SIMULATING RICE YIELDS UNDER CLIMATE CHANGE SCENARIOS USING THE CERES-RICE MODEL

The effects of climate change on rice production and yield cannot be overlooked in finding measures to increase production and yield. The CERES-Rice (Ver. 4.O) model was calibrated and evaluated for use in simulating rice yields under different climate change scenarios in Ghana using data from the Anum Valley Irrigation Project. Eighteen years of weather data (1989-2OO6) was used to run the model. The model was found to be sensitive to climatic parameters (temperature, CO2 concentration, solar radiation and rainfall) and had various effects on rice. Simulated rice yields were sensitive to weather years as there was 13% less yield of rice in 1999 compared with 2OO1. Increases or decreases of temperature by 4 °C from the maximum or minimum, decreased rice yields by 34% as compared to base scenario of 2OO6. Similar change in temperatures along with an increase in solar radiation by 1 MJ m-2 day-1, decreased rice yield by 32% compared to base scenario. On the other hand, the same changes in temperature from the maximum and minimum, together with an increase in CO2 concentration by 2O ppm from the standard CO2 concentration of 33O ppm, led to a reduction in rice yield of 33%. Simulations demonstrate that the effects of planting dates cannot be overlooked in finding measures to increase rice yield under climate change mitigations. The effects of climate change on rice yield of will depend on the actual patterns of change in rice growing areas. However, the negative impacts can be averted through appropriate measures such as changes in agronomic practices, development of more temperature tolerant rice varieties and effective training of farmers.Les effets du changement climatique sur la production et le rendement du riz ne peuvent être négligés lors de la prise des mesures pour accroître la production et le rendement. Le modèle Ceres-Rice (ver. 4.O) était calibré et évalué pour la simulation des rendements du riz sous différents scenarios de changement climatique au Ghana en utilisant des données fournies par le projet d’irrigation de la vallée d’Anum. Les données climatiques couvrant 18 ans (1989-2OO6) étaient utilisées dans ce modèle. Le modèle était trouvé sensible aux paramètres climatiques (température, concentration en CO2, radiation solaire et pluviométrie) et présentait des effets variés sur le riz. Les rendements simulés de riz étaient sensible aux années climatiques étant donné 13% de diminution du rendement du en 1999 en comparaison avec 2OO1. Des augmentations ou diminutions de la température de 4 oC du maximum ou minimum, avaient induit une diminution de 34% de rendements comparée au scenario de base en 2OO6. Des changements similaires de température avec un accroissement de la radiation solaire de 1 MJ m-2 jour-1, avait induit une diminution du rendement du riz de 32% en comparaison avec le scenario de base. D’autre part, les mêmes changements en température du maximum au minimum avec une augmentation de la concentration de CO2 de 2O ppm de la concentration standard de CO2 de 33O ppm, avait entrainé une réduction de rendement du riz de 33%. Les simulations démontrent que les effets des dates de plantation ne peuvent pas être négligés dans la recherche des mesures pour accroitre le rendement du riz dans la mitigation des effets de changement climatique. Les effets du changement climatique sur le rendement du riz dépendront des approches actuelles de changement dans les milieux d’exploitation rizicole. Par ailleurs, les impacts négatifs peuvent être évités par des mesures appropriées,notamment les changements des pratiques agronomiques, le développement des variétés de riz plus tolérantes à la température et une formation effective des fermiers

Does alternation increase water productivity when applying partial root-zone drying to tomato?

In developing countries, horticultural production relies on smallholder farmers who cannot access advanced irrigation technologies. In Ghana, tomato production does not match the increasing demand for this crop, especially during the dry season so there is a need to increase irrigated tomato production. Optimal application of low cost irrigation techniques can increase water productivity and therefore the irrigated acreage. Partial root-zone drying (PRD) is a water-saving irrigation technique that applies sub-optimal irrigation to half of the root-zone, while adequately irrigating the remainder. PRD increased water productivity compared to homogeneous drying in different crops including tomato. Although root-to-shoot signaling studies predict that the drying of the irrigated zones need to be alternated to maintain PRD effects, studies on the effects of alternation are scarce. To investigate the optimal PRD application technique in tomato we carried out a field trial in Kumasi (Ghana) on an improved bush-type cultivar (Petomech) where both alternated and fixed PRD alternation at 50% of ETc (crop evapotranspiration) were compared with full irrigation (100% ETc). Irrigation treatments did not affect fruit yield, increasing water productivity. Plant physiological responses to alternation were also assessed in a controlled environment experiment in Lancaster (UK) on a miniaturised, containerised PRD system (75% of ETc) using the dwarf cultivar Micro-Tom. PRD decreased fruit yield by ca 15% regardless of whether it was alternated or not. Whole-plant gas exchange and stem diameter variations did not differ between alternated or fixed PRD, even under high vapor pressure deficit, either during the drying cycles or upon re-watering. Stem growth was reduced early after applying PRD and was not affected by alternation. Contrary to previous reports, these results suggest that alternation has little impact on tomato yield, and so fixed PRD may be more readily assimilated by smallholder farmers

Growth, Development and Yield of Cassava Progeny as Affected by Nutrient Status of Mother Plant 1

Cassava is a very important staple crop in Ghana, contributing significantly to the country's Agricultural GDP. Majority of farmers in eight out of the ten regions in Ghana cultivate the crop due to its ability to grow on marginal lands. The crop has until recently seen little improvement in their husbandry practices. Cassava yields on farmers’ fields are low (8-10 t/ha) with potential yields of 30 to 40 t/ha. A major factor contributing to this low yield is the low soil fertility and the poor quality of the planting material. The study investigated the effect of fertilizer application of the mother plant on the growth, development and yield of progenies from these plants. Cassava genotype Dabo was sown in June 2013, at 1 m x I m at CSIR-Crops Research Institute, Kwadaso, Kumasi, Ghana. There were four fertilizer treatments: NPK 30:30:45, 60:30:45, 45:30:45, and Control. The experiment was arranged in a randomised Complete Block Design (RCBD) with three replicates. NPK was applied at one month after planting and Muriate of potash three months after planting. The mother plant was harvested in June, 2014. Cassava yields for all the fertilizer treated plots were significantly higher than the control plot (12.1 t/ha) with yield difference ranging between 68% (20.3 t/ha) and 278 % (33.7 t/ha) in the first year. Cuttings from the mother plants were planted with no fertilizer application in July, 2014. Progeny from the treatment that gave the highest yield in Year 1 (45-30-45, N:P:K) gave the greatest yield (24.0 t/ha) relative to the control (10.3 t/ha) in year two, (233%) higher. Commercial cassava planting material producers should boost the quality of the cassava planting material through fertilizing the mother plant. Farmers can also fertilize a small portion of their cassava farm and use cuttings from the fertilized plot as planting material. Key words: cassava, fertilizer, planting material, potential yields Croissance, développement et rendement de la descendance du manioc affectée par le statut nutritif de la plante-mère 1. Le manioc est une culture de base très importante au Ghana, contribuant pour environ 22% du PIB agricole du pays. Environ 90% des agriculteurs de huit des dix régions du Ghana cultivent la culture en raison de sa capacité à pousser sur des terres marginales. La culture a jusqu'à récemment vu peu d'amélioration dans leurs pratiques d'élevage. Les rendements de manioc dans les champs des agriculteurs sont faibles (8-10 t / ha) avec des rendements potentiels de 30 à 40 t / ha. Un facteur majeur contribuant à ce faible rendement est la faible fertilité du sol et la mauvaise qualité du matériel végétal. L'étude a étudié l'effet de l'application d'engrais de la plante mère sur la croissance, le développement et le rendement des descendances de ces plantes. Le génotype de manioc Dabo a été semé en juin 2013 à 1 mx 1 m au CSIR-Crops Research Institute, a Kwadaso, Kumasi, Ghana. Il y avait quatre traitements d'engrais: NPK 30:30:45, 60:30:45, 45:30:45 et Control. La conception expérimentale était un design de bloc complet randomisé (RCBD) avec trois répétitions. Le NPK a été appliqué un mois après le semis et le Muriate de potasse trois mois après la plantation. La plante mère a été récoltée en juin 2014. Les rendements de manioc pour toutes les parcelles traitées aux engrais étaient significativement plus élevés que la parcelle témoin (12,1 t / ha) avec une différence de rendement comprise entre 68% (20,3 t / ha) et 278% (33,7 t / ha) la première année. Les boutures des plantes mères ont été plantées sans application d'engrais en juillet 2014. La descendance du traitement qui a donné le rendement le plus élevé en année 1 (45-30-45, N: P: K) a donné le rendement le plus élevé (24,0 t / ha ) par rapport au témoin (10,3 t / ha), 233% plus élevé. Les producteurs commerciaux de matériel végétal de manioc devraient améliorer la qualité des plants de manioc en fertilisant la plante mère. Les agriculteurs peuvent également fertiliser une petite partie de leur exploitation de manioc et utiliser les boutures de la parcelle fertilisée comme matériel de plantation.Mots-clés: manioc, engrais, matériel végétal, rendements potentiel

Simulative Evaluation of the Response of Maize and some Dual-Purpose Legumes to Water and Nutrient Amendments

The study evaluated DSSAT's CERES-Maize and CROPGRO models for their effectiveness in simulating the growth of maize, groundnut, and cowpea under dynamic nutrient amendments and water management practices in field experiments. The experiments were laid-out in split-plot with water management (rainfed and irrigated) as main plots and fertilizer (organic and inorganic fertilizer) as sub-plots during the maize trial, while, water management treatment (irrigated and rainfed) was the main plot and variety as the subplot during the cowpea and groundnut trials arranged in three replications. The CERES-Maize model's RMSE-observations standard deviation ratio (RSR) for simulating maize grain yield under irrigated and rainfed were 0.1624 and 0.0317 respectively, while that for the maize biomass under irrigated and rainfed were 0.4027 and 2.1676 respectively. Also, the CROPGRO model's RSR for simulating groundnut grain yield under irrigated and rainfed were 0.1058 and 8.0592 respectively, while that for the groundnut biomass under irrigated and rainfed were 1.1154 and 0.0161 respectively. In addition, the CROPGRO model's RSR for simulating cowpea grain yield under irrigated and rainfed were 8.1625 and 0.1019 respectively, while that for the cowpea biomass under irrigated and rainfed were 0.2677 and 0.2630 respectively. From the results, it was concluded that the CERES-Maize model was more suited to effectively scope alternate management practices under maize production whereas more research is needed to be able to confirm the effectiveness of the model in our environment.Keywords: Crop production, CROPGRO, CERES-Maize, DSSA

Logistic analysis of factors and perception of smallholder rubber farmers to intercrop: a case study involving rubber and plantain intercropping system in Ghana

Even though rubber tree (Hevea brasiliensis) is a major tree crop and is lucrative for small holder' farmers in Ghana, the 6 years waiting period to maturity constraints its establishment. Intercropping of rubber with food crops has been found to be a solution to this production constraint in most rubber producing countries. The objective of this study was to empirically assess farmers' perception on rubber/plantain intercropping and factors that directly affect rubber farmers' decision to intercrop rubber plantations with plantain. A multistage sampling technique was used to select 200 rubber farmers from the Central and Western regions of Ghana. Both descriptive and logistic regression models were used to analyze the data. About 83% of the rubber farmers were males. Based on the logit model analysis, gender, level of education, household size, farm size, member of association and experience in rubber farming were found to have significant influence on the adoption of rubber/plantain intercrop. Respondents see the potential adoption of rubber/plantain intercropping system as a means to improve food security, farmers' income and livelihood. Non-governmental organizations, Ghana Rubber Estates Limited (GREL) and Government should focus on strengthening its extension arm to develop more interpersonal contacts with potential rubber farmers. Policy makers, researchers and extension providers should closely work together with rubber farmers in identifying suitable rubber/plantain spacing and varieties on a case by case basis to ensure effective adoption and scaling out.Keywords: Food security, Ghana, GREL, Livelihood, Rubber and plantain intercroppin