Production of sweet corn generates massive agricultural wastes, particularly corncobs, which are usually incinerated, resulting in environmental and health issues. Converting wastes into biochar through slow pyrolysis offers an environmentally friendly option. Biochar is a carbon-rich by-product that improves soil properties such as pH, nutrient status, water retention, and microbial activity. Farmyard manure (FYM), a traditional soil conditioner, also improves soil fertility through the introduction of organic matter and nutrients. Current studies show that the mixing of biochar with FYM has complementary impacts, significantly improving soil structure, nutrient absorption, and yield of crop. This combined strategy enhances sweet corn cultivation through sustainable farming, reduction of environmental stress, and soil sustainability. Application of FYM in combination with sweet corn waste for the production of biochar is a viable method of efficient waste management and climate-resilient agriculture.

Pyrolysis, cob biochar, pervious, farmyard manure, fertilizers, sustainable agriculture.

Sweet corn (Zea mays L. saccharata) or the sugar corn is gaining popularity, as the cob is tender and flavor, is accepted for straight consumption. Sweet corn cultivation is found highly rewarding and can be cultivated throughout the year with successful yield. Sweet corn is quickly becoming popular among all the segments of population because it is highly nutritive and rich in protein and fibre (Lal et al., 2018). Its use at young stage as boiled and roasted ears is a common practice since the kernels are sweet, tender, creamy, and crunchy and checks nearly shell-less. Owing to its additional sweetness of taste and softness, sweet corn growing is the priority of the farmers particularly in agriculture. After corn stalks and leaves are harvested, a vast amount of agricultural waste is left behind. Corn cob is a byproduct that remains after all the kernels have been removed. Mostly farmers use burning as a means of getting rid of this farm waste. But this is not good as it leads to local air pollution issues, soil degradation, and impacting human health. To prevent the burning of biomass, it is vital to determine how this waste can be used. This issue can be addressed in agriculture by using slow pyrolysis to produce biochar from the corncob trash (Gabhane et al., 2020). Biochar is a fine grained, carbon dense, pervious residue left after plant biomass has undergone thermo-chemical conversion process (pyrolysis) under conditions of little or no oxygen (Devika et al., 2018). Physico-chemical properties like bioavailability of nutrients, cation exchange capacity, pH, strength of soil, and water holding capacity can be altered in the soil with the biochar application (Khan et al., 2024). Biochar enhances crop root development and nutrient uptake by ameliorating soil structure, moisture retention, and nutrient availability (Hussain et al., 2017). Even though biochar has a lot of potential, it's essential to remember that FYM is a classic agrarian practice. Because of its high organic matter content, FYM ameliorates soil structure, provides nutrients, and encourages favorable microbial activity (Balda and Giri 2023). A steady supply of nourishment to plants occurs when the gradual release of nutrients takes place with the breakdown of organic matter. The benefit of FYM and biochar is they work together to create a synergistic interaction. Results from applying these modifications together are greater than those being applied alone (Arif et al., 2012). Biochar has also proven to enhance the soil microbial activity. FYM promotes microbial diversity, enriches organic matter, and is a great nutritional supplementation in the short term. Hence, the combined use of biochar and FYM may represent a holistic strategy that maximizes the soil fertility, improves climate resilience and eventually promotes sustainable agriculture practices in sweet corn.

Properties and Benefits of FYM: FYM is a heterogeneous product of animal excreta and bedding materials like urine soaked litter developed by anaerobic decomposition. Organic matter, microbial biomass, moisture level (50%-70%) and inorganic mineral components are the main constituents of FYM. The supplement material of FYM varies with the support of animals, type of animals, harvesting techniques and capacity levels. Properly composted FYM provides easily available nutrients N, P, and K along with necessary supplements (Bayu et al., 2006). FYM also serves as a source of organic carbon when it breakdown in the soil.

Fig. 1. Farmyard manure.

Hydraulic conductivity was enhanced to a great extent, and bulk density was reduced by applying farmyard manure under deep tillage (Khan et al., 2010). Desta (2015) performed a field experiment at the Antra catchment of Chilga to investigate the effect of natural and chemical fertilizers on soil properties under maize and identified that the integrated application of natural and inorganic fertilizers improved soil pH, organic carbon, and cation exchange capacity when compared to the control. The advantageous impact of FYM on yield-contributing characters was the main reason behind increased grain yield at the enhanced level of FYM. FYM provides all macro and micro nutrients required for plant growth and also activates microbial population and physical condition of soil, thereby affecting yield-contributing characters (Bhat et al., 2013). The impact of integrated application of natural and chemical fertilizers on soil microbes reported that natural fertilizers had a significant effect on microbial and parasitic populations, where microbial (8.24 log cfu g⁻¹ soil) and fungi (3.89 log cfu g⁻¹ soil) richness was greater under integrated application of fertilizers (Kumar et al., 2017). The most feasible technique for enhancing the count of actinomycetes and bacteria was to use FYM with NPK fertilizer (Jagathjothi et al., 2008). Sustainable improvement in soil's physical environment, carbon sequestration, raised productivity, and efficient use of water and nutrients can be achieved by implementing integrated application of inorganic fertilizers at optimum levels and farmyard manure in every wheat crop season (Meena et al., 2018).

Cob Biochar Production: A carbon-rich residue of heating biomass in a confined area with little oxygen is called biochar (Panwar et al., 2019). Pyrolysis is a low-cost and straightforward process that has been employed to make biochar. The most pivotal factor in pyrolysis is temperature because all of the basic physical changes depend on it. Low temperatures and extended residence times are preferred for the solid biochar product, while higher temperatures and shorter residence times are preferred for the liquid biochar product (Shariff et al., 2016). After being gathered from the field, the feedstocks should be sun-dried for two days until all of the humidity has faded (Anika et al., 2022). To lower the humidity content to a safe level for processing and storage, the cobs are needed to be dried. Drying can be accomplished naturally with the sun or air, or with mechanical dryers. Maize cob farm waste was pyrolysed in a resistance box muffle furnace for the purpose of getting a biochar at various temperatures (300-500 C) (Adekanye et al., 2022). When temperatures rise, the quantum of biochar produced diminishes because of either the primary breakdown of feedstocks or the secondary breakdown of biochar residues (Shariff et al., 2016). The resulting biochar was successfully characterizeised by varying the physico-chemical and structural characteristics of the biochar (Adekanye et al., 2022). A slower rate of heating has proven to yield better results when compared to faster rate of heating (Bartoli et al., 2022). Compared to other temperatures, maize cob biochar generated at 600 C has a higher fixed carbon concentration (Shariff et al., 2016). A yield of roughly 34% was attained by slow pyrolysis of corncobs at 500 C for 60 minutes of residence time and pyrolysis temperature (Rattanaphaiboon et al., 2022). The biochar was crushed to a fine powder and sieved following the pyrolysis process (Rekaby et al., 2021).

Fig. 2. Corn cob and Corn cob biochar.

Physico-Chemical Properties of Cob Biochar: Corncobs, which are exclusively utilized as agrarian waste, can be converted into biochar; a more valued functional product. The biochar can enhance the C, N, Ca, Mg, K, and P availability to plants because the biochar is a reservoir of nutrients having a long-term effect on microbial development upon release in the soil solution. The quantum of potassium (K) and silicon (Si) in biochar influences its thermal stability (Anika et al., 2022). When the pyrolysis temperature increased, the biochar's carbon content increased from 45.5% to 64.5%, but the oxygen content dropped at the same time which indicates carbonization was enhanced with rising pyrolysis temperature (Rafiq et al., 2016). Studies indicate that a higher temperature could affect in a larger fixed carbon product for the maize cob (Adekanye et al., 2022). Biochar can be used to manage nitrogen losses because it increases cation exchange capacity (Liang et al., 2006), decreases nitrous oxide emissions, and retains nitrogen (Chan et al., 2008). Corncob-derived biochar has a pH of 8.59 due to pyrolysis's impact on the organic material's separation from alkaline salt (Rattanaphaiboon et al., 2022). Although the temperature is raised from 300 C to 500 C, the porous structure of the biochar made from maize cobs can expand because of thermal cracking brought on by the release of volatile matter, the biochar is not porous at 300 C (Adekanye et al., 2022). After pyrolysis, corncob biochar showed more porosity, with internal holes that were usually between 0.5 and 3 μm (Rattanaphaiboon et al., 2022). The unstable matter and dampness substance of the corncob biochar were decreased to 1.78% and 33.05%, individually, and the fiery remains and settled carbon were raised to 59% and 6.13%, separately (Rattanaphaiboon et al., 2022). Elimination of phenol in aqueous solution was done by using modified biochar, which was created by chemically activating biochar made from corncob pyrolysis (Wang et al., 2020). Biochar surface area of maize cob grew with pyrolysis temperature to 199 m²/g at 300  C, 231 m²/g at 400  C, and 291.8 m²/g at 500 C, with maximum surface area recorded at 500  C owing to the temperature factor (Adekanye et al., 2022). By improving the physico-chemical and biological properties of soil, corn cob biochar can promote nutrient uptake, healthy plant roots, and plant growth. An rise in the efficiency of dry matter, carotenoid, chlorophyll, and nutrient consumption demonstrates that the cob biochar has significantly improved the condition of soil (Rekaby et al., 2021). Corn cobs can be converted into biochar to improve the characteristics of highland acidic soil, promote soil adaptation, and decrease carbon loss from agrarian waste (Nurida et al., 2023). Besides being a good absorber of nutrients and agrarian chemicals, corn cob biochar has the implicit to be a significant soil supplement since it retains the maturity of the mineral nutrients set up in corn remainder and may store carbon.

Table 1: Difference between Farmyard manure and Corn cob biochar.

Synergistic Effects of FYM and Cob Biochar on Sweet corn Productivity: The increase in biological yield of maize through the combined use of farmyard manure, biochar, and nitrogen fertilizer can be attributed to soil fertility advancements, higher nutrient contents, and larger carbon stores, promoting to crop growth, productivity (Agegnehu et al., 2017) and quality parameters. Cumulatively, organic amendment and biochar application would delay the silking tasseling and increases grain protein and oil content (Ali et al., 2017). Soil carbon after maize harvest was significantly higher when 50 t BC was combined with 10 t FYM per hectare compared to just 5 t FYM (Ali et al., 2018). Organic amendments like FYM and biochar enhances grain yield in addition to enhancing the structure of soil, water holding capacity, and nutrient supply (Singh et al., 2022). Biochar when applied along with nitrogenous fertilizer promotes the nutrient uptake by plant which leads to an increase in yield attributes and yield (Naeem et al., 2018). Biochar enhances the flow of water and nutrients through the soil, improves carbon content and microbial population and improves the maize grain yield because of its pervious nature and immense surface area (Ali et al., 2021). Higher yield occurs in maize due to improved nutrient uptake, root development, and effective distribution of carbohydrates from leaves to reproductive parts (Nagaveni et al., 2024). Farmyard manure, biochar, and nitrogenous fertilizers in combination plays a significant role in augmenting the condition for maize growth by increasing soil organic matter and cation exchange capacity, conserving nutrients, and provides good environment for microbial growth (Arif et al., 2012). It also improves the microbial activity and nutrient utilization efficiency in soil (Song et al., 2019). Application of biochar along with fertilizer can increase crop yield far beyond employing biochar to treat the soil (Ali et al., 2018). Regulation of nutrients and boosting soil retention and nitrogen use in maize farming were found with the application of N fertilizers with the appropriate type of biochar (Li et al., 2023).Yield and yield components of corn can be increased with conglomerate application of biochar, FYM and inorganic fertilizers (Arif et al., 2012).

The combined application of FYM and cob biochar has an immense effect on the yield of sweet corn. It promotes sustainable agriculture. Future research should focus on improving crop production and soil fertility as well as discovering the correct combinations of FYM, cob biochar, and inorganic fertilizers that work well under different agro-climatic conditions. It is necessary to make cost-benefit and economically feasible combinations of FYM and biochar so that small farmers can adopt them. Studies should need to be carried out in assessing the impact of FYM, cob biochar, and their combinations on carbon sequestration, nutrient availability, and microbial population in the soil.

Uppada Thanuja  and Kuna Chinna Rao  (2025). A Review: Synergistic Effects of FYM and Cob Biochar on the Growth and Yield of Sweet Corn (Zea mays L. saccharata). Biological Forum, 17(5): 63-67.