Balanced Nitrogen, Phosphorus and Potassium Application Enhances Plant Tissue Nutrient Budgets and Grain Yield in Rice

Rice (Oryza sativa L.) production on smallholder farms remains limited due to imbalanced fertiliser use, which hampers nutrient recovery and reduces plant growth and yield. This study aimed to enhance nutrient accumulation, growth, and grain yield in rice through targeted nitrogen (N), phosphorus (P), and potassium (K) fertilisation. A field experiment was conducted in February 2025 at the Lower Moshi Irrigation Scheme in Tanzania using fourteen NPK treatments and the variety TXD 306. Baseline soil fertility was assessed from samples collected at 0–30 cm depth, and plant growth, nutrient uptake, and yield data were recorded at booting and maturity. Results showed that fertilisation significantly (p < 0.05) influenced nutrient concentrations, uptake, and yield. At booting, the treatment with 300 kg N ha-1 + 20 kg P ha-1 + 25 kg K ha-1 produced the highest leaf N concentration (10.9%) and N uptake (370.3 kg ha-1), while P and K uptake peaked at 13.8 kg ha-1 and 20 kg ha-1, respectively. At maturity, N, P, and K uptake increased to 555.6, 26.1, and 97.6 kg ha-1, respectively. The same NPK combination produced the highest grain yield (6.5 t ha-1) with 171 spikelets per panicle. Excessive N (360 kg ha-1) lowered grain yield to 1.4 t ha-1 despite vigorous vegetative growth. Results indicate that balanced N, P, and K application enhances nutrient uptake and grain yield, while overusing nitrogen hampers production. Optimised nutrient management provides a practical approach to boost rice productivity in similar agroecological settings