Each of these organic fertilizers can be discussed in brief and then the overall picture of their effect on the yield can be elaborated.
Peat: Peat is a brown coloured substance which comprises of partially decomposed vegetable matter accumulating on boggy or acidic grounds. It helps to enhance the soil through airing and absorbing water.
Animal source: The products obtained as remains from the slaughter houses such as blood meal or bone meal form excellent fertilizers from organic sources. Chicken litter which is a mixture of chicken manure and sawdust has been proved to increase the yields on cotton fields by about 12% over those fertilized with inorganic fertilizer.
Plant source: This include seaweed extracts, humic acid, compost, natural enzyme digested proteins, feather meal or fish meal. Decomposing green manure is also an excellent source of fertility.
Inorganic fertilizers which are ammonia and other chemical-based are great for providing nitrogen to the soil but at the same time have adverse effects on the environment in general. Organic soil fertilizers score over the inorganic fertilizers due to their very nature of formation. They occur either naturally or are formed through natural biological processes. Hence, they are the ones which contribute to the green movement. They confer several benefits to the plant, foremost being they cause no harm to the plant.
With regards to crop growth, this type of soil fertilizers are better than inorganic ones though it is needed in larger amounts as compared to the other. But the fertilizers of the organic variety go to the root of the problem as the essential nutrients present in them are absorbed by the soil more slowly turning out crops which are richer and better than those obtained by using the inorganic fertilizers. With continuous use of such naturally formed fertilizers, the soil is enriched to give greater yields during every harvest season.
This fact is corroborated by an agricultural field experiment undertaken in Sweden which lasted for about 32 years. In the study emphasis was placed on various aspects of soil quality and application of fertilizer in the study treatments was done at rates so as to obtain comparable yields. In the course of the study it was found that use of organic soil fertilizers enhanced the rate of crop yields by 15%. The yield rate produced by the organic variety fertilizer was an astounding 65% whereas that of the inorganic fertilizer was only 50%.