EFFECT OF IRRIGATION REGIMES AT VARIOUS PHYSIOLOGICAL GROWTH STAGES On SUGARCANE QUANTITY AND QUALITY YIELDS

Abstract

The demand for food and energy is steadily increasing with increase of population growth rate. Irrigated agriculture assumed to make a major contribution to food security, all though it is the major consumer of water resources, unfortunately yields of irrigated crops is very low. At present, sugarcane is the most reliable food and feedstock and energy ( bioethanol) production since its farming technologies are already in place in Sudan, and currently, the country is in deficient production of sugar. The scope for further horizontal irrigation development to meet sugar requirements in the coming years, is however, severely constrained by decreasing water resources and growing competition for clean water. While on a global scale, serious water shortages are developing in the arid and semi-arid regions as existing water resources reach full exploitation. The situation is serious (exacerbated ) by the declining quality of water and soil resources. The dependency on water has become a critical constraint on further progress and threatens to slow down development, endangering food supplies and aggravating rural poverty. The great challenge for the coming decades will therefore be the task of increasing food production with less water, particularly in countries with limited water resources. For food Security and planning purposes , it is necessary to forecast crop yield before season end. With changing climate and environment worldwide water is becoming more scarce. In Arid and Semi-arid area the problem of water scarcity ( less supply ) , and increasing demand (domestic uses , Agriculture , industry and urban uses) necessitated better irrigation management and proper scheduling. To improve water efficiency it is essential to develop water management tactics to overcome problems of improper water scheduling (over–under supply ) for different crop growth stages. The aim of this study is to investigate the way sugarcane crop react to stress irrigation, leading to practical guidelines to assist extensionists, farmers and decision-makers in optimizing water use for optimal crop production. Accordingly, field trials were carried out for two seasons(2007/2008) in Gunied Sugar plantation experimental farm located in Gezira State, in order to study sugarcane growth and yield response to excess/ deficit irrigation imposed at each crop physiological growth stage. The experiment was a split-split plot design with factorial arrangement, completely randomized in 27 water treatments (adequate , excess and xvi deficit ) for each one of three growth stages( tillering , vegetative and maturity) in three replicates. Deficit irrigation scheduling is one way in which farmers practicing irrigation farming, can cope with the pressure to reduce water used for crop production in order to release more water for other sectors in need of it. In this study deficit irrigation is investigated as a valuable and sustainable production strategy in dry regions with limited water resources. By limiting water applications to certain growth stage, this practice aims to maximize water productivity and to stabilize – rather than maximize – yields. The soil in the study area is characterized with its poor internal drainage resulting in water logging when over irrigated. Excess irrigation trials were conducted to a certain impacts of timing of efficient management practices as a cheap solution of the frequent problem of over watering . Cultural practices followed are typical to those adopted by Gunied sugar plantation for variety Co6806 . Data collected includes: level soil moisture depletion using gravimetric method, inflow rate measured with vane flow meter, yield components (plant height, thickness, number of tillers), yield parameters (cane yield as weight, sugar content and juice quality), and water performance indicators(yield response factor and water use efficiency). Statistical analysis of the data and discussion of obtained results reveals that: Deficit irrigation at early stage of sugarcane growth produced higher cane yield and higher water use efficiency compared to other stages . In contrast, deficit irrigation at the late stage had a serious and drastic effect on final cane and sugar yields and hence, it may be regarded as the most sensitive stage. Although deficient irrigation imposed at vegetative stage produced lower cane yield compared to that of tillering stage , it resulted in the highest sugar content due to sugar recovery. Hence, deficit irrigation is recommended to be practiced at tillering stage, after well crop establishment, for optimum cane yield and high water use efficiency ,and late application of deficit watering had to be avoided completely. Excess watering applied at the early stage produced the lower yields of cane and sugars compared to other stages therefore should be avoided ,while excess watering imposed at the vegetative stage produced higher yields of cane and sugars compared to other stages . Therefore, acceptable level of over irrigation can be tolerated only at vegetative stage. This level need to be precisely determined by future studies. In addition more investigations need to be done on regular deficit irrigation at different soil moisture depletions at the early and vegetative stages of growth xvii for maximum economical yields of sugarcane crop and an improved water use efficiency. Yield response factor was estimated as 1.13for sugarcane crop, which match well with FAO value of 1.2 . Using the estimated crop response factor, crop–water production functions for sugarcane crop in Sudan can be developed to derive the productivity of the applied. It can be inferred from the irrigation scheduling protocol of excess/deficit irrigation of this study that the past policies of water resource management which adopt irrigation practices consistent with an abundant and inexpensive water supply to avoid moisture stress to strive for maximum yield need to be replaced by those practices that consider deficit irrigation as a key strategy for increasing on-farm water productivity in water-scarce dry areas and the risk associated with deficit irrigation can be minimized through proper irrigation scheduling (avoiding water stress at growth stages sensitive to water stress). Key Words: Deficit irrigation, yield formation