Management of Alternative Organic Fertilizer Sources for Wheat Production: Evidence from Decomposition Dynamics and Agronomic, Economic, and Farmers’ Preferences

Abstract

The increasing cost of mineral fertilizer has posed a barrier for smallholder farmers, resulting in lower application rates, declined soil fertility status, and crop yield. Therefore, it is vital to look for cheap, impactful, and locally accessible organic fertilizer sources. Thus, two-year on-farm studies were conducted to evaluate potential organic fertilizer sources based on their decomposition dynamics and agronomic, economic, and farmer preference responses. The organic fertilizer sources used were dried tree leaves of Croton macrostachyus (Cm) and Erythrina bruci (Eb) and farm yard manure (FYM) and their mixture at ratios of 1 : 1:0, 2 : 1:0, and 1 : 1:1 Cm : Eb : FYM, respectively. The organic materials were buried using litter bags at 5 tons ha−1 rate in the crop field and retrieved at the weeks of two (14 days), four (28 days), six (42 days), and eight (56 days) after placement. Data were collected that included dry mass (DM) remaining, daily decomposition rate (k), and half-life (t1/2). Furthermore, to validate the findings of litter bag trials, the mixture of three organic fertilizer sources [1 : 1 : 0, 2 : 1 : 0, and 1 : 1 : 1 of Cm : Eb : FYM] and four application times (two, four, six, and eight weeks before sowing) were evaluated on bread wheat (Triticum aestivum) as a test crop in factorial randomized complete block design in a factorial arrangement with three replications. Data on agronomic, economic, and farmers’ preferences were recorded. The result revealed an increased weight loss over 56 days in the order of 2 : 1 : 0 > 1 : 1 : 0 > 1 : 1 : 1. The k value significantly ($P<0.05$) varied among organic fertilizer sources. The k value (% day−1) in 2013 varied between 3.42% and 0.023%, whereas in 2014, it was 3.10% and 0.23% for Cm and FYM, respectively. The k value was in the order of Cm > 2 : 1 : 0 > 1 : 1 : 0 > Eb > 1 : 1 : 1 > FYM. Applying organic fertilizers two weeks before sowing significantly improved wheat performance compared to applications made eight weeks prior. For example, the mean grain yield was 4.1 tons ha−1 and 2.6 tons·ha−1 at two and eight weeks before sowing, respectively. Although there were no statistically significant differences among the mixed sources, the 2 : 1 and 1 : 1 over 1 : 1 : 1 proportion have resulted in a higher grain yield. Farmers showed the highest preference rank for 2 Cm : 1 Eb and 1 Cm : 1 Eb, incorporated two weeks before sowing. The partial budget analysis demonstrated the highest net benefit from applying two weeks before sowing and 2 Cm : 1 Eb organic material mixture. Considering the findings generated from the decomposition test, agronomic and economic evaluations, and farmers’ preferences, we could conclude that the wheat growers should use 2 Cm : 1 Eb and incorporate it into the soil two weeks before sowing.