Agriculture, the backbone of human civilization, is increasingly facing challenges due to soil degradation, nutrient depletion, and environmental concerns arising from the misuse of chemical fertilizers. To address these issues, a sustainable and environmentally conscious approach is imperative. One promising avenue is the utilization of industrial by-products and wastes as plant nutrients. This book explores the potential of these materials to enhance soil fertility, reduce waste, and foster sustainable agricultural practices. Modern agriculture heavily depends on chemical fertilizers to meet the nutritional demands of crops. While effective in boosting yields, their excessive and prolonged use has led to detrimental environmental consequences, such as soil acidification, water pollution, and greenhouse gas emissions. Moreover, the limited availability of raw materials used in fertilizer production, such as phosphorus rock, highlights the urgency of finding alternative nutrient sources. Concurrently, industrial processes generate substantial quantities of organic and inorganic by-products, many of which are either underutilized or disposed of as waste, posing environmental hazards. Using these by-products as plant nutritional sources brings together waste management and sustainable agriculture. Industrial by-products can replenish essential nutrients, reducing the dependency on synthetic fertilizers. Organic by-products enhance soil organic matter, improving water retention, aeration, and microbial activity. Inorganic by-products, on the other hand, provide a steady release of nutrients, ensuring sustained plant growth. Diverting industrial wastes from landfills or incineration to agricultural fields mitigates environmental pollution. This practice aligns with circular economy principles, promoting resource efficiency Utilizing industrial by-products can significantly reduce input costs for farmers, especially in regions where access to commercial fertilizers is limited. Industries also benefit by reducing disposal costs and compliance burdens. Recycling wastes into agriculture reduces greenhouse gas emissions associated with waste disposal and fertilizer production. It also mitigates leaching and runoff, protecting water bodies from eutrophication. Despite its potential, the use of industrial by-products in agriculture faces several challenges. Many industrial wastes contain heavy metals, pathogens, or toxic compounds that pose risks to soil health, crop safety, and human health. To ensure these materials are used safely, rigorous treatment processes and strict quality standards are essential. This requires implementing strong regulatory frameworks and conducting thorough risk assessments. Technologies such as bio-remediation and thermal treatment can detoxify hazardous components in the industrial by-products. Farmers and consumers may be sceptical about using “waste” as a nutrient source due to concerns over safety and effectiveness. The collection, processing, and distribution of industrial by-products require infrastructure that may not exist in all regions. As the world’s human and animal population continue to grow, the demand for food and food production will rise, leading to increased waste generation and environmental challenges. In addition, more than two billion people worldwide are at risk of developing a micronutrient deficiency due to a lack of essential nutrients in their daily diet. The primary cause of this nutrient deficiency is that food crops often fail to supply adequate nutrients because they are grown in mineral-deficient soils. In most developing countries, agricultural production focuses primarily on increasing crop productivity and grain yield, often overlooking the challenges of malnutrition. Environmental, human, animal, and climate health, as well as sustainable agricultural production and agro-industrial processing, heavily rely on efficient waste management. To achieve the goal of significantly reducing waste creation, reusing waste, and recycling trash, circular agricultural production and bio-economic agro-industrial waste management models are essential. The goal of transforming waste into valuable resources and establishing a zero-waste agricultural production system can be achieved through ongoing research and innovative thinking. This textbook covers the classification of elements and their effects on plants, emphasising the physiological, biochemical, and antioxidant characteristics of plants. It also highlights the possible use of industrial and agricultural wastes and by-products in agricultural production, including case studies as well. This approach not only recycles nutrients, improves soil health, and reduces environmental pollution, but also supports global efforts to achieve sustainable development goals. However, its successful implementation will require collaboration among industries, policymakers, researchers, and farmers. If supported and successfully implemented, industrial by-products can transform from being an environmental liability to a valuable agricultural asset, paving the way for a greener and more resilient future.