Analysis of subsurface drainage for land use planning

The trend of increasing agricultural output in recent decades has been noted. To some extent this increase has been due to a myopic view on growth and development that involved an unabated exploitation of land and water resources with intensive use of complex technology. In this process, for the past few decades, man has influenced the natural state of the environment in order to create an ideal environmental condition for producing biomass and energy at a rate that surpassed all previous limits. Ibis remarkable achievement was, however, at the expense of a greater social cost. Today the harmful effect of these modifications can be seen in terms of a decline in natural habitats and an increase in various forms of pollution. Nevertheless, it would be a gross hypocrisy if one does not appreciate positive impacts of this increased agricultural productivity. Agriculture and its supporting industries are the backbone of our economies. Besides providing a continuous and cheap supply of food and raw material the agro-food industry has contributed significantly to the well being of our societies through an economic chain-effect.Despite all these negative and positive aspects, a surplus agricultural sector and an over-exploited environment are the realities of our time and have become a challenge to scientists. While the surplus agricultural sector has depressed commodity prices and as a result is threatening the survival of our farm communities, the over-burdened environment is becoming increasingly unsafe for various forms of life that depend on it.In order to avoid such problems we need to redefine various components of our planning procedures so that all possible cause-effect structures are incorporated in alternative plans. What we need are wen defined processes of decision making whereby resources are allocated over space and time according to the needs, aspirations, and desires of our societies within the framework of our technological inventiveness and giving due regards to the environment. It is to this end that the present investigation was embarked upon with the aim of examining one of the land use conflicts involving agricultural drainage and conservation of natural habitats. This detail examination comprised a review of the existing material delineating the conflict and a theoretical framework for evaluating trade-offs between the two land uses.The theoretical framework developed in this thesis is based on a systematic approach to economics of subsurface drainage (Figure 4.2 of this thesis). This systemic approach focuses on the biophysical cause-effect structure of drainage and its impacts from agricultural and enviromnental perspectives. The biophysical cause-effect structure of drainage involves a complex process that includes hydrological, biological, ecological, and finally economic linkages. These linkages have several components that are interrelated and their individual or collective impacts are observed when the hydrological linkage (i.e. lowering of the ground water) is set in motion. In order to examine the economic consequences of these linkages a system of performance indicators (SPI) was developed. The SPI system is rather a simplistic technique whereby all agricultural and enviromnental impacts of drainage are expressed in monetary equivalent. This system will allow a relatively less complicated comparison of all costs and benefits of drainage from agricultural and environmental perspectives. Hence, the framework presented in this thesis can be used as a decision- making tool to evaluate trade-offs between agricultural drainage and wetland conservation from farmer's (micro) and societal (macro) perspectives.Since the empirical testing of the entire framework was beyond the scope of this thesis, instead two sets of data (i.e. two case studies) were used to quantify the farmer's perspective on agricultural drainage. In order to test the approach under different conditions two separate sites and two entirely different crops were chosen.The first case study was based on some experimental data from IJsselmeerpolders, in the Netherlands. Although this set of data was obtained from an experimental field, some of its conditions, such as soil type (marine clay soil), represented a wide geographic area in the region and other parts (e.g., areas with river clay soils) of the country. Thus the investigation was not considered as an isolated experiment that could not be related to the actual farm situation. The study was designed to analyze the effect of drainage (subsurface) conditions and nitrogen fertilizer application on production of two apple cultivars, Cox's Orange Pippin and Golden Delicious. 'Me analysis was carried out in two parts: a statistical analysis to determine the effects of drainage conditions (i.e. different ground water regimes), yearly fluctuations, and nitrogen fertilizer application on apple production; and an economic analysis to determine economic viability of drainage investment for apple production. The general findings of these analyses were:1. There was a significant relationship between apple production and drainage classes (i.e. different ground water regimes) , annual climatic changes, and application of nitrogen fertilizer.2. Yield of Cox's apples responded more positively to drainageimprovements and a moderate application of nitrogen fertilizer.3. Drainage improvement resulted in 45 and 26 percent increase in theaverage yield of Cox's and Golden apples respectively.4. The highest yield levels for both cultivars were reached on the very well drained soils with a moderate application of nitrogen fertilizer. Excess nitrogen doses had a negative impact on the quality of apples.5. Drainage investment was highly profitable for apple production,provided moderate levels of nitrogen fertilizer were applied.The second case study was based on actual farm records (corn yields) representing eastern Ontario, Canada. This investigation was designed to determine the economic viability of subsurface drainage under different agroclimatic and soil conditions. The study was carried out in two parts. Ile first part was focussed on determining the change in physical yield resulting from subsurface drainage. The second component was an economic analysis examining the economic viability of subsurface drainage due to changes in physical yield and a shift in cropping pattern. Results of these analyses revealed that:1. As expected, the increase in physical yield due to subsurface drainagewas much higher on naturally poorly than on naturally imperfectly drained soils.2. The largest increase in physical yield due to subsurface drainage was found on light (mostly with impervious subsoils) as well as on heavy soils rather than on the medium textured soils.3. Despite relatively large increase in physical yields on heavier soils, the economic returns of drainage investment on these soils were actually low, mainly because of higher installation costs.4. It was also found that there was a substantial payoff in subsurface drainage investments if such investments are followed by a change in cropping pattern.The highlights of the study are elaborated in the summarizing chapter (i.e. chapter 10) of the thesis.