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The demand for rice to meet the dietary need in low-income countries is expected to witness an exponential rise as the population increases. Meeting the rice demand domestically has remained challenging due to significant yield loss caused by several biotic and abiotic factors. Among these factors, one of the most important is the high weed pressure that ravages the upland rice ecology. In Nigeria, several independent weed control techniques, such as physical, chemical and cultural methods, have been recommended and adopted for weed control across varying rice upland ecologies. However, outcomes of these approaches when used independently have not consistently led to an increase in yield. There remains an outstanding deficit between the actual yield and the potential rice yield. This review aimed to identify potential research gaps, and quest effective and sustainable weed management strategies in smallholder upland rice farming systems in Nigeria. A critical analysis of studies suggests the potential of sustainable weed management practices if adopted and adapted smartly in different upland ecologies in Nigeria. Competitiveness of upland rice against weeds can be enhanced through strategic integration of weed competitive cultivars, optimum nitrogen application timings (within weed-free periods), uniform plant spacing, and high seeding rates, with conventional herbicide/manual weed control practices. However, such management practices can only be engaged where inputs are supplied on time and the technical know-how is extended to farmers. The review equally highlights potential research gaps for further studies. [ABSTRACT FROM AUTHOR]

Although different modifications of ridge tillage (RT) systems exist in different regions around the world, the positive impacts of RT on crop yields and weed management are quite similar. This review gives a comprehensive summary of different forms of RT and highlights the benefits of RT for crop growth, mainly due to better access to soil moisture, nutrients and light. In temperate areas, RT can accelerate crop emergence because soil temperature is usually higher on the ridge. These stimulating effects increase crop competitiveness against weeds especially in the early period of crop development until canopy closure. RT with crops placed on the top of ridges can also be used for automatically guiding inter-row hoes and intra-row band sprayers. The ridges can replace automatic vision control systems for hoeing and band spraying, which are needed for precise weeding in conventional flat seedbeds. Therefore, RT can be considered a possible platform for smart/robotic weeding. This paper introduces a new RT system using real-time kinematic (RTK) global satellite navigation systems (GNSS) for the ridging and seeding of maize and soybean on top of recompacted ridges. Straight ridges with precise positioning data were used to guide mechanical weeding elements precisely along the crop rows. Simultaneously, weeds in the valleys were suppressed by living mulches. Field experiments with this new technology in maize showed 85.5% weed dry biomass suppression compared to an untreated control and a slightly higher weed control efficacy than mechanical weeding in flat seedbeds. [ABSTRACT FROM AUTHOR]