Search Results (3)

Mangrove swamp rice production (MSRP) refers to rice cultivation in former mangrove soils that have been anthropogenically modified for food production. The method utilizes the largest possible storage of fresh water to desalinate the soils and make them productive. However, temporal variability in rainfall patterns causes loss of efficiency in production, impacting crop growth and reducing productivity. To improve MSRP, it is necessary to identify the primary constraints associated with salinity, enhancing and maximizing freshwater storage efficiency and water productivity. This study provides a general description of the MSRP system in both the northern and southern regions of Guinea-Bissau, aiming at the identification of the main water management limitations. The description involves the use of typologies and the identification of zones with specific characteristics within the paddies. Furthermore, this review includes an analysis of the physicochemical characteristics of soils in relation to salinity issues, descriptions of agronomic management, rice varieties, and the significance of managing dikes and bunds to improve mangrove swamp rice water management. This study shows how the MSRPS is characterized by dynamism and complexity, involving a wide range of constraints associated with salinity features, cultural influences, and microclimatic conditions that are subject to temporal variations. Full article

Since 2002, Vietnam has implemented rice contract-farming policies to develop the linkage among stakeholders in the agricultural sector; however, there is very low participation of farmers. Therefore, this study aims to determine the perception on both advantages and disadvantages of rice contract farming (RCF); identify the reasons for non-participation and drop-out of rice contract farming; and indicate the typology of contract by using data from documentation, key informant interviews, and focus group discussions. The results indicate that farmers considered the guaranteed output price and stable income as the most advantages of RCF while the main disadvantages were reducing the household’s freedom or losing flexibility in making decisions on-farm production, management, and selling product; possible delays in payments, in input delivery, in harvesting, and output delivery. In addition, farmers did not want to participate in RCF because of reducing the household’s freedom in making decisions, not complying with RCF, not trusting cooperatives as well as enterprises, and because selling paddy to middlemen is easier and simpler. Farmers dropped out of RCF because the contracting companies breached the contract provisions. Farmers mentioned many provisions of the contract but the most important to them were payment, price options, and delivery arrangement. Full article

Salinization is a major soil degradation threat in irrigated systems worldwide. Irrigated systems in the Niger River basin are also affected by salinity, but its spatial distribution and intensity are not currently known. The aim of this study was to develop a method to detect salt-affected soils in irrigated systems. Two complementary approaches were tested: salinity assessment of bare soils using a salinity index (SI) and monitoring of indirect effects of salinity on rice growth using temporal series of a vegetation index (NDVI). The study area was located south of Niamey (Niger) in two irrigated systems of rice paddy fields that cover 6.5 km². We used remote-sensing and ground-truth data to relate vegetation behavior and reflectance to soil characteristics. We explored all existing Sentinel-2 images from January 2016 to December 2019 and selected cloud-free images on 157 dates that covered eight successive rice-growing seasons. In the dry season of 2019, we also sampled 44 rice fields, collecting 147 biomass samples and 180 topsoil samples from January to June. For each field and growing season, time-integrated NDVI (TI-NDVI) was estimated, and the SI was calculated for dates on which bare soil conditions (NDVI < 0.21) prevailed. Results showed that since there were few periods of bare soil, SI could not differentiate salinity classes. In contrast, the high temporal resolution of Sentinel-2 images enabled us to describe rice-growing conditions over time. In 2019, TI-NDVI and crop yields were strongly correlated (r = 0.77 with total biomass yield and 0.82 with grain yield), while soil electrical conductivity was negatively correlated with both TI-NDVI (r = −0.38) and crop yield (r = −0.23 with total biomass and r = −0.29 with grain yield). Considering the TI-NDVI data from 2016–2019, principal component analysis followed by ascending hierarchical classification identified a typology of five clusters with different patterns of TI-NDVI during the eight growing seasons. When applied to the entire study area, this classification clearly identified the extreme classes (i.e., areas with high or no salinity). Other classes with low TI-NDVI (i.e., during dry seasons) may be related to areas with moderate or seasonal soil salinity. Finally, the high temporal resolution of Sentinel-2 images enabled us to detect stresses on vegetation that occurred repeatedly over the growing seasons, which may be good indicators of soil constraints due to salinity in the context of the irrigated paddy systems of Niger. Further research will validate the ability of the method developed to detect moderate soil salinity constraints over large areas. Full article