic fertiliser is achieved by following ways:

Time of Application

Di-and tri-calcium P fertilisers are generally applied before the preparatory tillage as they require sufficient time to decompose or react or mineralise after thorough mixing with the soil.

Compound and mixed fertilisers and biofertilisers are applied during preparatory tillage to mix thoroughly with the soil.

Straight fertilisers, fertiliser mixtures and the readiy soluble but highly mobile fertilisers, slow-release fertilisers, starter dose of N fertilisers to legume crops and fertilisers for specific nutrient deficient soils are applied during the time of planting or sowing.

Top dressing may be done to the soil or to the foliage highly mobile fertilisers are applied in splits in medium to long duration crops and in light soils. Slow release fertilisers are also applied as top-dressing.

Methods of Application

Use of proper method of application and the in required form helps to save the quantity.

Where there is the problem of fixation, fertilisers are placed in the plough-sole after opening the furrow by the plough. Such furrows are covered immediately during the next run of the plough.

In wet land rice a reduced form of N fertiliser (ammonium sulphate) is placed deep in the reduced layer to avoid denitrification.

P and K fertilisers in small quantities are used along with seeds during sowing. Seed-cum-fertiliser drill is used for contact placement.

Sometimes N fertilisers are pelleted in various types of mudbolls and placed deep into the soft saturated soils of wet and land rice.

Use of starter solution helps for soaking seeds, dipping roots or plants after uprooting ,in nutrient deficient areas starter solutions help the plants in many ways and the mixture with 1:1:1 or 1:2:1 of N,P,K is applied efficiently. Also foliar spray of micronutrients helps to reduce the quantity of individual fertiliser.

Fertilisers containing soluble nutrients are dissolved and diluted with irrigation water and applied either through surface, subsurface or overhead irrigation.

Principles governing selection of proper time and method for application of fertilisers

The time and method for application of fertilisers depends on various factors. The most important are:

• The nature of the fertilisers;

• The soil type and soil-water balance;

• The nature of the crop and the cropping system.

• The nature of manures and fertilisers

Highly and slightly mobile nutrients P and K containing fertilisers should be applied in splits with lower doses or as foliar spray.

The soil type and soil-water balance

In wet soil the loss of N is more. Slow release N fertilisers may be used safely immediately after the establishment of the crop. Ammoniacal fertilisers should be applied in the reduced zone and nitrate fertilisers should be applied in the oxidised zone in wet land rice as top-dressing in splits.

The nature of the crop and cropping system

It is better to apply N fertiliser in two or more splits of the total quantity as per the duration and requirement of the crop, soil type and type of fertiliser. In a very short duration crop, soil type and type of fertiiser. In a very short duration crop, such as leafy vegetables or seedlings in the nursery, the entire does of N may be applied as basal dressing to the soil. In long duration crops such as sugar cane, split application of fertilisers may be adopted. In dryland crops N may be applied along with other manures and fertilisers as basal. In irrigated crops phosphates may be applied to legumes in rotation and N to cereals or other crops. In rain fed or dryland cropping P fertilisers should be applied to the kharif crop while N and K to each crop of kharif and rabi if none of the crops are leguminous.

Doses of Manures and Fertilisers

Plant nutrients are lost or removed from the soil in various ways. For successful cropping season after season, year after year plant nutrients must be replenished in the right quantity, form, place and time. The quantity or dose of fertilisers may be corrective dose, maintenance dose, and productive dose. To determine the optimum dose of nutrients, the soil must be tested to evaluate its initial fertility status. At the same time chemical, physical and biological properties of the soil are to be evaluated as they have contributing roles on nutrient availability. A soil-test crop response method is to be followed to check the soil reaction, moisture and temperature as it affects the responses of nutrients.

Ag.
Technologies
(Crop
Husbandry)