Rice production in Tanzania, with 67% of its territory considered semi-dry and having average annual rainfall of 300 mm, must be increased to feed an ever-growing population. Water for irrigation and low soil fertility are among the main challenges. One way to decrease water consumption in paddy fields is to change the irrigation regime for rice production, replacing continuous flooding with alternate wetting and drying. In order to assess the impact of different irrigation regimes and nitrogen fertilizer applications on growth, yield, and water productivity of rice, a greenhouse pot experiment with soil from lowland rice ecology was conducted at Sokoine University of Agriculture, Tanzania during the 2019 cropping season. The experiment was split-plot based on randomized complete block design with 12 treatments and 3 replications. Water regimes were the main factors comparing continuous flooding (CF) and alternate wetting and drying (AWD) with nitrogen fertilizer levels as the subfactor, comparing absolute control (no fertilizer) with 0 (P and K fertilizers), 60, 90, 120, and 150 kg Nha−1. Alternate wetting and drying (AWD) significantly improved water productivity by 8.3% over CF (p < 0.05). Water productivity (WP) ranged from 0.6 to 1.5 kg of rice per m3 of water. Average water use ranged from 36 to 82 L per season, and water saving was up to 34.3%. Alternate wetting and drying significantly improved yields (p < 0.05) by 13.3%, and the yield ranged from 21.8 to 118.2 g pot−1. The combination of AWD water management and 60 kg N ha−1 nitrogen fertilization application was found to be the optimal management, however there was no significant difference between 60 and 90 kg N ha−1, in which case 60 kg N ha−1 is recommended because it lowers costs and raises net income. Nitrogen levels significantly affected water productivity, water use, and number of irrigations. Nitrogen levels had significant effect (p < 0.05) on plant height, number of tillers, flag leaf area, chlorophyll content, total tillers, number of productive tillers, panicle weight, panicle length, 1000-grain weight, straw yield, grain yield, and grain harvest index. The results showed that less water can be used to produce more crops under alternative wetting and drying irrigation practices. The results are important for water-scarce areas, providing useful information to policy makers, farmers, agricultural departments, and water management boards in devising future climate-smart adaptation and mitigation strategies.

Climate change and agriculture are interlinked and affect each other globally. The global population continues to rise while food and nutritional insecurity remain main global challenges facing humanity. Traditional agriculture methods need transformation to climate smart agriculture (CSA) approaches that have potential to improve food production amidst climate change realities. The review aimed at evaluation of published literature on CSA, establishment of CSA linkages with national development plans for Uganda and Ethiopia, African Union Agenda 2063, UN Sustainable Development Goals and CSA contribution to biodiversity conservation across the globe. Additionally, the review aimed at identifying opportunities and challenges of CSA in the 21 st Century and recommend possible options for all stakeholders for improved income, environmental conservation, and food and nutritional security. Literature search from 2000-2019 was carried out using key words and key phrases in relevant journals and authentic websites. It was found out that CSA supports three pillars: 1) Sustainably increasing agricultural productivity and incomes, 2) Adapting and building resilience to climate change, 3) Climate change mitigation and contributes to Biodiversity Conservation and management. CSA approach has potential to improves food security and farmers' income. CSA has a vast number of opportunities that include availability of crop genetic diversity, availability of interested CSA researchers, gene banks for genome resources for CSA crop enhancement; enhanced technology for CSA practices that can be accessed by farmers and vibrant research organizations and donor agencies interested in promoting CSA approaches. CSA challenges were identified to include: limited technical and financial capacity and negative attitude from smallholder farmers. It was concluded that CSA approach is a better option for the present and centuries to come farmers across the globe for the attainment of the United Nations (UN) Sustainable Development Goals (SDGs) 2015-20130, UN Agenda 2063 and national development plants of most African countries including Uganda and Ethiopia. The review recommended that capacity building for farmers and researchers need to be done and governments and donor agencies should provide soft CSA loans to farmers to supporting CSA practices and technologies in all developing countries and the approach should be adopted by all the farmers and be promoted by all stakeholders at all levels in both the present and future centuries.

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In rice production greenhouse gas emission (GHG) reduction is an important task for many countries, Tanzania included. Of global agricultural GHG emitted from rice fields, about 30 and 11% are represented by CH4 and N2O, respectively. For successful climate smart rice cultivation, rice management practices, including nitrogen fertilization are two key crucial components that need evaluation. The objective of this study was to evaluate the crop management practices and N fertilization on yield and greenhouse gases emission in paddy rice production, Experiments were designed in split-plot randomized complete block and replicated three times. Two rice management practices namely conventional practice (CP) and system of rice intensification (SRI) and six rates of nitrogen fertilizer (absolute control, 0, 60, 90,120 and 150 kg N ha−1) were applied in two consecutive seasons. The Source-selective and Emission-adjusted GHG CalculaTOR for Cropland (SECTOR) was used to calculate the GHG emission. Methane emission was in the range of 88.7–220.6 kg ha−1season−1, where higher emission was recorded in CP treatments (ABC, CP 0 and CP 120N) compared to SRI treatments. SRI reduced methane and carbon dioxide emission by 59.8% and 20.1% over CP, respectively. Seasonal nitrous oxide emissions was in the range of no detected amount to 0.0002 kgN2O ha−1 where SRI treatments recorded up to 0.0002 kgN2O ha−1 emissions while in CP treatment no amount of N2O was detected. The interaction of system of rice intensification and 90 kg N ha−1 (SRI90N) treatment recorded higher grains yield (8.1, 7.7 t ha−1) with low seasonal global warming potential (GWP) (3,478 and 3,517 kg CO2e ha−1) and low greenhouse gas intensity (0.42, 0.45 kg CO2e per kg paddy) compared to other treatments in wet and dry season, respectively. Therefore, SRI with 90 kg N was the treatment with mitigation potential and reduced GWP without compromising rice yield.