Dryland farming and dry farming encompass specific agricultural techniques for the non-irrigated cultivation of crops. Dryland farming is associated with drylands, areas characterized by a cool wet season (which charges the soil with virtually all the moisture that the crops will receive prior to harvest) followed by a warm dry season. They are also associated with arid conditions, areas prone to drought and those having scarce water resources.
Dryland farming has evolved as a set of techniques and management practices used by farmers to continually adapt to the presence or lack of moisture in a given crop cycle. Groundwater supply is often the result of melted snow and ice in climates that experience high precipitation in the winter and dry heat in the summer. Water from nearby watershed sources can also be used in dry farming, and some believe that the use of dry farms could solve not only food shortage challenges in small communities but also climate change concerns.
In marginal regions, a farmer should be financially able to survive occasional crop failures, perhaps for several years in succession. Survival as a dryland farmer requires careful husbandry of the moisture available for the crop and aggressive management of expenses to minimize losses in poor years. Dryland farming involves the constant assessing of the amount of moisture present or lacking for any given crop cycle and planning accordingly. Dryland farmers know that to be financially successful they have to be aggressive during the good years in order to offset the dry years.
Dryland farming is dependent on natural rainfall, which can leave the ground vulnerable to dust storms, particularly if poor farming techniques are used or if the storms strike at a particularly vulnerable time. The fact that a fallow period must be included in the crop rotation means that fields cannot always be protected by a cover crop, which might otherwise offer protection against erosion.
Some of the theories of dryland farming developed in the late 19th and early 20th centuries claimed to be scientific but were in reality pseudoscientific and did not stand up to empirical testing. For example, it was alleged that tillage would seal in moisture, but such "dust mulching" ideas are based on what people imagine should happen, or have been told, rather than what testing actually confirms. In actuality, it has been shown that tillage increases water losses to evaporation.[1] The book explores the effects that this had on people who were encouraged to homestead in an area with little rainfall; most smallholdings failed after working miserably to cling on.
Dry farming depends on making the best use of the "bank" of soil moisture that was created by winter rainfall. Some dry farming practices include:
thumb|left|Wheat Dryland Farming in Behbahan, Iran
Dry farming may be practiced in areas that have significant annual rainfall during a wet season, often in the winter. Crops are cultivated during the subsequent dry season, using practices that make use of the stored moisture in the soil. California, Colorado, Kansas, South Dakota, North Dakota, Montana, Nebraska, Oklahoma, Oregon, Washington, and Wyoming, in the United States, are a few states where dry farming is practiced for a variety of crops.
Dryland farming is used in the Great Plains, the Palouse plateau of Eastern Washington, and other arid regions of North America such as in the Southwestern United States and Mexico (see Agriculture in the Southwestern United States and Agriculture in the prehistoric Southwest), the Middle East and in other grain growing regions such as the steppes of Eurasia and Argentina. Dryland farming was introduced to southern Russia and Ukraine by Ukrainian Mennonites under the influence of Johann Cornies, making the region the breadbasket of Europe. In Australia, it is widely practiced in all states but the Northern Territory.
thumb|Fields in the Palouse, Washington State
The choice of crop is influenced by the timing of the predominant rainfall in relation to the seasons. For example, winter wheat is more suited to regions with higher winter rainfall while areas with summer wet seasons may be more suited to summer growing crops such as sorghum, sunflowers or cotton. Dry farmed crops may include grapes, tomatoes, pumpkins, beans, and other summer crops.
Dryland grain crops include wheat, corn, millet, rye, and other grasses that produce grains. These crops grow using the winter water stored in the soil, rather than depending on rainfall during the growing season.
Successful dryland farming is possible with as little as 9inches of precipitation a year; higher rainfall increases the variety of crops.
See main article: Desert farming. thumb|An example of a dryland farming paddock
As an area of research and development, arid-zone agriculture, or desert agriculture, includes studies of how to increase the agricultural productivity of lands dominated by lack of freshwater, an abundance of heat and sunlight, and usually one or more of: Extreme winter cold, short rainy season, saline soil or water, strong dry winds, poor soil structure, over-grazing, limited technological development, poverty, or political instability.
The two basic approaches are: