Yields and Yield Gaps in Lowland Rice Systems and Options to Improve Smallholder Production

Abstract

Increasing productivity per unit area, hence closing the yield gap, is key to meeting cereal demand in sub-Saharan Africa. We assessed, with 114 farmers, the contribution of recommended agronomic practices (RAP) with or without NPK fertilization on yield gaps, and options to intensify productivity. Treatments included farmers’ practice (FP) as control, RAP with and without NPK, and farmer-selected best practices geared towards intensification (farmers’ intensification practice, FIP). RAP without fertilization and FIP significantly increased grain yield, each by ca. 12%, whereas RAP+NPK application produced ca. 33% extra yield, over FP. RAP gave the highest mean net income (ca. USD 220 ha−1), fertilizer costs made RAP+NPK gave the lowest mean net income (ca. USD 50 ha−1). Weeding and fertilization timing contributed most to yield variation among fields. Delay in weeding and fertilization created an average yield loss of 5.3 and 1.9 g m−2, per day delay, respectively. Exploitable yield gap averaged 24 and 29%, respectively, across treatments and under FP. RAP, FIP, and RAP+NPK reduced the exploitable yield gap to 25, 26, and 12%, respectively. We conclude that different yield gap levels can be exploited by smallholder farmers in lowland rice systems as RAP, FIP, and RAP+NPK allow yield gap reduction, although fertilization poses a risk to profit at current rice and fertilizer prices. To realize yield gains, farmers with good water management should combine timely weeding with other crop management practices.

Management practices and rice grain yield of farmers after participation in a joint experimentation

“…Even though lower-yielding farmers made larger yield gains, the overall yields recorded by farmers are still low, for the rice variety grown, when compared with yields observed under researcher-managed on-farm trials in the same study area (Awio et al, 2021). Grain yields recorded in this study are, however, higher than yields earlier reported under farmers' practice in the study area (Senthilkumar et al, 2020;Awio et al, 2022). The lack of yield gain by the top-yielding farmers might imply that at their current management level these farmers could not further raise their grain yields beyond the level observed during joint experimentation, probably because the observed current N input could be too low (which was up to a maximum of 68 kg N ha −1 after experimentation from 46 kg N ha −1 maximum rate during experimentation), in combination with lack of P and K application.…”

“…The lack of yield gain by the top-yielding farmers might imply that at their current management level these farmers could not further raise their grain yields beyond the level observed during joint experimentation, probably because the observed current N input could be too low (which was up to a maximum of 68 kg N ha −1 after experimentation from 46 kg N ha −1 maximum rate during experimentation), in combination with lack of P and K application. It may therefore be necessary that farmers in this production system increase N rates, and P and K application be emphasised based on field inherent fertility to further raise grain yields as current farmers' fertilisation strategies do not put into consideration P and K application (Awio et al, 2022). This should be in addition to improved crop management practices, like proper timing of weeding and fertiliser application.…”

“…The study was conducted in the Doho rice irrigation scheme, where components of recommended agronomic practices (RAP) for rice had been previously tested in researcher led on-farm field trials designed and managed together with farmers (Awio et al, 2022). The Doho rice irrigation scheme is located in Eastern Uganda in the Butaleja district (34…”

“…This study assessed the change in management practices and grain yield of rice farmers 1 year after the end of a 1year joint experimentation, conducted between January and December 2019 on-farm together with farmers, where different components of recommended agronomic practices (RAP) for lowland rice production were tested (Awio et al, 2022). Farm types were identified and characterised based on packages of RAP applied on-farm.…”

Introducing an ecologically-based pest management approach in Cambodia through adaptive learning networks

“…Pest-related effects of wider plant spacing include disease transmission, as well as management of weeds and insects (Castilla and Savary, 2003, Chauhan et al, 2011). Line sowing alongside timely weed management also has yield effects, aside from improved nutrient management (Awio et al, 2022). Such combined effects are typically difficult to measure as many factors are involved and outcomes are conditional on local circumstances.…”