Phosphorus application affects lowland rice yields by changing phenological development and cold stress degrees in the central highlands of Madagascar

Abstract

Despite a general perception that phosphorus (P) deficiency delays phenological development in annual crops, the impacts of interaction between this phenological delay and climatic conditions on crop productivity remain poorly understood. On-farm experiments were conducted in the central highlands of Madagascar, where P deficiency and late-season low temperature stress frequently restrict rice yields. Rice X265 was grown under four different fertilizer treatments with different combinations of N and P during early, intermediate, and late transplanting dates (ETP, ITP, and LTP, respectively). Plants subject to no fertilizer or single N treatments showed delayed heading by 6–24 days. This notable delay in the phenological development favored biomass accumulation and resulted in greater yield in ETP when low temperature stress was negligible. In contrast, delay in phenological development without P application increased cooling degree days and spikelet sterility in ITP. Consequently, the effect of a single N application had a positive effect only in ETP. The effect of P was much greater in ITP than in ETP because P application alleviated not only P deficiency but low temperature stress as well by shortening day to heading. In LTP plots, yield was severely suppressed to less than 1 t ha−1, with sterility rate above 75 %, irrespective of fertilizer treatment. This study provides field evidence that phenological delay under P deficiency has dual effects on grain yield and that optimal N and P management practice differs with climatic growing conditions. Changes in phenological development due to plant nutrient status and its interaction with climate-induced stress needs further attention for improving fertilizer management practice.

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