Field-based Evaluation of Rice Suitability Classification as Influenced by Cultural Management Interventions

Rice production is constrained by declining soil fertility, imbalanced fertilizer use, climate variability and cultivation in areas with biophysical limitations. Land suitability assessments provide guidance for sustainable production but often lack field validation. This study validates rice land suitability by evaluating agronomic performance, yield and aims to identify site-specific fertilizer responses and recommend interventions to improve productivity across marginal, moderate and highly suitable areas.

Field experiment were conducted in three selected rice farms such as Cahumpan, Calbayog, Samar, Philippines: highly suitable classification, Guinbaoyan Sur, Calbayog, Samar, Philippines: moderately suitable and Rizal, Calbayog, Samar, Philippines: marginally suitable from December 2022 to December 2023 to validate the different level of rice suitability and its specific fertilizer recommended rates. Treatments are: T₁- Farmers’ practice (FP): Traditional red rice transplanted without fertilizer; pre-emergence herbicide applied 10 days before transplanting; no post-transplant weeding. T₂- Good agricultural practice 1 (GAP1): Red rice (local variety) transplanted with basal fertilization (general recommended rates) at 200 kg ha^-1 complete fertilizer (14-14-14) and 50 kg ha^-1 urea (45-0-0). T₃- Good agricultural practice 2 (GAP2): Traditional red rice transplanted with site-specific fertilization based on soil analysis: 100–40-30 kg N-P₂O₅-K₂O ha^-1 for marginal areas, 120–60-100 for moderately suitable areas and 100–20-30 for highly suitable areas. T₄- Good agricultural practice 3 (GAP3): Certified NSIC Rc 216 transplanted with basal fertilization (general recommended rates) at 200 kg ha^-1 complete fertilizer and 50 kg ha^-1 urea. T₅- Good agricultural practice 4 (GAP 4): Certified NSIC Rc 216 transplanted with soil analysis-based fertilization: 100–40-30 kg N-P₂O₅-K₂O ha^-1 (marginal), 120–60-100 (moderate) and 100–20-30 (high).

Rice agronomic and yield performance varied across suitability classifications and GAPs. While the local red rice exhibited taller plant height, NSIC Rc 216 consistently produced superior yield components, particularly in marginally and moderately suitable areas under soil-based fertilizer recommendations (GAP 4). In highly suitable areas, GAP 3 and GAP 4 resulted in comparable performance. Fertilizer application based on soil analysis improved red rice yield, whereas farmers’ practice produced the lowest results. Overall, the adoption of certified inbred varieties, site-specific nutrient management, proper timing of fertilizer application and integration of organic and inorganic fertilizers are recommended to enhance productivity, reduce costs and improve soil health.