Improving Crop Yield and Fertilizer Use Efficiency with One-Time Nutrient Deep Placement.

Major nutrient loss can be high in rice (Oryza sativa L.) fields, particularly rainfed rice, where water flowing from field to field during high rainfall not only reduces the nutrient use efficiencies but also has the potential for environmental degradation. Deep placement of urea briquettes has resulted in higher rice yields and reduced nitrogen (N) losses. We examined the influence of deep-point placement of N, phosphorus (P), and potassium (K) briquettes compared to broadcast incorporation of N, P, and K on rice yield and floodwater nutrient loads. At the same time, fertilizer application was simplified by a single deep-point placement. The studies were conducted at the IFDC greenhouse and on wet season rice in a Vertisol at IGAU. Broadcast application of N as urea resulted in, on average, 10 times higher amounts of ammonium N in floodwater compared to urea deep placement. The broadcast application of single superphosphate resulted in 67 times higher amounts of P in floodwater than plots receiving deep-placed P. The floodwater ammonium-N, P, and K content in the deep-placement treatments was similar to floodwater N, P, and K content without fertilizer application. Significantly higher grain and straw yields, total N, P, and K uptake, and N and P use efficiencies were observed with deep placement. The NPK deep-placement technique is now being compared, in greenhouse and field trials, with fertigation on upland crops such as tomatoes.