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Alternate wetting and drying irrigation maintained rice yields despite half the irrigation volume, but is currently unlikely to be adopted by smallholder lowland rice farmers in Nepal

View Article: PubMed Central - PubMed

ABSTRACT

Alternate wetting and drying (AWD) irrigation can save water while maintaining rice yields, but in some countries its adoption by farmers remains limited. Key knowledge gaps include the effect of AWD on early vegetative vigor and its relationship with yield; the effects of AWD on yield and water use efficiency of local cultivars used by smallholder farmers; and the socio‐economic factors influencing current irrigation scheduling. To address these questions, an on‐farm field trial of dry‐season (chaite) rice, comparing two locally important cultivars (Hardinath‐1 and CH‐45) under AWD imposed from 1 week after transplanting to flowering and continuous flooding (CF), was carried out in Agyauli in the central Terai region of Nepal, and triangulated with social research methods exploring the rationale for current irrigation scheduling and perceptions of AWD. Although AWD plots received on average 57% less irrigation water than CF plots, yields did not significantly differ between irrigation treatments, indicating that AWD could considerably enhance crop water use efficiency in this region. In the earlier flowering, more vigorous CH‐45, there were no treatment differences in any yield component while in the later flowering Hardinath‐1, an 11% decrease in filled grain number was compensated by a 14% increase in the percentage of effective tillers per hill. Although leaf elongation rate on the main tiller did not differ between treatments, tillering and green fraction (a measure of canopy closure) were significantly higher under AWD. Surveys established that most local farmers are already using a local adaptation of AWD to modify irrigation volumes, in some cases in response to a limited and unreliable water supply. However, farmers have few direct incentives to reduce overall water use under current water governance, and formal AWD practices are therefore unlikely to be adopted despite their viability as a water‐saving irrigation technique.

No MeSH data available.


Daily rainfall in mm for Agyauli (bars) and treatment imposition of alternate wetting and drying (AWD) in two cultivars (Hardinath‐1 and CH‐45) from 8 to 84 days after transplanting. Lines show mean daily soil water depth in mm in AWD plots in the two cultivars, with dashed grey line indicating soil surface. Horizontal bars at top show periods for which AWD (white) was imposed for the two cultivars, and when they were continuously flooded (CF) during flowering (grey), in line with IRRI recommendations.
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fes358-fig-0001: Daily rainfall in mm for Agyauli (bars) and treatment imposition of alternate wetting and drying (AWD) in two cultivars (Hardinath‐1 and CH‐45) from 8 to 84 days after transplanting. Lines show mean daily soil water depth in mm in AWD plots in the two cultivars, with dashed grey line indicating soil surface. Horizontal bars at top show periods for which AWD (white) was imposed for the two cultivars, and when they were continuously flooded (CF) during flowering (grey), in line with IRRI recommendations.

Mentions: Four replications of two irrigation treatments (CF and AWD) and two locally commonly grown improved cultivars (CH‐45 and Hardinath‐1) were laid out in a randomized arrangement of 4 m x 4 m square plots, with 2 m wide irrigation channels and 1 m spacings, and earth bunds built around each plot according to local practices. The field, which was fallow over the winter, was prepared using a buffalo‐pulled plow and puddler and farmyard manure and 46 kg ha−1 each of diammonium phosphate and urea were applied prior to transplanting. Transplanting was carried out using local planting densities and spacings (mean number of seedlings per hill = 5, mean spacing between hills = 160 mm). The crop was top dressed with a further 60 kg ha−1 urea and a stemborer infestation treated with chemical insecticide at 36 days after transplanting. Heading occurred in CH‐45 and Hardinath‐1 from 32 and 51 days after transplanting, respectively, and both cultivars were harvested on Day 88. During the production cycle, mean maximum and minimum temperatures were 37°C and 26°C respectively; and mean relative humidity was 72% (meteorological data courtesy of Nepal Department of Meteorology and Hydrology). Rainfall was infrequent during the first 60 days after transplanting and more frequent thereafter as the monsoon arrived (Fig. 1).


Alternate wetting and drying irrigation maintained rice yields despite half the irrigation volume, but is currently unlikely to be adopted by smallholder lowland rice farmers in Nepal
Daily rainfall in mm for Agyauli (bars) and treatment imposition of alternate wetting and drying (AWD) in two cultivars (Hardinath‐1 and CH‐45) from 8 to 84 days after transplanting. Lines show mean daily soil water depth in mm in AWD plots in the two cultivars, with dashed grey line indicating soil surface. Horizontal bars at top show periods for which AWD (white) was imposed for the two cultivars, and when they were continuously flooded (CF) during flowering (grey), in line with IRRI recommendations.
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Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4998133&req=5

fes358-fig-0001: Daily rainfall in mm for Agyauli (bars) and treatment imposition of alternate wetting and drying (AWD) in two cultivars (Hardinath‐1 and CH‐45) from 8 to 84 days after transplanting. Lines show mean daily soil water depth in mm in AWD plots in the two cultivars, with dashed grey line indicating soil surface. Horizontal bars at top show periods for which AWD (white) was imposed for the two cultivars, and when they were continuously flooded (CF) during flowering (grey), in line with IRRI recommendations.
Mentions: Four replications of two irrigation treatments (CF and AWD) and two locally commonly grown improved cultivars (CH‐45 and Hardinath‐1) were laid out in a randomized arrangement of 4 m x 4 m square plots, with 2 m wide irrigation channels and 1 m spacings, and earth bunds built around each plot according to local practices. The field, which was fallow over the winter, was prepared using a buffalo‐pulled plow and puddler and farmyard manure and 46 kg ha−1 each of diammonium phosphate and urea were applied prior to transplanting. Transplanting was carried out using local planting densities and spacings (mean number of seedlings per hill = 5, mean spacing between hills = 160 mm). The crop was top dressed with a further 60 kg ha−1 urea and a stemborer infestation treated with chemical insecticide at 36 days after transplanting. Heading occurred in CH‐45 and Hardinath‐1 from 32 and 51 days after transplanting, respectively, and both cultivars were harvested on Day 88. During the production cycle, mean maximum and minimum temperatures were 37°C and 26°C respectively; and mean relative humidity was 72% (meteorological data courtesy of Nepal Department of Meteorology and Hydrology). Rainfall was infrequent during the first 60 days after transplanting and more frequent thereafter as the monsoon arrived (Fig. 1).

View Article: PubMed Central - PubMed

ABSTRACT

Alternate wetting and drying (AWD) irrigation can save water while maintaining rice yields, but in some countries its adoption by farmers remains limited. Key knowledge gaps include the effect of AWD on early vegetative vigor and its relationship with yield; the effects of AWD on yield and water use efficiency of local cultivars used by smallholder farmers; and the socio‐economic factors influencing current irrigation scheduling. To address these questions, an on‐farm field trial of dry‐season (chaite) rice, comparing two locally important cultivars (Hardinath‐1 and CH‐45) under AWD imposed from 1 week after transplanting to flowering and continuous flooding (CF), was carried out in Agyauli in the central Terai region of Nepal, and triangulated with social research methods exploring the rationale for current irrigation scheduling and perceptions of AWD. Although AWD plots received on average 57% less irrigation water than CF plots, yields did not significantly differ between irrigation treatments, indicating that AWD could considerably enhance crop water use efficiency in this region. In the earlier flowering, more vigorous CH‐45, there were no treatment differences in any yield component while in the later flowering Hardinath‐1, an 11% decrease in filled grain number was compensated by a 14% increase in the percentage of effective tillers per hill. Although leaf elongation rate on the main tiller did not differ between treatments, tillering and green fraction (a measure of canopy closure) were significantly higher under AWD. Surveys established that most local farmers are already using a local adaptation of AWD to modify irrigation volumes, in some cases in response to a limited and unreliable water supply. However, farmers have few direct incentives to reduce overall water use under current water governance, and formal AWD practices are therefore unlikely to be adopted despite their viability as a water‐saving irrigation technique.

No MeSH data available.