Assessment of the combined effects of organic manure and NPK (17-17-17) on growth and yield of carrots in Rwanda

Carrot (Daucus carota L.) is one of the most important vegetable crops grown in many parts of Rwanda. However, its yield and growth are still low among many smallholder farmers partly due to limited knowledge on proper fertilizer use and application. To address this issue, the study was conducted to assess the effect of combined application of organic manure with different rates of NPK (17-17-17) on growth and yield of carrots in Rwanda. Understanding the impact of organic manure and NPK fertilizers on carrot growth and yield can help farmers optimize production, and enhance food security and economic development in the region. A field experiment was undertaken in season 2022-2023 in three agro-ecological zones (AEZs) in three different provinces of Rwanda namely, Huye (Southern province), Bugesera (Eastern) and Rubavu (Western) districts. Eight treatments were arranged in a randomized complete block design (CRBD) with three replications. Each of the eight treatments received a uniform application of 25 tons per hectare of organic manure. Additionally, inorganic fertilizers (specifically NPK 17-17-17) were introduced in varying quantities, except for the control plot(T0), which did not receive any NPK. The treatments (T) were arranged as follows: T0 (Control) = 0 kg/ha, T1= 50kg/ha, T2= 100 kg/ha, T3=150 kg/ha, T4=200 kg/ha, T5=250 kg/ha, T6=300 kg/ha and T7= 350 kg/ha. Data collected from the experiment were subjected to analysis of variance (ANOVA) using R Studio. The analysis aimed to evaluate the impact of the different treatments on the growth and yield of carrots in the three agroecological zones (AEZs) represented by the Huye, Bugesera, and Rubavu districts. Results showed variations in carrot growth and yield based on fertilizer rates across all AEZs. Among the treatments, Treatment T7, receiving 350 kg/ha of NPK, exhibited a significant increase in the number of leaves and plant height compared to other treatments. Conversely, the control plots (T0) exhibited the lowest plant height and number of leaves across all AEZs. Similarly, the T7 also resulted in the highest carrot yield of 7.1 kg, outperforming all other treatments. In contrast, the control group (T0) exhibited the lowest yield of 3.3 kg. These findings suggest that combining 25 t/ha of organic manure with 350 kg/ha of NPK can significantly boost carrot production in various regions of Rwanda. The use of organic manure combined with NPK fertilizers can provide essential nutrients to the carrots, promoting their growth and yield. This information can be valuable for carrot farmers in the three AEZs of Rwanda, as it offers a practical approach to improving carrot production and increasing yields. Key words: Carrot, agro-ecological zone, fertilizer, growth and yield, Rwanda