The traditional alternatives for chemical fertilizers are the non-synthetic, organic fertilizers such as green manure, animal dung and compost manure prepared either on a domestic or industrial scale.
There are several advantages of organic fertilizer than chemical fertilizers in agriculture. Soil structure is improved and as a result the soil’s ability to hold onto water and nutrients increases. Synthetic fertilizer consists of chemical molecules without carbon. These molecules can sometimes be disruptive and are not accessible to microbes. On the other hand, organic fertilizer is rich in organic matter, which helps microbes thrive. Organic fertilizer contains carbon as part of its chemical makeup; and it is the carbon, along with nitrogen, phosphorus and potassium that feeds microbes and enables them to make nutrients available for plants in a naturally occurring biological process. Synthetic fertilizers runoff into the waterways and it is harmful for the water quality and ultimately caused to ecosystem health. Organic fertilizers do not run off as easily (if at all) and are associated with soil structure. According to the Organic Trade Association, organic fertilizer also increases species biodiversity by 30% compared with synthetic fertilizer. Some synthetic fertilizers can cause plant damage to leaves and roots. This is less likely with organic fertilizers.
However, such alternatives are bulky and not very attractive to farmers used as chemical fertilizers. Their transport, storage and field application would require additional labor, time and cost. Organic fertilizers also need time to decompose and provide nutrients to the targeted crop plants and this is not compatible with short term crops. (Kulasooriya, Seneviratne and Ekanayake,unpublished) The level of nutrients present in organic fertilizer is often low. In addition, the nutrients are usually complexes in organic chemical structure. Microorganisms are required to break down and release nutrients into the soil. Since they need warmth and moisture to do their job, the effectiveness of organic fertilizer is limited seasonally. Organic fertilizers break down according to nature’s rules, so they may not release nutrients as soon as. Nutrient ratios are often unknown.
Although the development and application of microbial bio-fertilizers which are living microbial inoculants that continue to live in close association with crop plants and supply nutrients in synchrony and provide other benefits to them(Kulasooriya, Seneviratne and Ekanayake,unpublished).