<p>The increasing demand for sustainable agricultural practices has led to the exploration of biopolymers as eco-friendly alternatives for enhancing crop productivity while reducing environmental impact. This review investigates the structural and functional properties of biopolymer-based materials in precision agriculture and composite fertilizers. Biopolymers such as chitosan, sodium alginate, and starch exhibit remarkable potential due to their biodegradability, biocompatibility, and ability to control nutrient delivery. Chitosan-based biosensors facilitate early detection of plant diseases and nutrient monitoring, while hydrogel-based soil moisture sensors enable optimized water management. Sodium alginate aerogel beads and starch-derived hydrogels in composite fertilizers enhance nutrient use efficiency, soil structure, and water retention, offering a controlled release mechanism to minimize nutrient loss. This paper also highlights advancements in nano-based biosensors for real-time detection of agrochemical contaminants and their role in precision farming. In addition, the review critically analyses the comparative effectiveness of biopolymer-based inputs versus conventional inputs, outlines their advantages and limitations, and discusses key economic, technical, and regulatory challenges. Future research directions emphasize the need for scalable biopolymer production, integration of smart technologies, and development of multi-functional biopolymer composites for sustainable agriculture. By addressing these aspects, this review provides a comprehensive perspective on the transformative role of biopolymers in achieving eco-efficient agricultural systems and tackling global challenges such as resource scarcity, environmental degradation, and food security.</p>