Concept:When crops are grown in rows, fertilizer should be placed close to the rows so that the roots of each plant can access it easily.
Explanation:Drilling applies fertilizer in continuous bands or furrows along the planted rows. This method is direct, economical, and convenient because the fertilizer is neither wasted between rows nor spread over unplanted ground.
Broadcasting is unsuitable after planting because it scatters fertilizer uniformly over the whole field, much of it falling away from the crop rows. Foliar application is used when nutrients are sprayed onto leaves, while ring placement places fertilizer around the base of individual plants, making it tedious for row-grown field crops.
Therefore, among the given options, drilling is the correct and most convenient method for applying fertilizer to crops already established in rows.
Answer:C. drilling