STA. MARCELA, Apayao – The Department of Agriculture in the Cordillera (DA-CAR) has started testing various fertilizers in the rice plantations of Sta. Marcela and Luna, Apayao to determine the most suitable fertilizers to use in the said planting areas.
DA-CAR Research Division Senior Science Research Specialist Esther Andiso explained the measure seeks to assist farmers on what specific fertilizers would be appropriate for a particular farming area through the Nutrient Omission Plot Technique or NOPT.
“These planting areas in Apayao are the first areas where we are conducting the Nutrient Omission Plot Technique to estimate the fertilizer requirement of a particular planting area. With these tests, we are able to assess what appropriate fertilizers our farmers can use that would give them a higher yield in terms of rice production,” Andiso said.
In an omission plot, adequate amounts of all nutrients are applied except for the nutrient of interest (the omitted nutrient). The yield in such an omission plot is related to the indigenous soil supplying capacity for the omitted nutrient. For example, if all nutrients except for Potassium (K) are applied in a K omission plot, the yield will be limited by the indigenous supply of K (that is K derived from soil, residue, organic materials, irrigation water, and sediments).
The yield gap between a target yield and the yield in the omission plot is then used to calculate fertilizer requirements. Omission plots make any nutrient limitations visible.
Separate omission plots are needed for each nutrient. It is better to get a good yield average for each nutrient from several omission plots placed in a larger area than to use a single plot in one farmer’s field.
“Through NOPT, we can determine not only the specific fertilizer to be used in a farming area but the amount to be used and how many times a fertilizer is to be applied. It can also forecast the yield it may produce provided the farmer follows the necessary computations done by our agricultural technicians.” Andiso added.
Omission plots are often used for major nutrients such as Nitrogen, Phosphorus (P), and Potassium (K) and should be installed in high-yielding seasons in farmers’ fields. Use good-quality seeds and follow proper crop management, including water and pest control.
Select 10−20 representative farmers’ fields for a larger area with similar soil conditions, and establish a 20 x 5 m plot in each farmer’s field. Divide the plot into four 5 x 5 m omission plots. Bunds between plots should be 25 cm wide and 25 cm high to limit nutrient movement between plots.
The limitation of the technique is a needed community or extension effort to calculate fertilizer requirements, aside from estimating indigenous nutrient supply using grain yield in omission plots that may be affected by crop management, adverse weather, and/or pest damage.