Increasing paddy yields and improving farm management: results from participatory experiments with good agricultural practices (GAP) in Tanzania

Abstract

Rice is an increasingly important commodity in sub-Saharan Africa. In Tanzania, the rice yield gap is as high as 87%, due to a combination of production constraints and sub-optimal crop management. Reducing this yield gap may be partly achieved through the introduction and dissemination of good agricultural practices (GAP). We conducted 18 farmer-managed onfarm trials in Tanzania, to test a set of GAP components against conventional farmers' practices (FP) for two consecutive growing seasons in 2013 and 2014. The objectives were: (1) to understand farmers' capabilities in implementing GAP; (2) to acquire better insights into the merits, relevance and suitability of individual GAP components; and (3) to provide a case study showing that exposure to good practices combined with the farmers' own experimentations can serve to improve and, trigger a positive change in the participating farmers' crop management. Compared to the farmers' own practices, average yield increases of 1 t paddy ha −1 in 2013 and 2.7 t ha −1 in 2014 were achieved when following GAP. These yield advantages were mainly obtained by a higher panicle number, improved harvest index and improved weed control. Farmers experienced difficulties with land levelling, planting or sowing in lines and using rotary weeders, but they were convinced that these technologies are important to boost their rice yields. The case of Tanzania shows that paddy yields can be substantially improved by GAP and that adoption of GAP by smallholder rice farmers can be triggered by stimulating experimentations with such practices on their own farms.

Quantifying rice yield gaps and their causes in Eastern and Southern Africa

“…Improved modern varieties such as NERICA‐4, Primavera and B22 were used at Ankazomiriotra in Madagascar (88%), variety Saro‐5 at Kahama (13%) and Kilombero (38%) in Tanzania, and variety K98 at Doho (36%) in Uganda. A recent study from Kilombero observed Kisekese, Kalamata and Super India to be among the most popular local varieties (Senthilkumar et al., 2018). The poor adoption rates of improved modern rice varieties in ESA have been attributed to the mismatch in terms of farmer and consumer grain quality preferences (Meertens, Ndege, & Lupeja, 1999; Nhamo et al., 2014) and more recently to sub‐optimal adaptation to occurring climate extremes and poor performance following erratic crop management that is often observed at smallholder farms (Sekiya, Tomitaka, Oizumi, Assenga, & Jacob, 2015).…”

“…At Kilombero in Tanzania, compared to the weed‐free fields, presence of a below canopy weed cover ranging from less than 10 to more than 60% reduced the yield by 3.6 to 4.4 t/ha. Good land levelling and timely weed control are components of good agricultural practices recommended to avoid yield losses (Rodenburg & Johnson, 2009; Senthilkumar et al., 2018). In the irrigated lowland of Ambohibary, compared to direct seeding, yield reduced with 1.74 t/ha by transplanting.…”

“…Demands for rice in Eastern and Southern Africa (ESA) are rapidly increasing because of changes in consumer preferences and urbanization (Balasubramanian, Sie, Hijmans, & Otsuka, 2007; FAO, 2018). However, local rice production lags behind consumption, and this is mainly due to the low yield levels attained on smallholder farms (van Ittersum et al., 2016; van Oort et al., 2015; Senthilkumar, Tesha, Mghase, & Rodenburg, 2018). Low rice yield levels at African smallholder farms are caused by abiotic stresses such as drought, nutrient deficiencies and/or toxicity, cold and heat (Haefele et al., 2013; Kijoji et al., 2012; Nhamo, Rodenburg, Zenna, Makombe, & Luzi‐Kilhupi, 2014; Poussin, Wopereis, Debouzie, & Maeght, 2003; Saito et al., 2019; Saito et al., 2013; Saito, Diack, Dieng, & Ndiaye, 2015; Saito, Dieng, Toure, Somado, & Wopereis, 2015; Tanaka et al., 2017) and biotic stresses such as birds (De Mey, Demont, & Diagne, 2012), insect pests, diseases and weeds (Adesina, Johnson, & Heinrichs, 1994; Diagne et al., 2013; Rodenburg & Johnson, 2009; Rodenburg et al., 2019).…”

“…Low rice yield levels at African smallholder farms are caused by abiotic stresses such as drought, nutrient deficiencies and/or toxicity, cold and heat (Haefele et al., 2013; Kijoji et al., 2012; Nhamo, Rodenburg, Zenna, Makombe, & Luzi‐Kilhupi, 2014; Poussin, Wopereis, Debouzie, & Maeght, 2003; Saito et al., 2019; Saito et al., 2013; Saito, Diack, Dieng, & Ndiaye, 2015; Saito, Dieng, Toure, Somado, & Wopereis, 2015; Tanaka et al., 2017) and biotic stresses such as birds (De Mey, Demont, & Diagne, 2012), insect pests, diseases and weeds (Adesina, Johnson, & Heinrichs, 1994; Diagne et al., 2013; Rodenburg & Johnson, 2009; Rodenburg et al., 2019). The sub‐optimal crop management practices followed by rice farmers in this region only sustain or aggravate this situation (Saito et al., 2013; Senthilkumar et al., 2018; Tanaka, Saito, Azoma, & Kobayashi, 2013).…”

Analysis of rice yield response to various cropping seasons to develop optimal cropping calendars in Mwea, Kenya

“…In general, the cropping calendar for double or triple rice is tight as each location has a climatically inappropriate period for rice cultivation. To narrow the yield gap in farmers' field and to achieve yield ceiling (potential) of high-yielding varieties, introducing good agricultural practices (GAP), an integrated set of the recommended crop, soil, water, and weed management practices (Senthilkumar, Tesha, Mghase & Rodenburg, 2018), is important. Selection of the most appropriate cropping calendar should be a component of GAP.…”