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109. Conditions of Successful Wheat Culture.—The yield and quality of wheat, and hence its successful growth, agriculturally considered, depend mainly upon these six conditions: (1) climate, (2) soil (including fertilizers), (3) variety, (4) methods of cultivation, (5) liability to disease, and (6) attack of insect enemies.
110. Effect of Climate Upon Geographical Distribution
According to the tenth census seventy per cent of the wheat of the United States was grown where the average January temperature was below freezing; eighty-five per cent was grown where the average July temperature was between seventy and eighty degrees, and sixty-five per cent where the mean annual temperature was between forty-five and fifty-five degrees. Too much weight must not be attached to this, as the soil, particularly in respect to its ease of cultivation, has greatly affected the distribution of wheat. Most of the wheat of the world, however, grows in regions of cold winters, although there are some noted exceptions, as California, Egypt and India. Taking the world at large, and including both spring and winter varieties, wheat has a very wide climatic range. Its range of successful culture, also, seems to be constantly extending northward, whether through climatic adaptation or from other causes seems less clear.
in. Effect of Climate Upon Quality.—Localities having widely different climate and soil have their peculiar varieties, which differ somewhat in composition but much more in physical characters, such as size, plumpness, hardness and color of grain, length and shape of spike and in length of straw. It seems to be quite conclusively demonstrated that these changes are more closely related to climate than to any other factor. (74) Some varieties of wheat, however, such as Fultz, have a very wide distribution.
Those localities which have extremes of temperature and rainfall, especially during the ripening period, generally have the hardest and reddest grains and the highest per cent of nitrogen, but are generally less plump and are smaller in size. Wheat of hot, sunny climates, with moderately dry weather during the latter part of growth, is brighter and makes better quality of flour the world over. The United States is particulary favored in this respect.
112. Effect of Climate Upon Growth.—Seelhorst found that a high moisture content in the soil during early growth caused a larger number of spikelets per head, and that a high water content at time of heading increased the number of developed blossoms per spikelet.1
A cool, prolonged, but not too wet spring, followed by moderately dry sunny weather during ripening, is most favorable to the largest yield of best quality. The influence of the length of the growing period on the accumulation of plant food and consequently upon yield may be illustrated by assuming that a maximum crop requires twenty-four pounds of nitrates besides those already f ormd in the soil, and by assuming that throughout the growing season four pounds of nitrates per month are produced by the nitrifying agents in the soil. Six months of growth would be necessary to produce a maximum crop. If climatic conditions should force the crop to maturity in five months, there would not be enough nitrates to produce a full crop, unless the same climatic conditions influenced the production of nitrates in the soil. The loss of nitrates during wet seasons has been
1 Jour. Landw. t!i (1900), No. 2, pp. 165-177, pis. 2. (E. S. R. XIII (1902), 125 ) found to be greater and the amount taken up by the wheat smaller.
113. Accumulation of Soil Constituents at Different Stages of Growth.—The wheat plant for its best development needs to have its early growth in the cool part of the year. A long period of growth consequent upon cool weather encourages tillering and gives better opportunity to get sufficient plant growth. Adorjan has shown that wheat takes up the greater portion of its food in the early stages of growth, stores it up, and draws upon it later for the development of the grain.1 (123)
At the Minnesota Station during two years the weight and composition of spring wheat was determined (1) at fifty days when it was eighteen inches high, (2) at sixty-five days when it was fully headed, (3) at eighty-one days when grain was in the milk, (4) at 105 days when wheat was ripe.
At the end of fifty days the plant had produced nearly onehalf its dry matter and nearly three-fourths its total mineral matter; when fully headed, sixty-five per cent of its dry matter and eighty-five per cent of its mineral matter. When the grain was in the milk the plant had produced ninety per cent of its dry matter and practically all its mineral matter. Nearly seventy-five per cent of the potash, eighty per cent of the phosphoric acid, and eighty-six per cent of the nitrogen was taken up in the first fifty days. The fiber was formed largely before the plant was fully headed; after the grain was in the milk a slight loss of fiber occurred in the plant. The starch stored up in the seeds was formed mainly during the last half of the period of growth.2
114. Winter Killing.—In a country of cold winters it is better to have the ground covered continually with snow. Alternate freezing and thawing with the plant exposed to the wind is very destructive to wheat. Winter wheat kills in two ways, by freez
Ijour. Landw. 50 (1902), No. 3, pp. 193-230. (E. S. R. XIV, 436.) 2 Minn. Bui. 29, pp. 152-160.
.ng to death and by being heaved out by alternate freezing and thawing. When the soil is bare, the soil temperature about the roots of the young plant will reach nearly that of the overlying air, while if covered with two inches of snow the soil may, if the low temperature is of short duration, be little if any below freezing
II. THE SOIL AND ITS AMENDMENTS.
115. The Choice of Soil.—The character of the soil affects the yield much more than the quality of the wheat. (74, 111) A. large proportion of the wheat is grown in this country upon glaciated drift soil, the controlling reason being the ease of cultivation and adaptation to the use of light machinery.
Throughout the winter wheat region between parallels 380 and 420 N. latitude, within which lies what is known as the "Corn-belt," two general types of drift soil are recognized: (1) clay soils, usually upland, light in color, tenacious in texture, requiring careful tillage, which is generally adapted to wheat and grass crops, and (2) loamy soils, usually lowlands or prairies, dark in color, full of organic matter and friable in texture, generally known as maize land, to which it is especially adapted. This latter is not so well adapted to wheat, because in unfavorable seasons the wheat is apt to winter kill. Where the first type of soil is predominant, wheat, meadows and pastures largely prevail, while where the second type is predominant, maize and oats are the prevailing crops. It is not so much that fair crops of wheat may not be obtained as it is that maize pays better that has brought about this result; although on this soil wheat, as just stated, is very liable to winter kill. On the other hand, on the clay soils maize not only does not do so well, but the grass crop reduces the labor of tillage and helps to maintain the fertility of the soil. There is still a third type of soil to be found in less quantity in river valleys, chocolate in color, less tenacious in texture than the upland clays, being composed of a larger proportion of silt than the clay and less organic matter than the black soils, but very fertile and equally adapted to either maize or wheat . It is on the first of these three types of soil that fertilizers have been found to be most advantageous. Generally speaking, the increase in yield of wheat on the second and third types of soil has not been sufficient to pay for the cost of the fertilizers.
116. Effect of Change of Soil on Yield.—The Indiana Station sent seed of Velvet Chaff grown seven consecutive years to four different counties in the State, and the seed received from the crop was sown the next year at the station alongside the seed retained at the station. There were only slight variations in the yield of wheat from the different localities.1 The Maryland Station found no material difference between Maryland and Kansas seed with six varieties.* Bolley concludes after testing wheat from different parts of North Dakota, representing all kinds of soil, that true varieties under like soil and climatic conditions will approximate a like product without reference to the parent soil.8 The Nebraska Station found that wheat of the same variety from different sections of the country showed considerable variation in the habit of growth, much to the disadvantage of seed grown east of the Missouri River.* At the North Dakota Station the average result of twenty-three tests with home grown seed and with wheat originally from this station but grown at the Minnesota Station from one to nine years, showed a gain of about 2.5 bushels in favor of the home grown seed. *
117. The Use of Fertilizers.—Nothing has been more clearly demonstrated than the fact that with an increased amount of fertilizers, the yield does not increase proportionately to the quan
1 Ind. Bui. 41.
s Md. Bui. 14.
8 E. S. R. VI (1896), 268.
* Neb. Bui . 72.
I N. Dak. Rpt . 1900, pp. 59-97.