Maintaining environmental and productivity sustainability of non-homogeneous furrow set in different agro-landscapes

The aim of this paper is to evaluate the impact of distribution uniformity on environment and productivity under furrow irrigation in different agrolandscapes in Europe and propose geographically oriented irrigation options. Various situations in free drained furrow plots in France and Bulgaria are analysed by field observations and modelling. Unlike studies based on a single furrow observation, these analyses take in to account global uniformity that is experienced by plant due to irrigation water distribution (downfield and transversal) when more then 30-40 simultaneously irrigated furrows are considered. FURMOD (Popova, 1990; Popova et al, 1996) and SOFIP (Maihol, 2001; Maihol et al., 2003) models are calibrated and validated with data from field observation. Then they are used to estimate deep percolation and runoff losses provoked by any specific irrigation practices. FURMOD is a model allowing the evaluation of water distribution, deep percolation and runoff losses depending on application time and depth, soil infiltration parameters, water deficit in the root zone when lateral nonuniformity of the advance process is taken into account. The estimated water application depths (WAD) are therefore inputs of a crop model for evaluating the impact of WAD heterogeneity on crop production and nitrogen leaching. SOFIP is a simulation model allowing analysing the impact of a furrow irrigation practice on the risks of deep percolation and crop productivity. Taking into account different sources of variability (discharge inlet, infiltration parameters) at the plot scale, the prediction capability of SOFIP aims at the improvement of the furrow irrigation systems management and design. These two different approaches are compared in terms of robustness and convenience of use. The role of irrigation practice in increasing the efficiency of the use of land and water resources in the different regions is defined. It is concluded that the maintenance of environmental and productivity stability requires better distribution uniformity and land preparation in case of high irrigation requirements. Strategies of furrow irrigation development may consist of different regional techniques for improving global distribution uniformity in the irrigation plot in order to produce maximum yield and reduce deep percolation and runoff. It is recommended to reduce furrows permeability by every furrow or every other furrow compaction before first flow, improve uniformity of stream advance by applying lower inflow rates and diminish runoff by closed-end furrows rather free draining furrows for in Tarascon, South France. Improved lateral uniformity of streams advance could both save irrigation water and mitigate environmental hazards in Sofia region, Bulgaria. It could be achieved by reducing variability of inflow at the furrows head, frequent application scheduling, surge irrigation respectively in advance and recession phase.