The correct option is 1, 3, and 4 only because fertigation, which combines fertilization with irrigation, allows for precise control over nutrient delivery, thereby enhancing the availability of nutrients to plants (3) and reducing nutrient leaching (4). It also aids in managing the alkalinity of irrigation water (1), ensuring that the right pH levels are maintained for optimal nutrient uptake. However, the statement regarding the efficient application of Rock Phosphate (2) is misleading, as Rock Phosphate is less soluble and not typically suitable for fertigation compared to other fertilizers that are more water-soluble.

This understanding is pivotal in UPSC exams as it ties into broader themes of sustainable agricultural practices, water management, and soil health, reflecting a holistic approach to optimizing resource use in farming.