The deficiency of plant nutrients and organic matter in the soil is made up by adding manures and fertilizers to the soil of crop-fields. Both manures and fertilizers are major sources of nutrients of plants, so they are used in crop production. Besides water CO2 and sunlight plants required no. of elements for their growth.
These elements are known as nutrient. Plants get their elements from the salt of these elements present in the soil. But after repeated cultivation of plants soil become poor in these elements. The substance added to the soil to make up the deficiency of the essential elements these by increasing the fertility of soil are called fertilizers.
Qualities of Good Fertilizers 1. The elements present in good fertilizers must be easily available to plants. 2. Good fertilizers must be sufficiently soluble in water. 3. Good fertilizers should contain nothing injurious to plants.
Theory of Chemical Fertilizers The majority of the chemical fertilizer whether simple or mixed are in organic compounds, the generally contain cation likes Ca2+, K+, NH4+ etc. and are soluble in water. Therefore, these can be identified from their aqueous solution by the regular systematic scheme used for qualitative mixture analysis.Analysis of Chemical FertilizersAll the plants need nutrients for their growth but each plant may not require the same kinds, to meet the requirement of particular crop we first need to analyse the soil and then select the fertilizer. This proper selection of fertilizer is possible if we know the cation and anion present in a particular fertilizer.
The analysis means identification of acid and basic radicals present in fertilizers. In general, a chemical fertilizer may contain:Anions : Cl–, NO3–, SO42–, PO43– etc.Cations : Ca2+, K+, NH4+ etc.Manures or natural fertilizers Manures are natural fertilizers. They are bulky sources of organic matter which supply nutrients in small quantities but organic matter in large quantities.
Manures include farmyard manure (FYM), compost, green manures, vermicompost, etc.Advantages of Manures:Manures affect the soil in following three ways : (i) The manures enrich the soil with nutrients. They replenish the general deficiency of nutrients in the soil. Since manures contain nutrients in small quantities, they are needed to be applied in large quantities.
(ii) The manures add organic matter (called humus) to the soil which restores the soil texture for better retention of water and for aeration of soil. For example, organic matter present in the manures increases the water holding capacity in sandy soils and drainage in clayey soil. (iii) The organic matter of manures provide food for the soil organisms (decomposers such as bacteria, fungi, etc.) which help in making nutrients available to plants.
Thus, organic matter help to improve the physical properties of soil, reduce soil erosion, increase the moisture holding capacity of soil and above all these advantages, they are low cost nutrient carriers.Disadvantages of Manures:Manures are bulky with low nutrient content. The nutrients of manures are released slowly, not keeping pace with the high and rapid demand of nutrients by improved high-yielding hybrid varieties of crops. Being bulky and voluminous, they are inconvenient to handle, store and transport.
Moreover, a manure is not nutrient specific and hence it is not much useful when a particular nutrient is required in the soil for a particular crop.Types of Nutrients1. Farmyard Manure (FYM) : FYM is the decomposed mixture of cattle excreta (dung) and urine along with litter (i.e., bedding material used in night under cattles) and left over organic matter such as roughage or fodder.
These waste materials are collected daily from the cattle shed and stored in a pit for decomposition by the microbes (bacteria, fungi, etc.). FYM contains nitrogen, phosphorus and potassium. Thus, a well decomposed farmyard manure contains about 0.
5 percent nitrogen (N), 0.2 percent phosphorus pentaoxide (P2O5) and 0.5 percent potassium monoxide (K2O).2. Compost :Compost is prepared from farm and town refuge such as vegetable and animal refuse (e.
g., excreta of domestic animals such as cattle, goat, sheep, horse, donkey, camel, dogs, cats, etc.), faecal matter of human beings, sewage waste (Box 7-2), weeds, crop stubble, straw, rice, hulls, forest litter, etc. Composting is a biological process in which both aerobic (organisms requiring the presence of oxygen for the respiration) and anaerobic (organisms, in which respiration takes place in the absence of oxygen) microorganisms decompose the organic matter.
It takes about 3 to 6 months for decomposition of organic refuse. The nutrient contents of farm compost and town compost are not the same. For example, farm compost generally contains about 0.5 percent nitrogen (N), 0.15 percent phosphorus pentaoxide (P2O5) and 0.5 percent potassium monoxide (K2O), whereas compost prepared from town refuse (garbage and night soil) contains about 1.
4 percent nitrogen (N), 1.0 percent phosphorus pentaoxide (P2O5) and 1.4 percent potassium monoxide (K2O).Method of Preparing Compost : For the preparation of compost, a trench of suitable size 4 to 5 m. long, 1.5 to 1.
8 m. broad and 1.0 to 1.8 m.
deep in dug. A layer of well-mixed refuse of about 30 cm. thickness is spread in the trench. This layer is well moistened by slurry (water paste) of cattle dung and water or earch and water. A second layer of mixed refuse is spread in trench till the heap rises to a height of 45 to 60 cm. above ground level.
The top of this heap is then covered with a thin layer of mois earth. After three months, the partially decomposed biomass is taken out of the trench and collected in conical heap. This heap is moistened if necessary and covered with earth. After another one or two months, the compost is ready for use in the field.3. Green Manuring :The practice of green manuring includes growing, turning or ploughing and mixing of green crops with soil to improve physical structure and soil fertility.
Green manures may include both leguminous and non-leguminous plants, e.g., Sannhemp (Crotalaria juncea), Egyption clover (‘Berseem’, Trifoliumalexandrium), Sesbania or ‘Dhaincha’ (Sesbaniaaculeata) and cluster bean or ‘Guar’ (Cyamopsistetragonoloba). These plants are used by Indian farmers to add nitrogen and organic matter to the soil for the improvement of crop yield. The green manure crops are grown in the field for about 6 to 8 weeks and turned into field in the tender stage, i.
e., at flowering stage. These crops remain buried for about one to two months. During this period, plants should be completely decomposed before sowing of next crop.
Generally the crops which require high nutrient input, are raised in the green manured field. Such crops are rice, maize, sugarcane, cotton, wheat, etc.
