Background:
Climate variability significantly constrains agricultural productivity, particularly in rainfed systems where precipitation governs soil moisture and crop growth. In Nigeria, declining and erratic rainfall patterns threaten rice production, a staple crop critical for food security. Precipitation effectiveness, including rainfall timing and distribution, plays a key role in determining yield outcomes and shaping agroecosystem resilience under changing climatic conditions.

Objectives:
This study examines the influence of precipitation effectiveness indices on rice yield in Langtang South, Nigeria, aiming to identify key rainfall determinants of productivity and evaluate their implications for agroecosystem resilience under rainfed agricultural conditions.

Methods:
The study was conducted in Langtang South LGA, Plateau State, Nigeria, a tropical wet–dry climate region. Daily rainfall data (2001–2025) were obtained from the College of Agriculture Garkawa, while rice yield data were sourced from the Plateau State Ministry of Agriculture. Precipitation effectiveness indices (PEI) including hydrologic ratio, dry spells, rainfall onset, cessation, length of rainy season, and number of rainy days were computed. Descriptive statistics were used to summarize temporal patterns. Relationships between PEI variables and rice yield were examined using multiple linear regression, with additional generalized additive models (GAM) applied in R to capture potential non-linear effects and thresholds.

Results:
Results indicated onset dates typically begin in April, fluctuating slightly year to year within a narrow nine-day window. Rainfall onset was consistent across the study period. Cessation generally occurred in late October, though some years exhibited shorter growing seasons and reduced yields, while peak yields were recorded in other years (approximately 4.0 t/ha). Cessation rainfall showed high variability. Overall, intra-seasonal rainfall variability influenced agricultural outcomes more than total annual rainfall. Regression showed an observed trend between precipitation effectiveness indices and yield (R = 0.589), explaining 34.7% variance but not significant (p = 0.122). Relationships were predominantly linear, with no strong evidence of non-linear or threshold effects. Yield variability suggests limited agroecosystem resilience to intra-seasonal rainfall fluctuations. Only rainfall had a significant negative effect on yield (p = 0.048); other variables were not significant. These findings advance understanding of intra-seasonal precipitation dynamics as a primary driver of rice yield variability in tropical rainfed systems, providing a framework for improved agroclimatic management and resilience assessment under variable climate conditions.

Conclusion:
The study identifies intra-seasonal rainfall variability as the dominant driver of rice yield fluctuations in Langtang South. Yield variability reflects limited agroecosystem resilience to rainfall fluctuations, with relationships largely linear and no strong evidence of non-linear or threshold effects.