Department of Crop Science
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Item Effect of temperature on the development of Orius albidipennis Reuter, a predator of the African legume flower thrips, Megalurothrips sjostedti Trybom(2002) Gitonga, L. M.; Löhr, B.; Overholt, W. A.; Magambo, J. K.; Mueke, J. M.The effects of temperature on the development of Orius albidipennis (Reuter) (Hemiptera: Anthocoridae), reared on its prey, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), were studied in the laboratory. Nymphal mortality was 87, 48 and 38 % at 20, 25 and 30 °C, respectively. With the exception of first-instar nymphs, percentage mortality was lowest at 25 °C. Pre-oviposition period and longevity decreased with an increase in temperature. Mean daily and total fecundity were 2.1 and 76.4 respectively at 25 °C. The mean developmental period from oviposition to adult eclosion was 27.7, 14.1 and 10.9 days at 20, 25 and 30 °C respectively. There was a linear relationship between temperature and developmental rate (1 /day) of O. albidipennis. Lower thermal thresholds were 13.8, 13.5, 12.7, 15.0, 13.8 and 12.5 °C for eggs and nymphal stages 1 to 5, respectively, with the corresponding average degree-day requirement of 46.9, 42.6, 33.3, 29.2, 26.1 and 51.4 days, respectively. The implications of these results for biological control of thrips are discussed.Item The Critical Onion Growth Stages For Selective Protection From Thrips Tabaci Lindeman (Thysanoptera:Thripidae) Infestation(Kenya Agricultural Research Institute, Nairobi (Kenya), 2006-01) Waiganjo, M. M.; Sithanantham, S.; Mueke, J. M.; Gitonga, L. M.Field trials were conducted during 2000-2001 at KARIandrsquo;s Mwea-Tebere and Kiboko farms to establish the effect of onion thrips, Thrips tabaci Lindeman on onion bulb yields and to identify the critical onion growth stage for selective protection from the pest infestation. Yield reductions of 59 and 27% were recorded in the first and second crops respectively at Mwea-Tebere, but no significant yield reductions were observed in a third crop grown at Kiboko with low thrips infestation. A significant onion yield response to thrips infestation was observed during the 2nd month after transplanting (bulb-formation) and 3rd month after transplanting (bulb-enlargement), but no significant response was observed during the 1st month (pre-bulbing) and 4th month (maturation stage). Onion protection during bulb-formation and enlargement stages only, resulted in higher marginal returns than full season pesticide application. The studies suggest that control recommendations for onion could be refined to optimize need-based protection.Item Antimicrobial acitivity of extracts from Tephrosia vogelii Hook F.(2007-01-29) Wanga, B. N.; Akenga, T.; Imbuga, M.; Gitonga, L .; Olubayo, F.; Namungu, P.The dichloromethane extracts of the root and leaf of Tephrosia vogelii Hook F. (Family: Papilionaceae) grown in Kenya, were subjected to antimicrobial assays against Staphylococcus aureus, Escherichia coli and Fusarium phoseolida. The minimum inhibition concentrations (MIC) ranged between 0.25 to 6.4 μg/ml for all the microorganisms tested. The crude root and leaf extracts were also toxic to the brine shrimps, organisms used as indicators of toxicity (LC50: 0.960; 0.958 μg/ml, respectively). Chromatographic separation led to the identification of (6aß, 12aß, 5'ß)-6a, 12a, 4',5'-tetra hydro-2,3-dimethoxy 5'-ß- isopropenyl–furano (3',2': 8,9)-6H-rotoxen-12-one, (rotenone) in 9.75% yield, (roots), and 11.75% (leaves). Characterisation was achieved by use of spectroscopic techniques and comparison with rotenone standard and literature data. Novel HPLC conditions for purification of rotenoids were established. The MIC of rotenone against the tested microbes was found to be 5.2 and 1.0 μg/ml for Staphylococcus aureus and Escherichia coli respectively, while the LC50 against the brine shrimps was found to be 3.20 μg/ml. The findings indicate that the extracts of T. vogelii contain metabolites that have antimicrobial activity comparable to other medicinal plants.Item Scope for genetic enhancement of the parasitisation potential of four native strains of Trichogrammatoidea sp. nr. lutea Girault (Hymenoptera: Trichogrammatidae(Taylor & Francis, 2007-09) Baya, Joseph M.; Sithanantham, S.; Gitonga, Linus; Osir, EllieIn response to emerging interest in commercial mass production of Trichogramma for Helicoverpa armigera biocontrol in eastern Africa, laboratory experiments were undertaken to assess the scope for genetic enhancement of the parasitisation potential of native strains of the local common trichogrammatid species, Trichogrammatoidea sp. nr. lutea. Four promising strains (ex-Kilifi – Kilifi District, ex-Kwa Chai – Kibwezi District, ex-Rarieda – Bondo District and ex-Ebuhayi, Kakamega District) were tested for cross-mating in reciprocal combinations with focus on fecundity and progeny female ratio. While all the crosses resulted in F1 progeny of both sexes, significant differences were observed between homogamic and reciprocal heterogamic crosses in fecundity, progeny production, proportion of female progeny and adult longevity. Among all the crosses, the cross between ex-Rarieda strain females and ex-Kilifi strain males resulted in progeny that was significantly superior in fecundity and progeny female ratio. Conversely, Kilifi strain females crossed to males from ex-Rarieda strain gave rise to progeny with relatively low fecundity and female ratio. There were significant differences between homogamic crosses and most reciprocal heterogamic crosses in the major biological attributes. Genotypic and phenotypic variance-covariance matrices generated for six life-history traits showed high positive correlations for most traits in both inbred (P<0.05) and reciprocal heterogamic crosses (P<0.05 and P<0.001). Fecundity and number of female offspring were the most important factors in the heterogamic crosses. The results confirmed the scope for genetic enhancement through inter-strain crossing for improving the field impact potential of T. sp. nr. lutea being targeted for commercial mass production.Item Effect of soil PH on postharvest pathological deterioration of sweet potato storage roots(African Journal of Horticultural Sciences, 2008) Kihurani, A.W.; Narla, N.D.; Shibairo, S.; Imungi, J.; Carey, E.Sweet potato (Ipomoea batatas (L.) Lam.) is the world’s seventh most important food crop but its potential to contribute to food security and income generation is limited in tropical developing countries by its short shelf-life. Environmental and cultural stresses during growth are known to directly or indirectly predispose sweet potato storage roots to postharvest microbial infection. Research was conducted to determine the effect of soil pH on postharvest deterioration of sweet potato roots using two sweet potato cultivars, Yanshu 1 (CIP 440024) and KSP 20 (CIP 440170), and three soil pH levels, 4.6, 5.8 and 6.1 arranged in randomized complete block design with four replications. Preharvest experiments were conducted in a greenhouse followed by postharvest evaluations in the laboratory at the National Agricultural Research Laboratories (NARL), Nairobi. Nine-mm circular agar plugs, removed from the edge of actively growing two-day old culture of two postharvest pathogens of sweet potato, Rhizopus oryzae and Botryodiplodia theobromae, were used to inoculate the sweet potato roots. Pathological deterioration (PD) was estimated by measuring the diameter and depth of the developing internal lesion (extent of tissue degradation) on the storage roots, 24 hours after inoculation. Results showed that postharvest PD of the storage roots was not significantly (P>0.05) influenced by growing sweet potato in soil at the different pH levels. Growing sweet potato in soil at pH levels within the range for normal plant growth is unlikely to affect postharvest deterioration of the storage roots.Item Evaluation of feed for rearing corcyracephalonica and optimisation of host and parasitoid ages for mass-production of trichogramatid parasitoids(2008) Migiro, L. N.; Gitonga, L. M.; Sithanantham, S.Item SUSCEPTIBLE ONION GROWTH STAGES FOR SELECTIVE AND ECONOMIC PROTECTION FROM ONION THRIPS INFESTATION(Karatina University, 2008-03) Waiganjo, M.M; Mueke, J.M.; Gitonga, LinusThe growth of the bulb onion is subject to significant stress and yield reduction caused by sap feeding onion thrips. In Kenya, the general control recommendation is to spray the crop with insecticides as soon as the pest appears and to continue thereafter, throughout the crop season. The practice is expensive and environmentally hazardous. Two field trials were conducted at the Kenya Agricultural Research Institute (KARI) Mwea-Tebere farm to identify the growth stages most susceptible to onion thrips infestation that would provide the highest economic benefits to the onion grower by managing thrips, with the aim of promoting need-based onion pesticide application. The trial design was randomized complete blocks of 16 treatments replicated three times. The treatments constituted insecticide treatments at different onion growth stages and frequencies. Thrips density/plant was estimated weekly through a destructive cutting and bagging method. Yield gains due to the application of the protection regimes were calculated and the marginal returns estimated as the income of yield gain divided by the cost of the control option. Thrips infestation was significantly (p=0.05) higher in the unprotected plots than all the protected plots in the first and second trial and resulted in significant yield losses of 59 and 29%, respectively. A significant onion yield response to thrips infestation was observed during the 2nd month (bulb-formation) and 3rd month (bulb-enlargement) after transplanting, but no significant response was observed in the 1st month (pre-bulbing) and 4th month (maturation) respectively. Onion protection only during the bulb-formation stage resulted in higher marginal returns than full season pesticide application. The studies suggested that control recommendations for onion thrips could be refined to optimize selective pesticide use in Kenya.Item Preventive control alternatives to routine foliar spray against Thrips tabaci in onions(2008-10) Waiganjo, M.; Sithanantham, S.; Gitonga, Linus; Mueke, J. M.-Item Seasonality and potential of Ceranisus menes for control of thrips on French beans(Sida, 2008-10-22)-Item HOST-PLANT ACCEPTANCE, FECUNDITY AND LONGEVITY OF Tetranychus evansi (Acari: Tetranychidae) ON SELECTED TOMATO ACCESSIONS(2009) Murungi, L. K.; Knapp, M.; Masinde, P. W; Onyambu, G.; Gitonga, L.; Agong, S. G.Seventomato (Lycopersicon sp.) accessions wereevaluated for their resistance to thetomato red spider mite, Tetranychus evansi Baker and Pritchard, in the laboratory. Data recorded was: (i) trichome density and (ii) fecundity and longevity. Whole potted intact tomato plants were used for the olfactometer bioassays, while leaf disk sections were used for the glass bridge bioassays. There was a significant (P<0.05) negative correlation between fecundity and longevity with the density of trichome types I and IV. Significantly more females chose the direction with ‘Money Maker’ (susceptible accession) when compared to other accessions. Thus, trichome density and plant-emitted volatiles seem to play an important role in host- plant selection of spider mites.Item Organic and Mineral Input Management to Enhance Crop Productivity in Central Kenya.(2009-09) Chivenge, P.; Vanlauwe, B.; Gentile, R.; Wangechi, H.; Mugendi, D.; van Kessel, C.; Six, J.Organic resources (ORs) are important nutrient inputs in tropical agriculture. Combined with mineral fertilizers, they form the backbone of integrated soil fertility management. This study was conducted to determine the medium- to long-term influence of OR quality and quantity on maize productivity and to evaluate the occurrence of additive benefits in terms of extra grain yield produced by the combined application of ORs and N fertilizers. Farmyard manure, high quality Mexican sunflower [Tithonia diversifolia (Hemsl.) A. Gray], intermediate quality calliandra (Calliandra calothyrsus Meisn.) and maize (Zea mays L.), and low quality silky-oak (Grevillea robusta A. Cunn. ex R. Br.) sawdust were incorporated into the soil at equivalent rates of 1.2 and 4 Mg C ha−1 yr−1 in Embu (clayey) and Machanga (sandy soil), together with a control to which no OR was added. All plots were split, with one half receiving 120 kg N ha−1 season−1 as CaNH4NO3. The ORs, except sawdust and maize, improved maize grain yields compared with the control at both sites. Greatest mean maize yields (i.e., 4.9 and 2.3 Mg ha−1 season−1, in Embu and Machanga, respectively) over 10 seasons were observed with the high rate of Mexican sunflower, but was not significantly different from calliandra and manure. Generally, maize yields were greater with higher than lower OR rates, except for maize and sawdust. Although N fertilizer additions to the ORs improved grain yields in Embu, the increase was marginal; resulting in negative interactive effects of applying ORs with N fertilizers, especially with high-N ORs. Thus high-N ORs should not be applied in combination with N fertilizers, especially at such high fertilizer N rates.Item Do Mixed-Species Legume Fallows Provide Long-Term Maize Yield Benefit Compared with Monoculture Legume Fallows?(Wiley, 2009-11-01) Ndufa, James K.; Gathumbi, Stanley M.; Kamiri, Hellen W.; Giller, Ken E.; Cadisch, GeorgThe deliberate planting of fast-growing N2–fixing legume monoculture species in rotation with cereal crops can be an important source of N for soil fertility replenishment. We hypothesized that mixed-species fallows have a higher potential of giving long-term residual benefits in terms of biomass, nutrients, and quality of residuals leading to long-term nutrient supply to postfallow maize (Zea mays L.) crops. To test these hypotheses, two experiments were established in farmers' fields on very fine Kandiudalfic Eutrudox soils with monoculture and mixed-species fallows. Treatments included: sesbania [Sesbania sesban (L.) Merr.], crotalaria (Crotalaria grahamiana Wight and Arn.), pigeonpea [Cajanus cajan (L.) Millsp.], siratro [Macroptilium atropurpureum (DC.) Urb.], and calliandra (Calliandra calothyrsus Meissn.) as monoculture-species fallow and mixture fallows of sesbania + crotalaria, sesbania + pigeonpea, sesbania + siratro, or sesbania + calliandra compared with continuous maize cropping with or without N fertilizer, and natural weed fallow. Total aboveground biomass ranged from 4.1 to 20.5 Mg ha−1 for monoculture and 7.8 to 23.3 Mg ha−1 for mixed-species fallows. Recyclable fallow biomass N ranged from 70 to 313 kg ha−1 and there was a positive interaction in some mixtures leading to increased N accumulation. Postfallow maize yields for fallows over five cropping seasons were 161–272% or 61–103% higher when compared with continuous maize without or with N fertilizer, respectively. Long-term postfallow effects on maize yield were linearly related to the amount of recycled fallow N yield. Thus, choice of fallow species to mix should be primarily driven by a better risk management strategy and an increased basket of multiple products and services.Item Biological control agents of aphids (Homoptera: Aphididae) on potatoes (Solanum tuberosumL) in Kenya(2010) Machangi, J. M.; Gitonga, L. M.; Nderitu, J. H.; Maniania, N. K.; Kabira, J. N.A field survey was conducted in four major potato growing areas in Kenya (Kiambu, Nyandarua, Meru and Molo Districts) during January and February, 2008 (short rains crop) and June 2008 (long rains crop) to determine the occurrence of predators, parasitoids and pathogens of the aphids Myzus persicae Sulzer and Aphis gossypii Glover in potato crops. In each of the four areas, 30 potato farms distributed in different parts of the survey area were selected at random for the surveys. Insects collected were brought to the laboratories at the International Centre of insect physiology and Ecology (icipe), Nairobi, for identification and fungal infection. For isolation of fungal pathogens, dead aphids were transferred on moist filter paper placed on sterile Petri dishes to allow the growth of the fungus on the surface of the cadaver, after which fungus was transferred on artificial media for isolation. Four aphid species, M. persicae, A. gossypii, Macrosiphum euphorbiae Thomas and Aulacorthum solani Kaltenbach were identified in all the four survey areas. Sixteen predator species of the aphids were identified. The most prevalent were the ladybeetles Harmonia axyridis (Pallas) and Hippodamnia convergens Guérin-Méneville (Coleoptera: Coccinellidae), followed by the minute pirate bugs, Orius spp. (Heteroptera: Anthocoridae) and the aphid eating gall midge Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae). Three hymenopteran parasitoid species (Braconids followed by Chalcids then the Ichneumonids) and four fungal pathogen species, Beauveria bassiana Balsamo (Ascomycota: Hypocreales), followed by Verticillium lecanii Zimmermann (Hypocreales: Incertae sedis), Metarhizium anisopliae (Metsch.) Sorokin (Deuteromycotina: Hyphomycetes) then Pandora neoaphidis (Remaudière &Hennebert) Humber (Zygomycetes:Entomophthorales) were identified in all four areas of the field survey.Item Constraints to On-Farm Maize (Zea mays L.) Seed Production in Western Kenya: Plant Growth and Yield(ISRN Agronomy, 2012) Wambugu, P.W.; Mathenge, P.W.; Auma, E.O.; VanRheenen, H.A.Studies have shown that that about 85% of maize farmers in Western Kenya plant local varieties with about 80% using own farm-saved seeds. The production system is characterized by late harvesting, heavy striga infestation, use of local varieties, and low-soil fertility. The objective of this study was to test an on-farm seed production system which would help improve yield and quality of farm saved seeds. The trials were set up in a factorial design fitted as random complete block design. There were 3 factors each at 2 levels: time of harvest, variety choice, and fertilizer application. Fertilizer application led to an 88% increase in yield, 54% increase in number of seeds per cob, and 14% increase in 100-seed weight. Fertilizer application also led to an increase in seed vigour and viability. Yield differences between the 2 varieties were not significant. The correlation between 100-seed weight and seed vigour was significant showing that heavy seeds were more vigorous. Nitrogen application was therefore recommended for increasing yields and for producing vigorous seeds but should be done with caution to avoid lodging as witnessed. This study also noted that farmers are rational and their decisions are usually based on strong economic considerations.Item An Assessment Of The Physiological Quality Of Sorghum (Sorghum Bicolor L Moench) Seeds Planted By Farmers In Bomet District Of Kenya(African Journal of Food, Agriculture, Nutrition and Development, 2012-08) Ochieng, L.A; Mathenge, P.W.; Muasya, R.Sorghum (Sorghum bicolor L. Moench) is an important crop that enhances food security in a region. As a food crop, sorghum is nutritious, containing starch (75-79%) as the major component, followed by protein (6.0-16.1%) and oil (2.1-5.0%). Despite the crop’s versatility, it is regrettable that sorghum yields are still fairly low in Bomet District of Kenya. One of the constraints associated with low yields is the accessibility to good quality seeds by farmers. It was assumed in this study that use of low quality seed was among the factors that could be significantly affecting the low production of sorghum in the district. This study focused on the physiological quality of seed which refers to the germination capacity, viability, characteristics related to dormancy and vigour of the seed. A total of 100 farmers were interviewed and 80 seed samples were obtained from 80 farmers. The seeds were subjected to viability and vigour quality tests. These tests included germination (as a viability test); mean germination time and electrical conductivity tests (as vigour tests). About 29% of the seed samples taken for germination test were below the laboratory standards as stipulated in the seeds and Plant Varieties Act (CAP 326). Critical electrical conductivity values and critical mean germination time values were derived during the study. In accordance with the critical values arrived at in this study, 27.5% of the seed samples showed relatively high electrical conductivity readings and 36.3% of the seed samples showed longer mean germination time. However, 11.3% of the seed samples showed high germination percentages of above 90%. Since about 29% of farmers seeds were of bad physiological quality, it was concluded that this proportion of seed can result in poor yields and hence cause food insecurity to the people of the society, and thus requires further consideration for improvement. This study recommends that further research be conducted on the genetic, physical and sanitary quality aspects of seed planted by farmers in Bomet District so that a definite conclusive statement about the quality of seed planted by farmers in the District can be made.Item Evaluation of biological attributes of a native egg parasitoid, Trichogrammatoidea sp. nr. lutea (girault), kenyan accessions(2012-09-10) Lagat, Zipporah Osiemo; Gitonga, Linus; Muya, Shadrack Muvui; Ng ' Endo, RossaObjective: This study was carried out to evaluate the biological attributes that is, parasitism, adult progeny production, and sex ratio of 21 strains of a native egg parasitoid Trichogrammatoidea sp. nr. lutea Girault (Hymenoptera: Trichogrammatidae) collected from Plutella xylostella Linnaus (Lepidoptera: Yponomeutidae) in coastal Kenya, reared on Corcyra cephalonica Sainton (Lepidoptera: Pyralidae) in the laboratory. Methods:Atotal of 21 accessions of T.sp. nr. lutea were assembled from the Kenyan coast (Shimba hills and Muhaka sites). Preliminary experiments to select the best performers among the 21 strains, based on biological attributes such as adult longevity, parasitism, emergence, adult progeny produced and progeny sex ratio were conducted under laboratory conditions (temperature of 27±2°C and 65±10% RH). Results: There were significant differences (P<0.05) in all biological attributes studied among the strains. The overall mean adult longevity was 9.31 days. Parasitism, emergence and sex ratio per adult female were 20.2%, 75.56% and 37.77% respectively. The wasp age influenced all the attributes tested significantly (P<0.05) of T.sp. nr. lutea. Conclusion: Four accessions (SH-1 and 4, MK-1 and 3) were selected and recommended from this experiment based on adult longevity, parasitism, adult progeny produced and sex ratio for further evaluation. The results from this study will be useful for mass rearing purposes as well as for future field release programmesItem Article Navigation JOURNAL ARTICLE Evidence for Potential of Managing Some African Fruit Fly Species (Diptera: Tephritidae) Using the Mango Fruit Fly Host-Marking Pheromone(Entomological Society of America, 2012-12-01) Kachigamba, Donald L.; Ekesi, Sunday; Ndung'u, Mary W.; Gitonga, Linus M.; Teal, Peter E. A.; Torto, BaldwynWe investigated conspecific and heterospecific oviposition host discrimination among four economically important fruit fly pests of mango in Africa (Ceratitis capitata, Wiedemann; C. fasciventris, Bezzi; C. rosa, Karsch, and C. cosyra, Walker) with regard to host-marking behavior and fecal matter aqueous solutions. The objective of the study was to get insight into the potential of managing these pests using the host-marking technique. Observations were done on mango slices marked by the flies and treated with aqueous solutions of fecal matter of the flies, respectively. In both host-marking and fecal matter experiments, C. cosyra, which is the most destructive species of the four on mango, was exceptional. It only discriminated against hosts treated with its fecal matter but with lower sensitivity while C. capitata and C. fasciventris discriminated against hosts marked by it or treated with its fecal matter and with higher sensitivity. Our results provide evidence for potential of managing some of the major fruit fly species infesting mango in Africa using the host-marking pheromone of the mango fruit fly, C. cosyra.Item Effect of management and soil moisture regimes on wetland soils total carbon and nitrogen in Tanzania(Geophysical Research Abstracts, 2013) Kamiri, Hellen; Kreye, Christine; Becker, MathiasWetland soils play an important role as storage compartments for water, carbon and nutrients. These soils implies various conditions, depending on the water regimes that affect several important microbial and physical-chemical processes which in turn influence the transformation of organic and inorganic components of nitrogen, carbon, soil acidity and other nutrients. Particularly, soil carbon and nitrogen play an important role in determining the productivity of a soil whereas management practices could determine the rate and magnitude of nutrient turnover. A study was carried out in a floodplain wetland planted with rice in North-west Tanzania- East Africa to determine the effects of different management practices and soil water regimes on paddy soil organic carbon and nitrogen. Four management treatments were compared: (i) control (non weeded plots); (ii) weeded plots; (iii) N fertilized plots, and (iv) non-cropped (non weeded plots). Two soil moisture regimes included soil under field capacity (rainfed conditions) and continuous water logging compared side-by-side. Soil were sampled at the start and end of the rice cropping seasons from the two fields differentiated by moisture regimes during the wet season 2012. The soils differed in the total organic carbon and nitrogen between the treatments. Soil management including weeding and fertilization is seen to affect soil carbon and nitrogen regardless of the soil moisture conditions. Particularly, the padddy soils were higher in the total organic carbon under continuous water logged field. These findings are preliminary and a more complete understanding of the relationships between management and soil moisture on the temporal changes of soil properties is required before making informed decisions on future wetland soil carbon and nitrogen dynamics.Item Dynamics of agricultural use differentially affect soil properties and crop response in East African wetlands(Springer Science, 2013) Kamiri, Hellen; Kreye, Christine; Becker, MathiasAgricultural land use changes differen- tially affect soil fertility and crop production potential of wetlands. We studied East African wetlands with contrasting hydro-geological characteristics (high- and lowland floodplains and valley swamps). Land uses ranged from no use and grazing over crop production in flooded and drained fields to abandon- ment. We classified the dynamics of wetlands’ con- version into agricultural sites and assessed selected soil fertility attributes associated with land use changes, and their effect on the crop production potential in aerobic and anaerobic soils. A conversion of pristine wetlands, differing in soil physical and chemical attributes, into sites of production tended to negatively affect soil total C and N. Effects were stronger with soil drainage and in the coarse-textured soils of the lowland floodplain and the mid-hill valleys. Mineral P application in drained valleys significantly increased available soil P. Crop response followed these patterns with usually higher biomass accumulation and nutrient uptake in flooded than aerobic soils. Wetlands of fine soil texture in the highlands appeared more resilient than coarse-tex- tured soils, particularly when drained. Enhanced crop performance in flooded soils indicates the possibility for partial recovery of the production potential and the rehabilitation of some wetlands. Keywords Carbon Drainage Floodplain Inland valley Nitrogen Oryza glaberrima