Nutrient Management in Rainfed Lowland Rice in the Lao PDR

The International Rice Research Institute (Lao-IRRI Project) and the Lao National Rice Research Program have been collaborating on rice research since 1991. Soil fertility research has been conducted in all provinces of Laos through this effort. The objective of this book is to review the research that has been conducted on nutrient management of lowland rice in Laos from 1991 to 2000 and to present an integrated and sustainable nutrient management approach that is relevant to Lao farmers. We focus on the rainfed lowland rice system as opposed to the irrigated rice system, although references will be made to both. In the first section, an overview of lowland rice trends and practices in Laos will be given This will be followed by a discussion of the production environment, with emphasis on climate and soils. This will be followed by a presentation of research aimed at identifying nutrient deficiencies and nutrient management strategies to overcome these deficiencies. Finally, the last section provides an overall summary and recommendation for different soils. In the appendixes at the end, we have provided (1) a list of Lao-IRRI publications relating to rainfed lowland rice, which are available from IRRI, and (2) a list of soil fertility experiments that have been conducted from 1991 to 2000. It is from these experiments that the results of this book have been derived.

Insights into adoption of farming practices through multiple lenses: an innovation systems approach

A complex systems approach to innovation provides rich insights into the drivers, barriers, and key elements for innovation in rural systems. Through a case study of dry direct seeding (DDS) in smallholder systems in Laos, this article reveals a “perfect storm” of challenges and opportunities resulting in rapid adoption. Labour shortage, climate variability, and machinery availability are key factors. The lessons for the research and development community are that; every local system and situation is unique; focusing on one set of factors is never sufficient; and that timelines for change may be long and require persistence and longer term commitment from donors.This work was supported by the Australian Centre for International Agricultural Research under [Grant Number CSE/2014/ 086]: “Crop-livestock systems platforms for capacity building, testing practices, commercialization and community learning”

Constraints to Rice Production Systems in Laos

In 1999, total rice production in Laos was more than 2.1 million tonnes, enough to make the nation self-sufficient in rice. Over the past 2 decades, total production has increased by about 100%, with most of the increase occurring in the rainfed lowlands where production jumped from 705 000 t in 1980 to 1 502 000 t in 1999. Even though the dry-season irrigated environment has increased production by almost nine times in the past decade (from 41 000 t in 1990 to 354 000 tin 1999) and further small-scale irrigation schemes are planned to achieve a total dry-season irrigated area of about 180 000 ha by 2005, the wet-season lowland environment will remain the most important rice-producing environment for the foreseeable future. Higher yields and reduced year-to-year variability in production can be expected with further intensification of production systems in the lowlands. However, further improvements in production will depend on higher levels of inputs and continued alleviation of some production constraints. The uplands will become less important for rice production as alternative, more sustainable technologies are developed to replace the current ‘slash-and-burn’ and shifting cultivation practices. This paper summarizes the known main abiotic and biotic production constraints in each of Laos’s rice-producing environments: wet-season lowlands, dry-season irrigated, and rainfed uplands, but not those socioeconomic constraints that can also have significant impact on farmer attitudes and production. The major production constraints in the main rice-producing environment—the wet-season lowland ecosystem of the Mekong River Valley—are drought and poor soil fertility. However, more than 10% of the wetseason lowlands in the central and southern agricultural regions are also regularly affected by flooding of the Mekong River. In these areas, flood damage is often regarded as a greater production constraint than drought. In the dry-season irrigated environment, poor soil fertility is the main abiotic constraint. Insect pests are becoming increasingly important in both these production systems. In existing production systems in the rainfed uplands, the main constraints are, in decreasing order of significance, weeds, rodents and drought. Farmers’ perceptions of the relative importance of production constraints in the uplands are generally more accurate than those in the lowlands. Poor soil fertility is often not rated among the most important constraints in the wet-season lowlands and dry-season irrigated environments, despite experimental evidence that often the greatest yield increases can come from improved plant nutrition. Until recently, farmers’ perceptions of the importance of insect pests in the lowlands often exaggerated their economic significance

Integrated nutrient–weed management under mechanised dry direct seeding (dds) is essential for sustained smallholder adoption in rainfed lowland rice (Oryza sativa L.)–Corrigendum

In the above mentioned article, the corresponding author's present address was omitted from the corresponding author information. The corresponding author information should read. On page 7, in Table 2, the decimal points have been mistakenly omitted in column 'Yields for transplanted rice', making the figures 100 times what they should be. This should be the same order of magnitude as the 'Yields for DDS rice'; about 2.0 t/ha'. The corrected Table 2 is displayed below. (Table Presented)

Adaptation of rice (Oryza sativa L.) genotypes in the rainfed lowlands of Lao PDR

Genotype by environment (G×E) interactions for grain yield were investigated in 14 rice genotypes across eight rainfed lowland field environments in Lao PDR, in order to identify stable adapted cultivars for improved farmer livelihood and food security. G×E accounted for 20.3% of the total variance, with three vectors from ordination analysis accounting for 75.1% of the G×E-SS, in 6 genotype × 6 environment groups. PCA1 indicated water-limited yield potential, PCA2 pre-flowering stress and PCA3 post-flowering stress. Genotype groups (G1–G6) differed in adaptation to these environments. G5 (VT450-2 and TSN9) were widely adapted and high-yielding. G6 (TDK11 and TDK37) were also high-yielding, topping the rankings in three environment groups, but yielded less in Phalanxay 2012 and Phalanxay 2011, where their phenology was unstable under stress. Other genotype groups showed specific adaptations, but failed to exceed yields of G5 and G6. Hence, VT450-2 and TSN9 (G5) were the preferred genotypes for rainfed lowland in southern Lao PDR, due to their high and stable grain yields. Stability in flowering time and high yield in rainfall deficit were desirable traits for improved farmer livelihood and food security

Integrated nutrient–weed management under mechanised dry direct seeding (dds) is essential for sustained smallholder adoption in rainfed lowland rice (Oryza sativa L.)

In rainfed lowland rice-based systems, increasing labour scarcity due to off-farm employment is encouraging farmers to switch from transplanting to dry direct seeding (DDS). To assure stable productivity at a level comparable with or superior to transplanting, DDS management must ensure rice seedlings have access to nutrients in order to be competitive with weeds, which must also be suppressed. This paper examined farmer perceptions of DDS using a farmer survey, and used on-farm experiments to examine responses of rainfed lowland rice to integrated nutrient–weed management, based around mechanised DDS. In the survey, weeds were the biggest problem faced by farmers in using DDS (61%). In 90% of cases, farmers reported that weeds had increased under DDS, with most farmers (78%) controlling weeds by hand. All farmers said they would use DDS in the following season (100%), due to labour savings (47%), timeliness of operations, improved productivity, low investment or a combination of these (44%). In on-farm experiments, banding nutrients with the seed at sowing enhanced early dry matter of rice, while early weed dry matter was reduced. Early weed control using ducklings or hand weeding reduced weed competition and increased rice growth, with ducklings providing additional yield benefits over hand weeding. Early increases in seedling vigour of rice, and in weed suppression, carried through to greater dry matter and yield of rice at maturity. Integrated nutrient–weed management in mechanised DDS increased DDS yields, reduced DDS yield variability and contributed to sustainability of DDS rice systems

Short-duration mungbean (Vigna radiata (L.) R. Wilczek) genotypes differ in performance, water use and apparent water-use efficiency in southern Lao PDR

Improving nutrition-sensitive food security is important in low-income, food-deficit nations like Lao PDR, where subsistence farmers rely on a single rainfed lowland rice crop in the wet season. Access to resource conservation technologies, small on-farm water storages and electricity are starting to allow farmers to consider post-rice crops. With water availability still limited, short-duration pulse crops may be viable. This paper examined grain yield and water use during grain filling of eight short-duration mungbean genotypes after rainfed lowland rice at Champhone and Pakse in southern Lao PDR in the 2013 dry season. Two supplementary watering regimes were used, watered every 15 days (at 15, 30 and 45 days), and watered as needed at the first sign of visible wilting (at 23 and 45 days), with three replicates. Soil volumetric water content was measured by time-domain reflectometer. Over two drying cycles, VC1913A, VC3890A and VC7118A used significantly less water than other genotypes at both sites. Genotypes VC7118A and NM94 were higher yielding at Champhone, and VC6310 was higher yielding at Pakse. The relationship between grain yield and water use during grain filling was less straight forward, as it applied within apparent water-use efficiency categories. Overall, VC7118A was superior, due to its effective combination of higher apparent water-use efficiency during grain filling, lower water use in grain filling, and higher grain yield. NM94 also performed well, but required more water for similar yield performance. Drill sowing would allow timely establishment of the post-rice crop to utilize residual soil water in the dry season. These results suggest that mungbeans have a role as a post-rice crop with supplementary irrigation in Lao PDR and comparable environments, to improve nutrition-sensitive food security