Irrigated Lowland Research Articles

"Biomass Yields and Nutritive Composition of Leucaena Varieties in Irrigated Lowland of Dassench Woreda of South Omo, South-Western Ethiopia"

"Biomass Yields and Nutritive Composition of Leucaena Varieties in Irrigated Lowland of Dassench Woreda of South Omo, South-Western Ethiopia"

Assessing rice production sustainability performance indicators and their gaps in twelve sub-Saharan African countries.

The benchmarking and monitoring of rice production performance indicators are essential for improving rice production self-sufficiency, increasing profitability, reducing labor requirements, optimizing fertilizer inputs, engaging youths in rice production, and increasing the overall sustainability of smallholder rice production systems in countries in sub-Saharan Africa (SSA). In this paper, we quantified five sustainability performance indicators (grain yield, net profit, labor productivity, and nitrogen (N) and phosphorus (P) use efficiencies) to benchmark rice production systems in SSA. Data were collected between 2013-2014 from 2907 farmers from two rice production systems (irrigated and rainfed lowlands) across five agroecological zones (arid, semiarid, humid, subhumid and highlands) in 12 countries (Benin, Cameroon, Cote d'Ivoire, Ghana, Madagascar, Mali, Niger, Nigeria, Senegal, Sierra Leone, Tanzania and Togo). The exploitable gap for each indicator (the difference between the mean of 10 % highest-yielding farms and the mean-yielding farms) was calculated across the countries, the two production systems and agroecological zones. The mean yield varied widely between 2.5 to 5.6 t ha-1 and 0.6 to 2.3 t ha-1 in irrigated and rainfed lowlands, respectively, with an average yield of 4.1 and 1.4 t ha-1, respectively. Across the country-production system combinations, there were yield gaps of 29-69 %, profit gaps of 10-89 %, and labor productivity gaps reaching 71 %. Yield, profit, and labor productivity were positively correlated. They were also positively correlated with N and P fertilizer application rate, but not with N and P use efficiencies. Only between 34-44 % of farmers had desirable ranges in N- or P-use efficiencies in the two production systems. All sites for rainfed lowlands were characterized by low-yield and large gaps in yield, profit, and labor productivity, whereas irrigated lowlands in some countries (Madagascar, Mali, and Togo) have similar characteristics as rainfed ones. We conclude that there is an urgent need to disseminate precision nutrient management practices for optimizing nutrient use efficiency and enhancing rice performance indicators especially in rainfed lowlands as well as low-yielding irrigated lowlands. Furthermore, we propose recommendations for specific categories (i.e. farmer, rice production system, agroecological zone and country) to close performance indicator gaps and to allow the production at scale to achieve rice self-sufficiency in SSA.

Rice yield and economic response to micronutrient application in Tanzania

• Foliar fertiliser application is only effective under drought-free conditions. • Sole application of micronutrients (Zn-B-Mg-S) is not effective in any environment. • Compared to NPK alone, yield increased 0.5–1.8 t ha –1 from NPK + micronutrients. • Micronutrient application to soil or foliar is profitable with adequate soil moisture. Nutrient deficiencies limit rice production in sub-Saharan Africa. The conventional recommended remedy for this is the soil application of fertilizers composed of the macro-nutrients, N, P and K, whereas crop micronutrient requirements are neglected. This leads to nutrient mining and diminished fertiliser use efficiency. Application of micronutrients along with recommended NPK fertiliser rates can prevent nutrient mining and boost rice yields. In this study, we assessed the productivity and profitability of different soil- and foliar-applied micronutrients in 30 on-farm trials per year for two consecutive years (2015, 2016) in Tanzania, East Africa. Five locally available foliar formulations (combinations of macro- and micronutrients or micronutrients alone) and soil application of micronutrients (3−2−7.5−10 Zn-B-Mg-S kg ha –1 ) were assessed under two NPK-fertilization regimes (80−17.5−33.2 and 0−0−0 kg N-P-K ha –1 ) in three rice growing environments (RGEs): Irrigated Lowland (IL), Rainfed Lowland (RL), and Rainfed Upland (RU). The effect of foliar and soil applied micronutrients on yield was consistent in IL but was highly variable in the RL and RU conditions across years. The soil application of micronutrients in the absence of NPK was ineffective in any of the RGEs. In IL, without NPK, foliar application alone increased yield by 0.3−0.4 t ha –1 , compared to control (3.1 t ha –1 ). Only NPK application increased yield by 1 t ha –1 , while NPK and micronutrients application increased yield by 1.5 t ha –1 , compared to control. The benefit-cost (B:C) ratio for NPK with soil applied micronutrients was 4–4.5 compared to NPK application alone. In RL, application of NPK alone increased yield in 2015 from 2.7 to 5.0 t ha –1 while NPK and soil applied micronutrients application increased yield to 6.8 t ha –1 . However, a drought incidence in 2016 nullified this effect. With NPK, two foliar products (F2 and F3) increased yield significantly by 1 t ha –1 . The highest B:C ratio was obtained with soil applied micronutrients (B:C of 14), and two of the foliar products obtained a B:C ratio of 7 and 7.2, respectively. In RU, no significant yield differences were observed among treatments in any year, likely due to drought. Foliar application was effective only under drought-free conditions across the rice growing environments. This study demonstrated that soil applied micronutrients together with NPK significantly increased yields in IL and RL in the absence of drought-stress. Application of macronutrients is a likely prerequisite for maximizing the benefits of applying micronutrients to increase rice yields in Tanzania.

Application of infrared spectroscopy for estimation of concentrations of macro- and micronutrients in rice in sub-Saharan Africa

Determination of the concentration of nutrients in the plant is key information for evaluating crop nutrient removal, nutrient use efficiency, fertilizer recommendations guidelines, and in turn for improving food security and reducing environmental footprints of crop production. Diffuse infrared (IR) reflectance spectroscopy is a powerful, rapid, cheap, and less pollutant analytical tool that could be substituted for traditional laboratory methods for the determination of the concentration of nutrients in plants. However, its accuracy for predicting the concentration of nutrients in rice plants is poorly known. This study aimed i) to determine macro- and micronutrients concentration that can be accurately predicted by near-infrared (NIR, 7498–4000 cm−1), mid-infrared (MIR, 4000–600 cm−1), or their combination (NIR-MIR, 7498–600 cm−1) spectra, ii) to identify the most suitable spectral range with the best prediction potential for the simultaneous analysis of nutrients concentrations in rice plants (straw and paddy) and iii) to assess the influence of agro-ecological zone and production system on nutrients concentrations in straw and paddy (unhulled grains) samples. Second-derivative spectra were fitted against plant laboratory reference data using partial least-squares regression (PLSR) to estimate six macronutrients (N, P, K, Ca, Mg, and S) and seven micronutrients (Na, Fe, Mn, B, Cu, Mo, and Zn) concentration in paddy and rice straw samples collected at harvest from 1628 farmers’ fields in 20 sub-Saharan African (SSA) countries. The modeling prediction potential was assessed by coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), and ratio of performance to interquartile distance (RPIQ). Good prediction models (0.75 < R2 ≤ 0.95) were obtained for 7 nutrients concentrations consisting of N, P, K, Ca, Mg, Mn, and Cu. Satisfactory predictions (0.62 ≤ R2 ≤ 0.75) were obtained for S, Fe, and B. NIR, MIR, and combined NIR-MIR diffuse reflectance spectroscopy demonstrated the best prediction potential for 3, 1, and 6 of these 10 well-predicted nutrients concentrations, respectively. All nutrients concentrations both in straw and paddy were moderate to highly variable (CV = 15–111%). Agro-ecological zone and production system had a significant impact on most nutrients concentrations both in rice straw and paddy. N, P, and K concentrations in rice in irrigated lowland (IL) fields were higher than in rainfed lowland (RL) and upland (RU). From the studied fields, 2%, 16%, and 16% of straw samples were deficient in N, P, and K, respectively. K deficiency occurred in all three production systems, whereas P deficiency mainly occurred in the rainfed upland systems. Overall, the combined NIR-MIR diffuse reflectance spectroscopy has a good potential to be applied as an alternative method in the determination of macronutrient concentrations in rice plants. Further investigation on the relationships between soil attributes, rice productivity, and nutrients concentration data determined in this study is needed for providing fundamental information for site-specific soil management and fertilizer recommendations in SSA.

ALTERNATE WETTING AND DRYING TECHNIQUE AND ITS IMPACTS ON RICE PRODUCTION

The agriculture sector has been facing challenges due to climate change particularly increasing global water scarcity which threatens irrigated low land rice production. Alternate Wetting and drying (AWD) is a water management system where rice fields are not continuously submerged and the fields are allowed to dry intermittently during the rice-growing period. AWD technique is a necessity for modern farming of rice as it is profitable over the continuous flooding irrigation system which prevents the wastage of scarce and vital water resources, irrigation cost and protects the environment from degradation. It also protects human health from diseases like Malaria as there is an absence of continuous flooding for the mosquito to lay eggs. It helps to enhance food security by increasing the production, nutrient content, and minimizing the toxic elements in rice. However, if this technique is not done properly in the field from time to time, we can also get negative impacts. It varies according to soil condition, irrigation timing, environment, etc.

Performance of Five Rice (Oryza sativa L.) Varieties as Influenced by Crop Establishment under Irrigated Lowland Conditions

This study aimed to determine the growth and yield performance of five rice varieties under the different crop establishments and assess rice profitability as influenced by crop establishment under irrigated lowland conditions. The study was laid out in a split-plot arranged in an RCBD with three replications. Crop establishment was designated as the main plot while rice varieties as a subplot. Results revealed that the direct row seeding method significantly showed a significant advantage in agronomic and yield and yield component parameters over the transplanting method among rice varieties tested. Heirloom red rice significantly headed earlier (63.17 days) when planted in both crop establishments and obtained the tallest plant height, greater leaf area index, the heavier weight of 1,000 grains, and grain yield. There was a significant interaction effect on crop establishment and rice variety recorded from sowing to heading and maturity. Cost and return analysis revealed that the direct row seeding method achieved higher gross income (USD 2,012.00) and gross margin (USD 1,086.60) than the transplanting method. Heirloom red rice significantly achieved the highest grain yield (5.85 t ha-1), resulting in a higher gross income and gross margin of USD 2,340.00 and USD 1,352.45, respectively. Direct row seeding is applicable as an effective cost-reducing method of crop establishment for lowland rice production. Besides, it can shorten the time of crop establishment. Heirloom red rice with dual characteristics as an irrigated lowland and upland rice cultivar is feasible for direct row seeding and transplanting methods during the dry season.

Climate-human-landscape interaction in the eastern foothills of Mt. Kilimanjaro (equatorial East Africa) during the last two millennia

The Mt. Kilimanjaro region is known for its long history of intensive agriculture, but the temporal extent of human activity and its impact on the regional ecosystem are not well known. In this study, climate-human-landscape interactions during the past ~2200 years were examined using climate and vegetation proxies extracted from the continuous and high-resolution sediment record of Lake Chala. Ancient-to-modern regional human activity is documented against a backdrop of long-term vegetation dynamics in the low-elevation savanna woodland southeast of Mt. Kilimanjaro and riparian forest within Chala crater. During prolonged dry periods (~1170–1300 CE), succulent dry crater forest expanded relative to the moist lakeshore forest. The savanna landscape surrounding Chala crater was relatively stable through time, except that savanna grasses were stimulated by higher precipitation, consistent with the fuel-limited fire regime evidenced in the charcoal record. Expansion of subalpine ericaceous vegetation and a general decline in Afromontane forest taxa on Mt. Kilimanjaro after 550 CE may reflect a lowering of its upper forest line. The earliest robust signature of human influence on regional vegetation involves an increase in ruderal (weedy) plant taxa around 1100 CE, possibly associated with the development of Chagga homegardens and associated agroforestry in the submontane forest zone. A first hint of cereal agriculture (likely sorghum) is observed around 1550 CE, followed by a more robust signature from 1780 CE onwards which likely reflects the start of lowland irrigation agriculture. From 1780 CE we also find the first undisputed appearance of maize, introduced to East Africa about a century earlier.

Decomposing rice yield gaps into efficiency, resource and technology yield gaps in sub-Saharan Africa

Abstract Meeting current rice demand in sub-Saharan Africa (SSA) requires narrowing yield gaps on currently available agricultural land. The objectives of this study were to decompose rice yield gaps into efficiency, resource and technology yield gaps and to identify priority areas for research and development in the major rice production systems (irrigated lowland, rainfed lowland, and rainfed upland) in SSA. Data were collected during the 2012–2015 wet seasons on soil properties, field operations and yields in 1529 fields at 34 sites in 20 countries using a standardized protocol. Stochastic frontier analysis using data on biophysical environment and fertilizer management practices together with a crop simulation model (ORYZA2000) was used to quantify the yield gap, and efficiency, resource, and technology yield gaps. Cluster analysis was performed to classify the site-production system combinations into yield gap groups. Actual rice yields were on average 3.8, 2.6 and 1.7 t/ha in irrigated lowland, rainfed lowland, and rainfed upland, respectively. The yield yap ranged from 2.0–10.0 t/ha across site-production system combinations while the efficiency, resource, and technology yield gaps varied between 0.9 to 5.7, 0.1 to 2.3 and 0 to 7.5 t/ha, respectively. On average, efficiency, resource, and technology yield gaps accounted for 23, 5 and 37 % of the benchmark yield (potential yield in irrigated lowland or water-limited potential yield in rainfed lowland and upland). Four yield gaps groups were identified and were related to the production systems, soil properties, and fertilizer application. Narrowing yield gaps requires the dissemination of integrated crop management practices in yield gaps groups with a large efficiency yield gap, whereas, in yield gaps groups with a large technology yield gap, the development of technologies to improve soil properties and fertilizer use should be given priority.

An Econometric Study of Production Efficiency Among Rice Farmers In Irrigated Lowland Villages In Java, Indonesia

An Econometric Study of Production Efficiency Among Rice Farmers In Irrigated Lowland Villages In Java, Indonesia

Growth and yield of new hybrid rice in irrigated and rain-fed lowlands

Two experiments were conducted at (i) irrigated lowland, village of Bojong, Cikembar, Sukabumi Sub-district, Indonesia, from November 2011 to February 2012, and (ii) rain-fed lowland, village of Sanca, Gantar sub-district, Indramayu, Indonesia, from April to July 2012. The objective of the experiment was to determine the yield of drought-tolerant hybrid rice genotypes. A randomized block design with three replications was used. The treatment consisted of 8 hybrid rice genotypes (BI485A/BP3, BI485A/BP5, BI485A/BP10, BI485A/BP12, BI485A/BP15, BI599A/BP5, BI599A/BP15 and BI665A/BP6) and 2 check varieties (Hipa 7 and Ciherang) for the experiment in irrigated lowland, 4 hybrid genotypes (BI485A/BP3, BI485A/BP12, BI485A/BP15 and BI599A/BP15) and 3 check varieties (Hipa 7, IR64 and Limboto) for the experiment in rain-fed lowland. On irrigated lowland, all tested-genotypes produced grain yield per hectare, which was not significantly different from the check varieties Ciherang and HIPA 7. The yield of genotype BI485A/BP12, BI485A/BP15 and BI559A/BP15 under irrigated lowland showed non-significant different with check varieties Ciherang and Hipa 7, i.e 5.63, 6.87, and 6.30 tons ha-1, respectively. Genotype BI599A/BP15 under severe drought rain-fed lowland yielded 0.90 tons of grain ha-1, whereas Hipa 7 (hybrid variety, suitable for rain-fed lowland) and Limboto (drought-tolerant check variety) reached 0.34 and 0.29 tons ha-1, respectively. Genotype BI599A/BP15 is a new hybrid genotype that potential for advanced development in rain-fed lowland and in irrigated lowland with a high yield potential and quiet early-maturity age.

Field resistant test of new superior varieties of rice in lowland irrigation agroecosystem against rice blast disease

Rice blast disease is one of the main problems for increasing rice production in Indonesia. It can be controlled by planting new superior varieties of rice. Therefore the rotation of varieties is very important. The research aims to obtain disease control methods through the use of new superior varieties (VUB) of lowland rice. The study was carried out in Sambasule, Meluhu Sub-district, Konawe District, Southeast Sulawesi during the rainy season of 2016. The experiment was arranged in a randomized block design (RBD) with seven treatments and four replications. Each plot was 50 m × 50 m, so the total land area of the experiment was 10,000 m2. Plants were maintained through the Integrated Crop Management (IPM) of lowland rice approach. Disease incidence of the rice blast was observed based on the Standard Evaluation System of rice from the International Rice Research Institute (IRRI). The results showed that Inpari 32, Inpari Blas, Inpari 22 and Ciherang were moderately resistant to leaf blast and insignificantly different to Inpari 26, Inpari 27 and IPB4S. In addition, Inpari 32 is moderately resistant to neck blasts and insignificantly different to Inpari 22, Inpari Blas and Ciherang.

Partitioning of total soil respiration into root, rhizosphere and basal-soil CO2 fluxes in contrasting rice production systems

Soil respiration contributes significantly to ecosystem respiration and is vital in the context of climate change research. In a season-long experiment we studied total soil respiration (TSR) and its partitioning into root respiration, rhizospheric respiration (RhR) and basal-soil respiration in four contrasting rice production systems: irrigated lowland (IL) (cv. Gayatri); organic nutrient managed irrigated lowland (OIL) (cv. Geetanjali); system of rice intensification (SRI) (cv. Swarna); and aerobic rice system (Aerobic) (cv. APO). We considered TSR to be the sum of root respiration, RhR and basal-soil respiration. Irrespective of the rice production system, TSR was higher at panicle initiation stage. Considering all four systems, the RhR contributed the most (59–83%) and basal-soil respiration the least (10–19%) to the TSR. Mean RhR showed the trend of Aerobic &amp;gt; SRI &amp;gt; IL &amp;gt; OIL across the growing seasons and indicated higher rhizosphere activities in the aerobic system. Mean root respiration showed a trend of IL &amp;gt; OIL &amp;gt; SRI &amp;gt; Aerobic and mean basal-soil respiration had SRI &amp;gt; IL &amp;gt; OIL &amp;gt; Aerobic. Soil labile carbon pools and heterotrophic populations were higher in OIL and dehydrogenase activity was higher in SRI. Microbial biomass carbon, readily mineralisable carbon, dehydrogenase activity and the heterotroph population showed positive correlations with RhR. Hence, regulation of RhR is crucial and can be achieved through rhizosphere modifications linked with labile carbon pools and soil enzymatic activities by plant physiological modification or through soil carbon stabilisation.

Evaluation of anaerobic germinability in various rice subpopulations: identifying genotypes suitable for direct-seeded rice cultivation

Anaerobic conditions in waterlogged soil lead to low germination rates, which significantly reduce crop yields. Good seed germination is prerequisite for direct-seeded cultivation of rice to obtain optimal yields not only in irrigated lowland but most importantly in rain-fed and waterlogged areas where water supply could be more than needed. Due to the limited availability of rice genotypes suitable for anaerobic germination, there is an urgent need to select diverse rice germplasm with enhanced anaerobic germinability. In this study, we evaluated 185 rice accessions from six subpopulations for germination rate (AGR) and coleoptile length (ACL) under anaerobic conditions. The highest average AGR (60%) and longest average ACL (2.13 cm) were observed in tropical japonica (TRJ) and temperate japonica (TEJ) germplasm, respectively. Meanwhile, the highest proportion of accessions with “very long” ACL was in the TEJ subpopulation, whereas those with the “highest” AGR were in the aus subpopulation based on our criteria. We selected seven strong accessions for anaerobic germinability (AG) based on AGR and ACL and analyzed the relative expression patterns of four AG-related genes in strong and weak accessions via qRT-PCR. In general, proton pyrophosphatase locus (OVP3) was expressed at the highest levels in strong accessions, whereas the expression level of rice ethylene response element binding protein locus (EREBP1) did not significantly differ among accessions under normal and anaerobic conditions. The relative expression results of rice alpha amylase locus (RAmy3D) and OVP3 showed distinct patterns and divided all strong accessions into two groups, suggesting that major genes involved in AG may vary depending on the germplasm. These findings could be helpful for breeders and lay the foundation for further genetic analysis.

Potensi Pasang Surut Lahan Rawa untuk Pengembangan Irigasi di Kabupaten Merauke Menggunakan Pemodelan Hidrodinamika 1D2D

Merauke Regency has three major rivers i.e Bian River, Kumbe River and Maro River (BIKUMA), the three rivers have large horizontal tidal potential. To know the potential of tides in the development of lowland irrigation in Merauke Regency needs to be studied. This study is supported by hydrometry and hydraulic surveys which has been conducted during the dry season during at spring tide and neap tide simultaneously for all three rivers. The survey included measuring river geometry activities with a range of 5 Km, river hydrometry measurements (observation of water fluctuations with proportional distances for model calibration and upstream river velocity for discharge). Limitations of river upstream measurements are limited by the distance where the Bian River along 125 Km, the River Kumbe along 171 km, and the Maro River along 66 km from the estuary. Then, performed a Sobek 1D hydrodynamic modeling that describes the movement of water from upstream into downstream. From the results of modeling is known that the water entering from the sea to the Bikuma River is greater than the water out to sea. The potential for tides is 1.7 Billion m3. Furthermore, the simulation of Sobek 1D2D to obtain the extent of natural condition, the area that can be inundated is 123.609 ha. Utilization of tidal potential can be channeled to the development zone through an integrated lowland irrigation water management system so that water utilization can be optimal.

Biomass production of different grass species available at irrigated lowland of Dassench Woreda in South Western Ethiopia

On farm adaptability test of different grass species was conducted on pastoral area of Keelewe peasant association in Dassench Woreda of South Omo Zone in 2016 under irrigated condition with the objective to identify high biomass yielding grass species. The field experiment was laid out in a Randomized Complete Block Design with four replicates per tested species. The tested grass species were Chloris gayana, Cenchrus ciliaris and Panicum colaratum. The result indicated that there was a significant difference (p&gt;0.05) among the tested grass species. Panicum colaratum yields the highest (18.08 t/ha) than the Chloris gayana (15.21 t/ha) whereas, Cenchrus ciliaris had yielded the lowest dry matter yield (11.20t/ha) than Chloris gayana and Panicum colaratum. The Panicum colaratum was one with maximum dry matter yield being recommended for irrigated conditions in the study area. However, further testing is required on feeding value, dry matter yield under different fertilizer dose, stem height, leaf to stem ratio, irrigation requirements and chemical composition of tested grass species.Bang. J. Anim. Sci. 2017. 46 (3): 188-191

Producer farmer’s sovereignty in dry land and swamps areas

Farmers could perform their farming if they have sovereignty on their farming production inputs and marketing. Suboptimal land, such as dry land and swamps areas have good prospect if applying appropriate technologies. A research in 2015, on status of farmers’ sovereignty, had been conducted in Piani and North Candi Laras Subdistricts, Tapin District, South Borneo Province, representing swamp land and dry land respectively. Data and information were obtained through interviewing related agencies at provincial and district levels and 30 units of farmer’s households. The primary and secondary data were analyzed descriptively. The research results showed that farmers in swamps and dry land were categorized as large farmers and had sovereignty over the land and production. Water shortage and excessive in both land types could be overcome by giving access on appropriate technology such as programs making farmers improve their farming techniques and providing levees. In addition, land certification program, farming expansion and constructing new irrigated lowland were also some efforts to improve farmers’ sovereignty. It was crucial to identify and improve farmer’s sovereignty indicators through research in larger sites and samples.

Standardization of alternate wetting and drying (AWD) method of water management in low land rice (Oryza sativa (L.))

Alternate wettting and drying (AWD) systems save water compared with continuoussubmergence (CS) irrigation. However, the reported effect on yield varies widely and detailedcharacterizations of the hydrological conditions of AWD experiments are often lacking so thatgeneralizations are difficult to make. We compared the effects of AWD and CS on crop andwater productivity in rice in the field experimentations in India. The experiment was conductedin irrigated lowlands and followed AWD practices by using field water tube. Crop and waterproductivity was significantly differed between AWD and CS of irrigation. The average grainyield was 5.8–7.4 t ha-1 with AWD irrigation methods and 7.5–7.6 t ha-1 with CS. The pooledvalues of irrigation water applied, effective rainfall and seasonal volume of water input variedfrom 1390, 216 and 1646 mm, respectively under CS and 708 to 1142 mm, 238 to 300 mm and1048 to 1420 mm, respectively under AWD irrigation regimes. Irrigation water applied in AWDirrigation regimes amounted to 50.9 to 82.1% of CS (1390 mm), averaged over two seasons, thecrop in different AWD irrigation regimes used water 63.6 to 86.2% of the CS (1646 mm)suggesting that the AWD practice enabled water saving of 13.8 to 36.4% in different treatments.Therefore, in view of considerable water saving (26.6 to 35.0%) and higher water productivitythe AWD method of water management is the best practice to meet the cope of water scarcity inlowland rice production.

A LiDAR-based flood modelling approach for mapping rice cultivation areas in Apalit, Pampanga

Majority of rice cultivation areas in the Philippines are susceptible to excessive flooding owing to intense rainfall events. The study introduces the use of fine scale flood inundation modelling to map cultivation areas in Apalit, a rice-producing municipality located in the province of Pampanga in the Philippines. The study used a LiDAR-based digital elevation model (DEM), river discharge and rainfall data to generate flood inundation maps using LISFLOOD-FP. By applying spatial analysis, rice cultivation zone maps were derived and four cultivation zones are proposed. In areas where both depth and duration exceed threshold values set in this study, varieties tolerant to stagnant flooding and submergence are highly recommended in Zone 1, where flood conditions are least favorable for any existing traditional lowland irrigation varieties. The study emphasizes that a decline in yield is likely as increasing flood extents and longer submergence periods may cause cultivation areas for traditional irrigated lowland varieties to decrease over time. This decrease in yield may be prevented by using varieties most suitable to the flooding conditions as prescribed in the rice zone classification. The method introduced in this study could facilitate appropriate rice cultivation in flood-prone areas.

Simulating the Impact of Nitrogen Management on Rice Yield and Nitrogen Uptake in Irrigated Lowland by ORYZA2000 Model

ABSTRACTThis paper considers the implications of ORYZA2000 model in simulating physiological traits of rice at different nitrogen concentrations. The experiment was conducted over the course of the growing season in 2012 and 2013 in Rice Research Institute, Deputy of Mazandaran, Iran. The variety used was Shiroudi as a high yielding variety. The considered factors were the amount of nitrogen at four levels (40, 80, 120, 160 kg N ha−1 and control) and nitrogen splitting in four levels. We compared simulated and measured grain yield, biomass, grain nitrogen, total plant nitrogen uptake, and leaf area index (LAI) by Student’s t-test of means and by absolute and normalized root mean square errors (RMSE). Results showed that grain yield was simulated with an RMSE of 411–423 kg ha−1 and a normalized RMSE of 6%. RMSE was 671–910 kg ha−1 for biomass on harvesting date. RMSE were 7–11 for grain nitrogen, and 10–13 for total plant nitrogen uptake. LAI was simulated with a normalized RMSE of 17–23%. Generally the model simulated LAI, an exceeded measured value for different nitrogen treatments. The most obvious finding that emerged from this study was that ORYZA2000 model can be applied as a supportive research tool for selecting the most appropriate strategies for rice yield improvement at various nitrogen fertilization concentrations.

On-farm rice yield and its association with biophysical factors in sub-Saharan Africa

Abstract Although increase in rice (Oryza spp.) production is a common objective for rice-producing countries in sub-Saharan Africa (SSA), basic information on yield and its variation at farm level is lacking. Field surveys were conducted in irrigated lowland (IL), rainfed lowland (RL), and rainfed upland (RU) rice production systems in 19 SSA countries in the 2012–2014 wet seasons. Mean yield varied widely across sites: 2.2–5.8 t/ha, 1.1–5.2 t/ha, and 1.0–2.5 t/ha in IL, RL, and RU, respectively. Rice yield levels differed between the agro-ecological zones (AEZs) with the highest yield in the semi-arid zone in IL, and in the highlands zone for RL and RU. Cluster analysis identified four groups using mean yields, coefficient of variation, and skewness of yield distribution of 42 site–production system combinations. Grouping was related to production system, AEZ, and field water condition. A high-yielding group with 5.3 t/ha mean yield and negative skewness had only four site–production system combinations. Other groups had mean yields from 1.6 to 3.5 t/ha with positive skewness. In these groups, research and development priority for lifting rice yield could be given to low-yielding IL and RL sites with large yield gaps. Raising rice yield in the humid zone irrespective of the production systems and RU across AEZs remain major challenges. Further assessment of the impact of farmers’ agricultural practices on yield variation is warranted to identify potential interventions to realize further yield enhancement.