Achieving profitable rice crop through balanced fertilizer mix – the case of Southwestern Madagascar

In Madagascar, the most important staple crop rice is being cultivated mainly using locally available organic inputs. The current rice yields are at 2 t/ha and inorganic fertilizers are vital for enhancing rice productivity. However, the recent rapid increase in fertilizer prices, aggravated by the Russia-Ukraine crisis, combined with low farmgate paddy prices, has made use of inorganic fertilizers unprofitable for farmers. When farmers apply inorganic fertilizer like ‘Urea’, the yield increases but overall profit goes down compared to ‘growing rice without inorganic fertilizers’. This is purely because of high fertilizer prices and low paddy prices. Inorganic fertilize price was tripled in Madagascar. 5 years ago, Urea was USD 0.5 /kg while today it costs USD 1.5/kg. Consequently, farmers have to rely solely on locally available organic inputs, abandoning the use of inorganic fertilizers.

But how effective are these organic alternatives, and can a combination of both inorganic and organic inputs be the key to profitability and higher yield?

A study was conducted in the southwestern region of Madagascar, where rice can be grown for two consecutive seasons in a year, to determine the best combination and rate of inorganic fertilizers and organic inputs for maximizing yield and profitability. Nitrogen (N) was identified as the most limiting nutrient for rice production in this region, so the study was focused on different fertilizer treatments involving three levels of nitrogen (30 kg/ha, 60 kg/ha, and 90 kg/ha). These treatments included using either inorganic or organic fertilizers, as well as a combination of both, with a control (no fertilizer applied) for comparison.

Using suitable rice variety (Sebota70) for the region, we found that the dry season yields were higher (4.5 t/ha) compared to the wet season (3.8 t/ha). All fertilizer treatments showed significantly higher yields compared to the control. Inorganic fertilizers performed better than the combination of inorganic and organic inputs, while organic inputs had the lowest yield among the three sources at the same N rate, irrespective of the N input levels.

Figure 1: Comparison of grain yield (A), incremental benefit:cost ratio (B) per treatment for both wet and dry season, in southwestern of Madagascar. The incremental benefit-to-cost ratio evaluate the increased benefit attributable to the fertilizer treatment compared to a control, with the incremental costs (cost of the fertilizer, application costs) associated with using the treatment.

Control – No application of fertilizer

M1 – application of mineral fertilizer only at low N level (30 kg/ha)

M2 – application of mineral fertilizer only at medium N level (60 kg/ha)

M3 – application of mineral fertilizer only at high N level (90 kg/ha)

MO1 – combination of mineral and organic fertilizer at low N level (30 kg/ha)

MO2 – combination of mineral and organic fertilizer at medium N level (60 kg/ha)

MO3 – combination of mineral and organic fertilizer at high N level (90 kg/ha)

O1 – application of organic input only at low N level (30 kg/ha)

O2 – application of organic input only at medium N level (60 kg/ha)

O3 – application of organic input only at high N level (90 kg/ha)

Although the inorganic fertilizers produced higher yields, the profitability did not correspond proportionally due to the current higher inorganic fertilizer price (e.g., Urea at USD 1.5/kg) and lower farmgate paddy price (USD 0.22/kg). During the wet season, none of the fertilizer treatments provided significantly higher net profit than the control. In the dry season, medium (60 kg N/ha) and higher (90 kg N/ha) N levels with inorganic fertilizers and a combination of organic + inorganic inputs produced higher net profit. However, the higher incremental benefit-cost ratio for fertilizer application was observed at lower N levels for the combination of inorganic + organic inputs, and organic inputs alone. Increasing N levels using inorganic or combined inorganic and organic inputs led to higher yields in both seasons. However, relying solely on organic inputs at higher N levels did not result in a similar yield increase.

This study emphasizes the importance of finding the right balance in fertilizer combinations for smallholder rice farmers in Madagascar and the larger sub-Saharan Africa. Understanding the relationship between yield, profitability, and different fertilizer sources can help researchers and policymakers develop strategies to support farmers and improve food security. In the case of Madagascar, for farmers to maximize their profitability, they can skip applying fertilizers for the wet season rice. However, for the dry season rice, to achieve higher profitability, it is advisable to apply the combination of both organic and inorganic fertilizers or only organic inputs at a low N rate of 30 kg/ha.