Irrigation scheduling of confectionery groundnut (Arachis hypogeaea L.) in Senegal using a simple water balance model
Introduction
The recent development of the Senegal river basin (Gay and Dancette, 1995) presents a new opportunity for groundnut production under irrigated conditions. The increase in irrigated areas should be accompanied by the search for export markets such confectionery groundnut production. However, the increase in the used amount of irrigation water could lead to a reduction in available water resources, which should be paid for and shared by more users. Agricultural research is therefore faced with the question of developing appropriate sustainable production techniques.
The effect of soil water availability on a number of plant development mechanisms has been considerably reported. For instance on groundnut or on pea, water stress reduces leaf area through leaf number and leaf size (Ong et al., 1985, Lecoeur and Guilioni, 1998, Lecoeur et al., 1995). In bean, sorghum and cotton, water deficit has also been manifested by an earlier leaf senescence (Karamanos, 1978, Rosenthal et al., 1987). Moreover, in a review on the effect of limiting available soil water to many cultivated species, Sadras and Milroy (1996) reported that leaf expansion showed higher sensitivity to soil water limitation compared to transpiration. Yet, when transpiration is affected by soil water status through the stomata closure (Jarvis and McNaughton, 1986, Comstock, 2002), the combination of the long-term effects on leaf area and of the short-term effects on stomatal conductance reduces the gaseous exchange and leads to a reduction of the canopy water consumption (Jones, 1992). Based on these results, groundnut yield may be regulated by the amount of water available to the plant during its development (Hammer et al., 1995). Concerning the quality management of the crop, Ramamoorthy and Basu (1996) reported that occurrence of water stress during flowering affects the number of mature pods per plant and the seed size. Nevertheless, reducing irrigation at the end of the peak-flowering stage generally results in yield (Nageswara Rao et al., 1985) and pod quality increases, in particular concerning their commercial grade (Nautiyal et al., 1991). These results show that the effect of water deficits depends on its intensity and time of occurrences. This points out the need to master irrigation scheduling.
Most available water balance models are based on the use of characteristics for each phase of plant cycle (Doorenbos and Pruit, 1977). In fact, water regime and farmer practices (plant density) have an important impact on vegetative plant development which renders ineffective the use of invariable crop coefficients for each developmental stage. Hammer et al. (1995) proposed an interesting simple model which included estimate of phenology, leaf expansion, biomass accumulation and soil water balance. However, most of the proposed parameters have been estimated for a temperate climate. Moreover, daily transpiration estimations are based on the calculation of the daily biomass increment involving the soil water module which could not be used independently.
The aim of this study is to develop and evaluate a model to simulate the fraction of transpirable soil water (FTSW) as proposed by Sinclair and Ludlow (1986) for two groundnut varieties cultivated in Senegal. The developed water balance model uses a set of simple equations which allows daily estimation of available soil water based on daily meteorological data, a succinct description of the soil characteristics as well as an estimation of leaf and root development. Based on the hypothesis that soil water status is the only factor that significantly influences the transpiration of the crops studied, this model provides a tool that could be used to schedule irrigation. From daily climatic data, hydrodynamic characteristics of the soil and LAI, the model permits to calculate the amount of water to be applied in order to reach a targeted FTSW. The results using the model to test targeted soil water status paths on confectionery groundnut production and water availability, under drip irrigation conditions are included in this paper.
Section snippets
Model development
The adopted original model is based on a pea model (Lecoeur and Sinclair, 1996), in which it is possible to simulate the fraction of transpirable soil water, which accounts for the amount of soil water available for the plant in the root zone area (George et al., 2000). The model considers the soil as a reservoir with two compartments, whose relative sizes vary in time with root growth (Fig. 1). The first compartment, explored by the roots, contains the soil water reserve. This compartment is
LAI growth and senescence curves assessment
Results obtained in 1994 and 1996 showed that, whatever the water treatment applied or the variety, observed phase 1 and phase 2 LAI data could satisfactorily be adjusted by a three parameters sigmoid curve and a straight line, respectively (treatment nos. 1–12 from Table 1). For Fleur 11 and GH 119-20 phase 1 (all treatments together), R2 values were 0.823 and 0.861, corresponding to RMSD of 0.81 and 0.60, respectively. For phase 2, R2 values were 0.712 and 0.631, with RMSD of 1.11 and 0.64
Conclusion
The developed model has an advantage in simulating soil and crop water balance based on data related to climate, soil, and onsite specific development status of the groundnut crop. This approach permitted to take into account all the environmental effects on the changes in plant leaf area. Consequently we limited as much as possible the model development to physic processes by integrating the plant architecture plasticity, one of the major adaptive responses of plants to their environment
Acknowledgements
The authors wish to thank the technicians at CERAAS for their assistance in collecting field data. They also wish to thank Dr. Harold Roy-Macauley and Dr. Serge Braconnier for suggestions to improve the paper and Yaye Couna Sylla for informatic assistance. They are also grateful to the “Comité National Interprofessionnel de l’Arachide” (CNIA) of Senegal and the European Union (EU) for their financial support.
References (34)
- et al.
Physiological responses of argentine peanut varieties to water stress. Water uptake and water use efficiency
Field Crops Res.
(2000) - et al.
Rooting depth and soil water extraction patterns of different crop in silty loam halustoll
Field Crops Res.
(1997) - et al.
Development and testing of an irrigation scheduling model
Agric. Water Manage.
(2000) - et al.
Stomatal control of transpiration: scaling up from leaf to region
Adv. Ecol. Res.
(1986) - et al.
Relationships between plant and soil water status in five field-grown cotton (Gossypium hirsutum L.) cultivars
Field Crops Res.
(1998) - et al.
Rate of leaf production in response to soil water deficits in field pea
Field Crops Res.
(1998) - et al.
Soil water thresholds for the response of leaf expansion and gas exchange: a review
Field Crops Res.
(1996) - Allen, G.R., Pereira, L.S., Raes, D., Smith, M., 1998. Crop Evapotranspiration. Guidelines for Computing Crop Water...
- et al.
Environmental and agronomic effects on growth of four peanut cultivars in a subtropical environment. I. Dry matter accumulation and radiation use efficiency
Exp. Agric.
(1993) - Chopart, J.L., 1980. Etude au champ des systèmes racinaires des principales cultures pluviales au Sénégal (arachide,...
Pilotage de l’irrigation avec IRRICANNE+
Agriculture et Développement
Hydraulic and chemical signaling in the control of stomatal conductance and transpiration
J. Exp. Bot.
Effect of temperature treatment on peanut vegetative and fruit growth
Peanut Sci.
Row spacing effects on light extinction coefficients of corn, sorghum, soybean and sunflower
Agron. J.
A peanut simulation model. I. Model development and testing
Agron. J.
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