1、 - 1- TR-42 Agriculture and Drainage “Inseparable Science” Research Summary 2002 105 Decker Court, Suite 825, Irving, TX 75062 P: 469-499-1044 F: 469-499-1063 www.plasticpipe.org - 2- Foreword This report was developed and published with the technical help and financial support of the members of the
2、 PPI (Plastics Pipe Institute). The members have shown their interest in quality products by assisting independent standards-making and user organizations in the development of standards, and also by developing reports on an industry-wide basis to help engineers, code officials, specifying groups, a
3、nd users. The purpose of this technical report is to provide important information available to PPI on the importance of drainage for the agriculture industry. This report has been prepared by PPI as a service of the industry. The information in this report is offered in good faith and believed to b
4、e accurate at the time of its preparation, but is offered without any warranty, expressed or implied, including WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Any reference to or testing of a particular proprietary product should not be construed as an endorsement by PPI, which
5、does not endorse the proprietary products or processes of any manufacturer. The information in this report is offered for consideration by industry members in fulfilling their own compliance responsibilities. PPI assumes no responsibility for compliance with applicable laws and regulations. PPI inte
6、nds to revise this report from time to time, in response to comments and suggestions from users of the report. Please send suggestions of improvements to the address below. Information on other publications can be obtained by contacting PPI directly or visiting the web site. The Plastics Pipe Instit
7、ute (469) 499-1044 http:/www.plasticpipe.org Originally published July 2002 Reviewed and Reaffirmed March 2008 - 3- Agriculture and Drainage Inseparable Science Introduction US agriculture is an important contributor to the worlds food supply and a major component of the US economy. Nearly one-fifth
8、 of the worlds agricultural exports are shipped from the US. We have a heritage of productive agricultural lands and favorable climate that provides us with a comparative advantage. (Bucks, 1992) All agricultural soils require drainage. Natural drainage processes are not sufficient for agricultural
9、production on about 25% of the cropland in the USA and Canada. Artificial or improved drainage is necessary to produce crops on these lands. Improved drainage is needed on over 50 % of the cropland in some states and provinces. (Skaggs and Breve, 1991) Current agricultural production would be very d
10、ifficult to sustain if not for the drainage technology that has been developed over the past decades. Agricultural drainage continues to play a vital role in the sustainability of the worlds food and fiber production. Drainage technology development and research has been a cooperative effort between
11、 universities and public and private sponsoring organizations. The purpose of this white paper is to summarize many of the issues relating to agriculture, drainage and water quality and much of the research that has been performed. This information will be used to formulate a platform to support the
12、 on-going drainage activities and direct future developments and research. - 4- History of Drainage It has been said that those who ignore lessons from history are doomed to repeat them. This section is a brief compilation of historical documentation that drainage has not always been for agricultura
13、l production alone. In many instances, drainage served the purpose of making lands productive and even habitable. Historically, water management for agricultural purposes can be traced to Mesopotamia some 9,000 years ago. A major reason for the decline and disappearance of some ancient civilizations
14、 based on irrigation was their failure to heed the need for drainage. Drainage, the practice of removing excess water from agricultural land, has its origin at least 2,500 years ago when Herodotus wrote about drainage works near the city of Memphis in Egypt. Marcus Porcius Cato, 234 to 149 BC, appar
15、ently wrote the first specific directions for draining land. Land drainage is also apparent in the records of the Greek, Egyptian, and Roman civilizations. Land drainage to re-claim areas adjoining the North Sea in England began in the tenth century. The Dutch began converting land by draining and d
16、iking around 1550. Russia inaugurated drainage works in 1710 to make St. Petersburg habitable. (Economic Research Service, 1987), (Donnan) Much of the United States was not habitable or capable of agricultural production in its pre-development condition. Much of East central Illinois, for example, w
17、as“swampy land considered worthless for farming. Problems of human health were frequently reported such as epidemics of malaria, cholera, milk sickness, ague, and fever. Plagues of mosquitoes and flies were also reported. It is easy to understand the account of the young man who refused to trade his
18、 horse and saddle for a full section (640 acres) of swampy land in that period.“ (Economic Research Service, 1987) A 640-acre tract would sell for more than three million dollars at the highest agricultural land prices in that same area within the last several years. Pickels (1925) noted that Govern
19、ment Land Office records show that one-fourth of Illinois and still larger portions of other states were swampland. Twenty-one counties in northwestern Ohio and northeastern Indiana included much low land originally too wet to cultivate. Much of the land in north central Iowa, at the time of settlem
20、ent, was in shallow sloughs too wet for normal cultivation. Large areas in western Minnesota, northeastern Arkansas, the gulf plains of Texas, and the delta areas of Mississippi and Louisiana were originally swamp and overflow areas. Drainage permitted cultivation of these areas. (Economic Research
21、Service, 1987) The report on Longs expedition to the source of the St. Peters River in 1823 stated, “Near to this house we passed the state line which divides Ohio from IndianaThe distance from this to Fort Wayne is 24 miles, without a settlement; the country is so wet that we scarcely saw an acre o
22、f land upon which a - 5- settlement could be made. We traveled for a couple of miles with our horses wading through water, sometimes to the girth. Having found a small patch of esculent-grass (which from its color is know here by the name of bluegrass), we attempted to stop and pasture our horses, b
23、ut this we found impossible on account of the immense swarms of mosquitoes and horse flies. From Chicago to the place where we forded the Des Plaines, the country presents a low, flat and swampy prairie, very thickly covered with high grass, aquatic plants, and among others, the wild rice.” (Economi
24、c Research Service, 1987) The first known colony-wide drainage law was enacted in New Jersey in 1772. A City of New Orleans drainage outlet was constructed around 1794. Patterns for molding the first subsurface drains in the United States were recorded as imported from Scotland in 1835. (Economic Re
25、search Service, 1987) Early interest in the United States was not confined to development and enhanced agricultural production, but also stressed human health aspects, as illustrated by the draining of Central Park in New York City in 1858. In recent years, these health benefits were taken for grant
26、ed, or overlooked. Most of the great swamps and extensive breeding grounds for mosquitoes have been eliminated, although just in the last few years mosquito-born diseases, such as the Nile virus, have become a concern in many parts of the United States. Drainage in the United States occurred in two
27、primary developmental periods, during 1870-1920 and during 1945-1960. The first period was initiated around 1830 when increased public pressure was brought to Congress to release federal swamp and wetlands for private development. By 1920, more than 53 million acres out of a total of 956 million acr
28、es of US farmland had received some form of drainage. The United States Department of Agriculture (USDA), 1982 Natural Resources Inventory (NRI) inventory identified about 107 million acres of wet soils as being prime or adequately drained, of which 72 percent was then cropland. (Economic Research S
29、ervice, 1987) The NRI of 1982 indicated that nearly 28 million acres of existing non-irrigated crops and pastures had drainage problems, of which 15-20 percent were also considered wetlands. More recently, an added 12 million acres of rural land have been found to have at least a medium potential fo
30、r drainage and conversion to crop production. (Brown and Zucker, 1998) An estimated 110 million acres of agricultural land in the United States benefited from artificial drainage as of 1985. At least 70 percent of this drained land is in crops, 12 percent in pasture, 16 percent in woodland, and 2 pe
31、rcent in miscellaneous uses. (Economic Research Service, 1987) In eastern Canada over 6.2 million acres of farmland had been tile drained, as of 1992. (Madramootoo, et. al, 1992) It is estimated that the accumulated total investment in drainage since 1855 is $56 billion (1985 dollars). The average U
32、S real cost of providing subsurface - 6- drainage has fallen to $415 / acre from 1965 to 1985 which reflect the impact of drainage technology: trenching machines, corrugated plastic tubing installed with laser controlled high-speed trenchers or plows, and computerized design methods and models. (Eco
33、nomic Research Service, 1987) On state and regional basis, approximately 40 percent of the crops in North Carolina are grown on poorly drained soils. The drainage of cropland has been one of the most important components of land management in eastern North Carolina with drainage projects initiated a
34、s early as the late 1600s. (Evans and Skaggs, 1987. Real estate values for 256 predominately agricultural counties throughout the Eastern States with a high incidence of drainage averaged 27 percent more than values in 1,422 other agricultural counties, according to an analysis of 1982 Census of Agr
35、iculture data. (Economic Research Service, 1987) In Minnesota, although the percentage of cropland drained is lower than other Midwestern states, the 1985 NRI estimates for total cropland acres drained (6.37 million) are significant. (Brown and Zucker, 1998) Drainage, while currently viewed as an ag
36、ricultural production practice, has accomplished many purposes in water management, conservation and improvement of human health conditions throughout human development history. - 7- Effects of Drainage Drainage practices are broadly viewed as having both strengths and challenges. The following disc
37、ussion is to point out the diversity and interaction of drainage effects. This section must be read in context with the following one on water table management and sub-irrigation to gain an overall feel for the existing research and its variability in results. The effects of drainage can be categori
38、zed broadly into ten groups. These ten groups will be discussed: soil aeration, soil moisture and trafficability, nutrient / pesticide effectiveness and transport, soil temperature, toxic substances and disease, soil erosion and flooding, plant health and crop yield, water supply, and salinity contr
39、ol. All of the impacts are positive from an agricultural perspective and illustrate the value of drainage technology to agricultural production. The sum total of the effects indicate that agriculture, as we know it, would be un-sustainable in many regions of the world despite the challenges in water
40、 quality. Soil Aeration: The first purpose of a system designed to drain land for agricultural production in humid areas is to improve soil aeration. Water logged soils decrease the air exchange between soil and the atmosphere resulting in a decrease in O2 aroundthe plant roots and an increase in CO
41、2. It has been found that at low O2concentrations there is a decrease in mineral content in plants. Low O2concentrations in the soil also exert an influence on the growth rate. Aeration conditions in soils have a large influence on the availability of nitrogen. (Van Schilfgaarde, 1974) The better so
42、il aeration resulting from good drainage permits deeper and more extensive root development and a more favorable environment for beneficial soil microorganisms. (Palmer, 1977) Soil Moisture and Trafficability: Several factors make drainage a necessity for agricultural production on some land. These
43、factors include slow soil permeability, flat or depressional topography, restrictive geologic layers underlying the soil profile, and periods of excess precipitation. (Brown and Zucker, 1998) Performing farming operations when the soil is too wet results in soil compaction, soil structure degradatio
44、n and equipment becoming stuck during field operations. (Van Schilfgaarde, 1974) Compaction on agricultural land from the use of production equipment on wet soils also creates a layer that restricts the downward movement of water. Compaction research conducted by the USDA and the University of Minne
45、sota provided new insight into how soil water content affects the potential for soil compaction. This research points to the benefits of subsurface drainage to - 8- reduce compaction, and furthermore the need to maintain existing drainage systems. (Brown and Zucker, 1998) Reduction in labor has forc
46、ed farms to larger and larger sizes and more mechanized equipment, reinforcing the need to pay attention to trafficability. (Irwin, 1981) Trafficability is a term that has been used to describe the capability of a soil to permit the movement of a vehicle over the land surface. Trafficability in agri
47、culture means being able to perform the required farm operation in such a way as to create a desired soil condition or to get an operation done expediently. Drainage plays an important role in all aspects of trafficability for farm operations. The effect of lack of timeliness in performing farming o
48、perations may range from complete crop failure, if planting is delayed too long, to reduced yields if tillage, weed control, harvesting, or other operations are not performed on time. (Van Schilfgaarde, 1974) Research in Indiana showed that most of the measurable improvements in soil tilth and organ
49、ic matter in the cover crop and rotation treatments were greater in the presence of subsurface drainage than in its absence, and no-till treatments performed better with subsurface drainage. Perhaps the most significant benefit of subsurface drainage is in areas of a field where surface drainage is poor in some years the swales without subsurface drainage had enough ponded water to destroy the crop in that area, whereas drained plots were able to more quickly remove the ponded water. (Brown and Zucker, 1998) Drainage removes soil water and at the same time makes more s
