SUGARCANE YIELDS IN THE IVORY COAST AS INFLUENCED BY SOIL WATER BALANCE OVER TWO CRITICAL GROWTH STAGES
By
CRÉPIN B. PÉNÉ and SYLVAIN G. KOULIBALY
SUCAF-CI Ferké Sugar mills, 33 rue des Brasseurs, 01 P.O. Box 1967 Abidjan, Ivory Coast
cbpene@yahoo.fr
KEYWORDS: Sugarcane Yield, Irrigation Management, Water Uptake, Limiting Factor, Ivory Coast.
Abstract
THE INFLUENCE of water deficit as a main cane yield limiting factor in the Ivory Coast
was investigated on two commercial sugarcane plantations, SUCAF Ferké 2 and Sucrivoire Zuénoula. A soil water balance model was used to assess water deficit over two critical growth stages, namely stem elongation and yield formation. Water deficit was correlated with cane yields. Under simulated rainfed conditions, average yields (from 1991 to 1997) at both sites were highly dependent (linearly) on the average crop water satisfaction ratio (ETa/ETm) over these critical growth stages. Under supplementary irrigated field conditions in Ferké 2 (irrigation water being considered in addition to rainfall), cane yields of early as well as late maturing sugarcane varieties were dependent on the average crop water satisfaction ratio over both growth stages. In Zuénoula, cane yield fluctuations were generally not predicted by the crop water satisfaction ratio, regardless of the cropping season considered. However, average cane yields obtained from year to year over the study period in both sugarcane schemes were highly dependent on the water satisfaction ratio. This shows the important contribution of water in predicting yearly variations of average cane yields produced on commercial Ivory Coast sugarcane plantations.
Introduction
Water deficit was shown to be the main factor limiting yield of sugarcane in the Ivory Coast, caused by unreliable rainfall, as well as the irrigation constraints of sugar mills, in terms of surface water, power availability or irrigation equipment (Péné, 1999; Péné and Tuo, 1996; Péné et al., 1997). However, cane yields obtained on commercial plantations are not always optimised by applying irrigation water, although the other key production factors are kept at their optimum levels. Moreover, yearly cane yield estimates are rather subjective and therefore unreliable.
The study aimed to understand the contribution of the soil water balance to yield, and particularly the influence of crop water deficit at two critical growth stages on cane yield variations over six consecutive cropping seasons (1991–92 to 1996–97).
Material and methods Site characteristics
The study was carried out on two commercial sugarcane plantations, SUCAF Ferké 2 and Sucrivoire Zuénoula, which are respectively located in the northern and central-western Ivory Coast. At Ferké 2, the climate is of the tropical dry type with a unimodal rainfall pattern averaging 1200 mm/year while, at Zuénoula, the climate is tropical wet with a bi-modal rainfall pattern averaging 1100 mm/year. Soils at both sites are basically ferrallitic or oxisols.
Water balance model
Crop water uptake was calculated by means of a water balance model based on the following equation (Belmans et al., 1983):
Type of crop Name Duration Early-season varieties Post-harvest at stem elongation March–July
Late-season varieties Post-harvest at stem elongation Pre-harvest at yield formation From one month of age to July From November to ripening in February or March
Fig. 1—Front line sprinkler irrigation system used in SUCAF/Ferké 2. Crop material
Commercial sugarcane varieties which were adapted locally for their tolerance to prevailing diseases as well as their performance in terms of sucrose yields were used (Table 2, Figure 2).
Table 2—Cane varieties used in SUCAF/Ferké 2, Sucrivoire/Zuénoula and in the
four Ivory Coast sugar mills (SUCAF Ferké 1 & 2, Sucrivoire Zuénoula & Borotou). Sugar mills
SUCAF/Ferké 2 Sucrivoire/Zuénoula All 4 Ivorian sugar mills NCo 376 M 3145 Co 740 Co 62175 B 37172 Ragnar Co 997 Co 740 Co 6415 Co 6304 B 46364 Co 449 R 570 Co 957
Fig. 2—An early season sugarcane crop (NCo 376) in SUCAF-CI/Ferké 1. Results
Rainfall pattern over the study period
At SUCAF Ferké 2 (Figure 3), the amount of rainfall averaged 1050 mm/year and 550 mm over the critical growth stage (from March to July). At Sucrivoire Zuénoula (Figure 4), total rainfall averaged 1200 mm/year and 670 mm over the critical growth stage.
Fig. 3—Average climatic data in SUCAF/Ferké 2 over the study period (1991–1997). 0 50 100 150 200 250 300
Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.
Months Wa te r de pths (m m) Rainfall ETo Pan Ev (A)
Fig. 4—Average climatic data in Sucrivoire/Zuénoula over the study period (1991–1997).
Soil water balance
Rainfed conditions
At Ferké 2, the correlation between cane yield and the crop water satisfaction index over the stem elongation stage was not significant.
This suggests a low contribution of rainfall to cane yield variations at this site. In contrast, the correlation was highly significant at Zuénoula, which therefore shows that cane yields were strongly dependent on rainfall pattern over the stem elongation stage.
Irrigated conditions
At Ferké 2, cane yields of early season varieties obtained on a yearly basis were predicted by the average crop water satisfaction ratio over the stem elongation stage (Figures 5 and 6).
At Zuénoula, cane yields were generally not well predicted by the crop water satisfaction ratio for either sugarcane variety.
However, over the study period, average cane yields obtained for all years on both sites were highly predicted by the average crop satisfaction ratio (Figure 7).
This shows in general how importantly water contributes to cane yield variations on a yearly basis in Ferké 2 as well as Zuénoula.
0 50 100
Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.
Months
Wat
e
Fig. 5—Simulated soil water balance under an early-season sugarcane crop in SUCAF/Ferké 2 during the 1991–92 cropping season with 62.6 tc/ha and 83.5%
ETa/ETm over the stem elongation stage.
Fig. 6—Relative cane yields in SUCAF/Ferké 2 as a function of water satisfaction ratio (ETa/ETm) over the critical growth stages (stem elongation and yield
formation), for five cropping seasons (1991–92 to 1995–96). -80 -60 -40 -20 0 20 40 60 80 100 120 140 March Ap ril May June July
10-days and months
Wat e r de pt hs (mm) or E Ta /ETm (%) Rainfall 0 Irrigation 30 Drainage 0 ETa/ETm 64 ETa -40 y = 1.21x - 5.57 R2 = 0,64 50 55 60 65 70 75 80 85 90 95 100 60 65 70 75 80 85 ETa/ETm (%) R el at ive can e y iel d ( % )
Fig. 7—Relative cane yields in Sucrivoire/Zuénoula as a function of water satisfaction ratio (ETa/ETm) over the critical growth stages (stem elongation and
yield formation), for three cropping seasons (1995–96 to 1997–98). Conclusion
Water deficit appears to be the factor most limiting to the production of sugarcane in the Ivory Coast. Thus use of a soil water balance model might significantly contribute to the prediction of cane yields.
As the average cane yields are highly dependent on rainfall, the Ivorian sugar industry should adjust its irrigation management strategy. Priority in the use of irrigation should be given to the March–July critical growth stage where climatic risk is high regardless of the type of cane variety (early or late-season crops), as well as at the yield formation stage of late-season varieties.
REFERENCES
Belmans, C., Wesseling, J. and Feddes, R.A. (1983). Simulation model of the water balance of a
cropped soil: SWATRE. J. Hydrol., 63: 271–286.
Eagleman, J.R. (1971). An experimentally derived model for actual evapotranspiration. Agric.
Meteor, 8: 385–394.
Péné, C.B. (1999). Le diagnostic hydrique en culture cannière et la gestion du risque climatique en
Côte d’Ivoire. Agric. Dév., 24: 74–80.
Péné, C.B. and Tuo, K. (1996). Utilisation du diagnostic pour le pilotage optimal de l’irrigation de
la canne à sucre en Côte d’Ivoire. Séch., 7(4): 299–306.
Péné, C.B., Chopart, J.L. and Assa, D.A. (1997). Gestion de l’irrigation à la parcelle en culture de
canne à sucre sous climat tropical humide, à travers le cas des régions nord et centre de Côte d’Ivoire. Séch., 2(8): 87–98. y = 1.91x - 80 R2 = 0.92 50 55 60 65 70 70 75 80 85 90 95 ETa/ETm (%) Rel a ti ve
INFLUENCE DU BILAN HYDRIQUE DURANT DEUX STAGES PHÉNOLOGIQUES CRITIQUES SUR LES RENDEMENTS
DE LA CANNE À SUCRE EN CÔTE D’IVOIRE
Par
CRÉPIN B. PÉNÉ et SYLVAIN G. KOULIBALY
SUCAF CI, 33 rue des Brasseurs, 01 P.O. Box 1967 Abidjan, Ivory Coast cbpene@yahoo.fr
MOTS-CLÉS: Canne à Sucre, Rendement, Gestion de l’Irrigation, Satisfaction Hydrique, Campagne de Récolte, Côte d’Ivoire.
Résumé
L’INFLUENCE du déficit hydrique comme principal facteur limitant des rendements de la canne à
sucre en Côte d’Ivoire a été étudiée, sur deux phases phénologiques critiques (grande croissace et prématuration), dans deux périmètres sucriers que sont SUCAF/Ferké 2 et Sucrivoire/Zuénoula. En simulant des conditions pluviales, les rendements moyens réels obtenus sur chacun des sites (de 1991 à 1997) sont étroitement liés à l’indice de satisfaction hydrique (ETR/ETM) des parcelles correspondant à ces phases critiques. Sous irrigation à Ferké 2, les rendements en canne des variétés de début de campagne ainsi que celles de fin sont fortement corrélés à l’indice moyen de satisfaction hydrique des parcelles durant ces deux phases phénologiques. À Zuénoula, par contre, les variations de rendements en canne ne s’expliquent généralement pas par celles de l’indice de satisfaction hydrique des parcelles, quelque soit la période de campagne considérée. Toutefois, les rendements moyens en canne obtenus, chaque année dans les deux périmètres sur la période d’étude, sont fortement corrélés à l’indice de satisfaction hydrique des parcelles. Cela montre l’importance du facteur hydrique dans la prévision des rendements moyens en canne dans les périmètres sucriers ivoiriens.
PRODUCCIONES DE CAÑA DE AZÚCAR EN LA COSTA DE MARFIL INFLUENCIADAS POR EL EQUILIBRIO DE AGUA DE LA TIERRA
DURANTE DOS ESTADOS DE CRECIMIENTO CRÍTICOS
Por
CRÉPIN B. PÉNÉ y SYLVAIN G. KOULIBALY
SUCAF-CI Ferké Sugar mills, 33 rue des Brasseurs, 01 P.O. Box 1967 Abidjan, Ivory Coast
cbpene@yahoo.fr
PALABRAS CLAVE: Producción de Caña de Azúcar, Gestión de Riego, Absorción de Agua, Factor Limitante, Costa de Marfil.
Resumen
SE REALIZÓ una investigación en dos plantaciones cañaverales comerciales; SUCAF Ferké 2 y
Sucrivoire Zuénoula, a propósito de la influencia del déficit de agua como factor limitante de producción en la Costa de Marfil. Se utilizó un modelo de equilibrio de agua terrenal para valorar el déficit acuático durante dos estados de crecimiento críticos, que son: el alargamiento del tallo y la formación del cultivo. El déficit de agua esta correlacionado con las producciones de caña de azúcar. Bajo condiciones de lluvia simulada, el promedio de producción (desde 1991 a 1997) en ambas plantaciones dependió en gran parte (linealmente) del promedio del ratio satisfactorio de agua de cultivo (ETa/ETm) durante los estados críticos de crecimiento. Bajo condiciones de cultivo de regadío suplementario (referido al regadío de agua adicional al agua de la lluvia), en Ferké 2 por ejemplo, la producción de caña tanto para las variedades de caña de azúcar tempranas como tardías, dependió en gran parte del ratio satisfactorio de agua de cultivo durante ambos estados de crecimiento. Por otro lado, en Zuénoula, la variaciones de producción cañaveral no se pudieron
