Crop residue management becomes the challenging issue to farmers for balancing between the economic and sustainable environment. Though burning is the easiest way of destroying the crop waste it not only causes drastic changes in green house gas but also large amount of nutrients are removed from soil by plants. Hence the technique which protects the environment along with enhancing soil quality is needed. Therefore pyrolysis of crop residue can become an alternate technique against past strategies. The heterogeneous characteristics of the biochar can be produced through the pyrolysis process and that would be employed as a soil amendment. The biochar application ameliorates the problems which persist in soil and enhance the crop production in environmentally sound way. And largely involved in the carbon sequestration thereby sustain the soil quality. However there is lack of information available on effects of long term application of biochar and durability of persistence in soil. Thus in those things made to review on brief account of biochar such as, biochar production, characteristics, impacts on soil properties, crop growth, reduction of green house gases and heavy metal remediation. Moreover, in this review discusses about what are all the challenges and future trust in the application of biochar. So, the deep understanding on biochar and its interaction with soil can bridge the gap prevailed in the scientific field and crop improvement.

Background: In the era of precision agriculture, application of fertilizer based on soil testing is an essential tool to prescribe nutrient doses for crops to improve nutrient use efficiency and yield of hybrid castor. Methods: Field experiment was conducted in 2021 at the Tapioca and Castor Research station, Yethapur, region near Salem city, Tamil Nadu, India (11035’N, 78029’E). By adopting inductive cum targeted yield model fertilizer prescription equation (FPEs) were developed for hybrid castor under irrigated condition for Alfisol soil order. Initially soil fertility gradient were established with respect to soil available N, P and K nutrients and twenty four treatment were imposed in three fertility strips under factorial randomized design. The basic parameters [nutrient requirement (NR) and nutrients contributions from soil (Cs), fertilizer (Cf) and farmyard manure (Co)] were calculated from the field experimental data. Result: The nutrient required for producing one quintal of hybrid castor seed yield was evaluated as 3.20 kg of nitrogen, 1.23 kg of phosphorus pentoxide (P2O5) and 3.28 kg of potassium oxide (K2O). The study revealed that soil nutrient contribution was high in case of available phosphorus (41.87%), available nitrogen (21.56%) and available potassium (19.12%) respectively toward P, N and K nutrient uptake by hybrid castor. The nutrient contribution from farmyard manure (Co) towards the total uptake was 21.40% of N, 10.35% of P2O5 and 26.06% of K2O respectively. Using basic data, FPEs were developed for hybrid castor and ready reckoner were developed for operational range of soil test values for desired yield target under NPK alone and IPNS (NPK and FYM).

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In the era of precision agriculture, the fertilizer prescription based on the soil fertility status is much required.  Analyzing the soil after each crop is necessary for fertilizer recommendation and developing an alternative technique to forecast the soil available nutrient value rather than analyzing the soil. Multiple linear regression (MLR) equation was developed using filed experiment data to predict the soil available nutrient in castor cropping sequence. The post-harvest soil available nutrient was considered as the dependent variable and the initially available soil nutrient values, fertilizer added, yield and nutrient uptake of castor as an independent variable. In general, the post-harvest soil nutrient model's prediction accuracy was notable and had a coefficient of determination of less than 0.90. By calculating the RMSE (root means square error), R2 value, the ratio performance to deviation (RPD) and, RE (relative error) the performance of the MLR model was confirmed.Using the validated model, post-harvest soil available nutrients were predicted and compared with laboratory tested soil available nutreints. It turned out that the established model is more precisely effective and equally precise. Fertilizer recommendation could be made to subsequent crop after hybrid castor using the predicted soil available nutrients.