Evaluation of biofertilizers in irrigated rice: effects on grain yield at different fertilizer rates

Biofertilizers are becoming increasingly popular in many countries and for many crops, but very few studies on their effect on grain yield have been conducted in rice. Therefore, we evaluated three different biofertilizers (based on Azospirillum, Trichoderma, or unidentified rhizobacteria) in the Philippines during four cropping seasons between 2009 and 2011, using four different fertilizer rates (100% of the recommended rate [RR], 50% RR, 25% RR, and no fertilizer as Control). The experiments were conducted under fully irrigated conditions in a typical lowland rice environment. Significant yield increases due to biofertilizer use were observed in all experimental seasons with the exception of the 2008/09 DS. However, the effect on rice grain yield varied between biofertilizers, seasons, and fertilizer treatments. In relative terms, the seasonal yield increase across fertilizer treatments was between 5% and 18% for the best biofertilizer (Azospirillum-based), but went up to 24% in individual treatments. Absolute grain yield increases due to biofertilizer were usually below 0.5 t·ha−1, corresponding to an estimated additional N uptake of less than 7.5 kg N ha−1. The biofertilizer effect on yield did not significantly interact with the inorganic fertilizer rate used but the best effects on grain yield were achieved at low to medium fertilizer rates. Nevertheless, positive effects of the biofertilizers even occurred at grain yields up to 5 t·ha−1. However, the trends in our results seem to indicate that biofertilizers might be most helpful in rainfed environments with limited inorganic fertilizer input. However, for use in these target environments, biofertilizers need to be evaluated under conditions with abiotic stresses typical of such systems such as drought, soil acidity, or low soil fertility.Niño Paul Meynard Banayo, Pompe C. Sta. Cruz, Edna A. Aguila, Rodrigo B. Badayos and Stephan M. Haefel

Productivity of sodic soils can be enhanced through the use of salt tolerant rice varieties and proper agronomic practices

AbstractRegaining the agricultural potential of sodic soils in the Indo-Gangetic plains necessitates the development of suitable salt tolerant rice varieties to provide an entry for other affordable agronomic and soil manipulation measures. Thus selection of high yielding rice varieties across a range of sodic soils is central. Evaluation of breeding lines through on-station and on-farm farmers’ participatory varietal selection (FPVS) resulted in the identification of a short duration (110–115 days), high yielding and disease resistant salt-tolerant rice genotype ‘CSR-89IR-8’, which was later released as ‘CSR43’ in 2011. Several agronomic traits coupled with good grain quality and market value contributed to commercialization and quick adoption of this variety in the sodic areas of the Indo-Gangetic plains of eastern India. Management practices required for rice production in salt affected soils are evidently different from those in normal soils and practices for a short duration salt tolerant variety differ from those for medium to long duration varieties. Experiments were conducted at the Indian Council of Agricultural Research-Central Soil Salinity Research Institute (ICAR-CSSRI), Regional Research Station, Lucknow, Uttar Pradesh, India during 2011 and 2013 wet seasons, to test the hypothesis that combining matching management practices (Mmp) with an improved genotype would enhance productivity and profitability of rice in sodic soils. Mmp were developed on-station by optimizing existing best management practices (Bmp) recommended for the region to match the requirements of CSR43. The results revealed that transplanting 4 seedlings hill−1 at a spacing of 15×20cm produced significantly higher yield over other treatments. The highest additional net gain was US$3.3 at 90kgha−1N, and the lowest was US$ 0.4 at 150kgha−1N. Above 150kgha−1, the additional net gain became negative, indicating decreasing returns from additional N. Hence, 150kgNha−1 was considered the economic optimum N application rate for CSR43 in these sodic soils. Using 150–60–40–25kg N–P2O5–K2O–ZnSO4·7H2Oha−1 in farmers’ fields grown to CSR43 produced an average of 5.5tha−1 grain. The results of on-farm evaluation trials of CSR43 showed that matching management practices (Mmp) increased yield by 8% over existing best management practices (Bmp) recommended by ICAR-CSSRI for sodic soils and by 16% over framers’ management practices; however, combining Mmp with CSR43 resulted in 35% higher yields over farmers’ current varieties and management. This approach of combining cost effective crop and nutrient management options and a salt-tolerant variety can maximize the productivity and profitability of sodic soils in the alluvial Indo-Gangetic plains and in neighboring salt-affected areas of the Ganges mega delta in South Asia

Response of salt-tolerant rice varieties to biocompost application in sodic soil of Eastern Uttar Pradesh

Sodic soils have immense productivity potential, if managed through proper technology interventions. Biocom-post is prepared by composting pressmud (a sugar industry byproduct) received from cane juice filtration and spent wash received from distilleries through microbial aerobic decomposition and can be used to reclaim sodic soils. Field experiments were conducted during the wet season of 2011 and 2012 to study the effect of incorpora-tion of biocompost in sodic soil with four treatments: T1—Control, T2—Biocompost at 2 t ha⁻¹, T3—Biocompost at 4 t ha⁻¹ and T4—Biocompost at 6 t ha⁻¹. The two promising salt tolerant rice varieties preferred by farmers, Narendra usar 3 and NDR 359 were used as test crops, which can produce yields ranging between 2 - 4 t ha⁻¹ in soil having a pH range of 9.2 to 10.5. Among the different doses of biocompost tested, application of biocompost at 6 t ha⁻¹ registered highest yields, enabled by a higher biomass, ear bearing tiller (EBT), and grain fertility in both varieties. Narendra usar 3 was more responsive to treatments even at lower doses of biocompost than NDR 359, but NDR 359 yielded slightly higher than Narendra usar 3 in all treatments. Soil health was also improved evidently on better fertility and low soil pH and EC at harvest. Thus, biocompost can be considered as a com-mercially viable, environmentally acceptable and practically enforceable option for improving the crop produc-tivity and soil fertility status.Akhtar H. Khan, Ashok K. Singh, Mubeen, Sudhanshu Singh, Najam W. Zaidi, Uma S. Singh, Stephan M. Haefel

Climate change and unfavorable rice environments: overview of approaches to assess trends and future projections

The likely impacts of climate change on rice-based agroecosystems in Asia are uncertain, especially for rainfed rice systems in theunfavorable environments that are vulnerable to precipitation changes. Regional impacts of climate change are typically assessedquantitatively through spatially downscaling a global circulation model (GCM), but this approach is inherently biased through the GCMselected, which is typically not more than one. In this paper, we pursue a different approach that is based on an ensemble analysisof several GCMs. In the first section, the ensemble analysis is illustrated by using two rainfed rice environments (in eastern India andBangladesh) as examples. Although the different GCMs showed a similar overall trend of declining precipitation, major discrepancieshave occurred in seasonal aspects of climate change. The spatial downscaling of predicted changes in precipitation projected thatthe changes are varying throughout the months and regions, probably further increasing the severity and the areas already plaguedby floods and droughts. The second section of the paper assesses the potential and constraints of seasonal forecasting as a meansto alleviate losses in rice production. Drought is a major production constraint in rainfed rice, so that forecasts on drought occurrencecan be used to alleviate losses. In a broader sense, short-term and long-term climate projections could be a key for achieving rising productivity in unfavorable rice environments.Kay Sumfleth and Stephan M. Haefel

Soil quality in rice-based rainfed lowlands of Asia: characterization and distribution

Organized jointly by the International Rice Research Institute (IRRI) and Indian Council of Agricultural Research (ICAR), the theme of this congress is "Science, technology, and trade for peace and prosperity". It comprises four major events: the 26th International Rice Research Conference; the 2nd International Rice Commerce Conference; the 2nd International Rice Technology and Cultural Exhibition; and the 2nd International Ministers` Round Table Meeting.The rainfed lowland rice production system in Asia covers about 46 million hectares, which is almost 30% of the total rice area worldwide. Production in much of this system is hampered by drought, submergence, and multiple soil constraints. The Green Revolution largely bypassed these difficult environments and they continue to be characterized by low agricultural productivity and widespread poverty. More recently, there has been some success with technology development and adaptation. However, the potential and realized benefits from research and development efforts in the rainfed lowland ecosystem will continue to strongly depend on indigenous soil fertility and soil-related constraints. As a first step in our effort to better characterize soil and water resources in rice-based rainfed lowland systems at the regional and landscape level, we characterized the distribution and frequency of soil constraints in rainfed lowlands. Seven percent of rainfed rice is grown on problem soils such as acid-sulfate soils or saline soils. One-third of rainfed lowland rice is grown on relatively fertile soils, slightly less than one-third grows on soils with low indigenous soil fertility, and slightly more than one-third grows on soils with considerable soil constraints often combined with very low soil fertility. Rainfed lowland rice in Southeast Asia is much more likely to be on poor soils with various soil constraints than in South and East/Northeast Asia.S.M. Haefele and R.J. Hijman

Long-term fertility experiments for irrigated rice in the West African Sahel: agronomic results

Long-term fertility experiments (LTFEs) are a tool to investigate the sustainability of cropping systems. Several LTFEs for intensive irrigated rice cropping were established in Asia, but those are rare in Sub-Saharan Africa. Two such trials are presented, both located in the Sahel savanna vegetation zone in Senegal. The trials were established in 1991, contain six different fertilizer treatments and rice is growntwo times per year. Soil type at Ndiaye is a typical Orthithionic Gleysol and an EutricVertisol at Fanaye. Average grain yieldswithout fertilizer applicationwere 3.4 Mg/ha per season in Ndiaye and 2.9 Mg/ha per season in Fanaye. In 20 consecutive seasons best treatments at both sites and in both seasons yielded on average between 6.7 and 7.6 Mg/ha per crop. Yield components were influenced by cultivar, site, season and fertilizer treatment. The mineral composition of grains was homogenous between cultivars and similar to results from Asia, Australia and the USA. Significant differences among cultivars were found for the mineral composition of straw, especially for Si, Fe, Zn and K. Nitrogen, P and K fertilizer treatments increased themineral concentrations ofN, P,Mg, Ca,Mn and Cu.Highest yields in the LTFE indicate a not significant yield decline of -27 kg per season in Ndiaye and a significant increase in Fanaye (þ86 kg per season). The crop model ORYZAS simulated that potential yields declined by -50 kg per season in Ndiaye and increased by +16 kg per season in Fanaye (not significant). Simulated yield trends were not always mirrored by trends of average seasonal radiation, which is due to the influence of unfavorable temperature extremes on yield and yield simulations. It is concluded that observed yield trends can largely be explained by climatic influences. The agronomic analysis did not indicate a negative impact of intensive irrigated rice cropping on the soil resource base

A framework to improve fertilizer recommendations for irrigated rice in West Africa

A framework to optimize soil fertility management in irrigated rice, based on soil and climate variability, fertilizer and paddy prices and farmers' objectives is presented. The framework uses three models in succession. The dynamic ecophysiological ORYZAS model simulates potential rice yields under irrigation, based on weather conditions, cultivar choice and sowing date. This yield potential is used in the static FERRIZ model, together with site specific information on recovery efficiency of applied N, P and K, indigenous soil N, P and K supply, and maximum N, P and K accumulation and dilution in rice dry matter. Resulting outputs are required fertilizer doses to obtain different target yields depending on yield potential and soil nutrient supply. The framework allows sensitivity analysis and agro-economic evaluation of different fertilizer options. In a last step, the dynamic decision tool RIDEV is used to simulate optimal timing of different management actions such as fertilizer application, weeding, and harvest. Resulting integrated crop management recommendations ensure high resource use efficiency adapted to local socio-economic and bio-physical conditions. Provided necessary input data are available, this framework can be applied to field, perimeter or regional scale. The framework was applied to the Office du Niger in Mali, using field data of 58 farmers. In the wet season, fertilizer doses adjusted to three soil fertility classes out-performed current uniform recommendations only slightly, except on soils with very low K supply (10 cases). Only on these soils was application of K profitable. Profit-optimizing fertilizer doses had high costs and low value/cost ratios. Target yields close to potential yield increased farmers' risk. Adjusting fertilizer doses to the lower yield potential in the dry season reduced costs and risk without reducing profit, resulting in better value/cost ratios. New simple recommendations for both wet and dry seasons were formulated. (C) 2003 Elsevier Science Ltd. All rights reserved

Characteristics and management options for rice-maize systems in the Philippines

In the Philippines, maize (corn) is the second major cereal crop after rice. Around 0.12 million ha of maize are grown in rice-maize (R-M) systems, mostly situated in the lowlands, and the area of this system is growing fast. The objectives of this study were to describe the targeted cropping system, to test several management options that could help to optimize it and reduce the production risk, and to develop a simple nutrient balance as a sustainability indicator. For this, we conducted participatory onfarm trials in Pangasinan province, where about 33,600 ha of yellow maize are grown, mostly in R-M systems. Combined grain yields of the system reached 14 t/ha in the first year and 21 t/ha in the second year, depending on the treatment. Yield differences were mostly due to climate-induced stresses in the first year and very favorable conditions in the second year. Varietal choice in rice was an option to reduce production losses by selecting the variety according to average field-specific characteristics (drought-prone, favorable, flood-prone). Balanced fertilizer applications reduced stress-dependent rice yield losses considerably, and helped to maximize grain yield in the favorable season. The rice fertilizer treatment without any application caused lower yields in the subsequent maize crop but the effect was not significant. No effects of field topography on soil chara cteristics or on grain yields of rice or maize were detected. The nutrient balance indicated the considerable danger of soil nutrient mining in this cropping system, which could aggravate possible trends of declining soil organic matter concentrations in R-M systems that have been shown in previous studies. We concluded that a combination of adjusted management components can reduce production risk and optimize system productivity. To maintain system productivity, it seems most promising to combine different management elements, including balanced NPK fertilizer rates with limited PK mining, recycling of waste products from residue use on the farm as much as possible, and only limited removal of residues from the fields

Critical Limit of Extractable Phosphorous in a Gleysol for Rice Production in the Senegal River Valley of West Africa

Soil-test correlation and calibration, a useful tool for fertilizer recommendations, has been little used in West Africa. Soils from a long-term fertility experiment have been used to study the relationship between rice yields and soil extractable phosphorus (P) with Bray 1 and Olsen methods. The Cate and Nelson graphical method was used for critical limits of soil P determination. The critical limits of soil extractable P at 95% relative grain yield were 9 mg P for the Bray 1P and 17 mg P kg21 for Olsen P. The Olsen P was more correlated (r ¼ 0.63) with rice grain yields than Bray P (r ¼ 0.50), but a strong correlation (r ¼ 0.92) was also observed between the values of the two methods. Results indicate that at levels less than these critical levels of extractable P, P fertilizers should be applied to increase rice yields