Rainfall is light and, except on eroded soils, fertility appears to be fairly well maintained even under a grain-fallow system. Fibre can also be maintained by trash-cover farming which keeps as much straw and stubble as possible in the soil surface. Implements that will maintain a trash cover are essential for farming in this zone.
Regular rotations of grain and forage are rarely followed in Zone 1. With the low rainfall, soil fertility declines slowly and it is often difficult to establish forage stands. Forage crops do have a place in this area. They contribute to a more balanced type of farming, prevent soil erosion and improve soil structure. A portion of the cultivated land might well be sown to grass periodically and left down for about five years.
Crested wheat grass is widely used, particularly for re-grassing overgrazed ranges and for permanent seeding down of light soils that tend to drift readily. The grazing capacity of a good stand of Crested wheat grass is considerably greater than that of native range.
Sweet Clover is also useful in this zone, since it adds nitrogen to the soil. It should be seeded with the last grain crop before summer fallow.
Better moisture conditions in this zone mean more rapid soil depletion and a greater need for forage crops. Crested wheat grass and sweet clover will be the choice in the drier sections.
In districts of more plentiful moisture, alfalfa and brome grass may be grown to advantage. Throughout this zone, greater use should be made of sweet clover to improve soil fertility through its ability to take nitrogen from the air. Land should not be seeded to a cereal crop if more than eight to twelve years have elapsed since it was last down to a forage crop.
Forage crops should remain down from three to five years. If a satisfactory stand is established in the first year, three years of forage may be sufficient.
In the irrigated areas the more abundant water supply calls for increased use of forage crops. Not more than four or five grain crops should be grown in succession without a return to grasses or legumes. However, the readily available water offers a wider choice in selection of these crops. Alfalfa is the main hay crop since it fits well into most farm programmes on irrigated land.
Brome, creeping red fescue, timothy, Kentucky blue grass, orchard grass and the clovers, all thrive under irrigation. Forage should remain down from four to six years depending on the kind of mixture used and the density of the stand.
A good stand will benefit the soil more quickly than a poor one. Summer fallowing should not be necessary on irrigated land. A suitable crop rotation consisting of grain or specialty crops and forage crops should enable the production of a crop every year while at the same time weeds are controlled and the soil improved.
Land that is more than five to eight years away from forage should not be seeded to grain in this zone. Alfalfa and brome grass are the most useful forage crops, but all winter hardy grasses and legumes can be grown successfully. The most important of these are altaswede (red) clover, alsike clover, timothy, and creeping red fescue.
Creeping red fescue may be used to advantage since its extensive root system will add large amounts of fibre to the soil. Forage crops in Zone 3 should remain down from two to four years, depending on the kind of mixture used and the density of the stand. If a good stand is obtained in the year of seeding the desired soil improvement will take place quickly.
In this zone — the grey-wooded — land that is more than two to four years away from forage should not be seeded to grain. Legumes must be grown if the land is to yield profitable returns. Since, under natural conditions, the soil contains very little fibre, grasses are essential too. Alfalfa and the clovers, brome, timothy and creeping red fescue are all important forage crops in this area.
Forage should remain down from two to three years, depending on the kind of mixture used and the condition of the crop. A good stand will improve the soil more quickly than a poor one. In the improvement of grey-wooded soils, legumes and fertilizers should be used together.
Forage yields in this zone are commonly more than doubled by the application of fertilizer. Yields of grain following fertilized legumes also show remarkable increases. Sulphur, nitrogen and phosphate are the main elements usually lacking. Nitrogen can be supplied by growing legume crops but sulphur
and phosphate must be supplied in the form of commercial fertilizer.