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Early seeding of annual grain crops in temperate climates is desirable as yields are usually higher when these crops start growth early. In recent years, seeding on frozen uncultivated soil has been tried in an attempt to achieve early growth. How ever, most of the annual grain crops are still seeded in previously cultivated soil. Hence, it is important to know the probability of conditions suitable for early cultivation and for seeding in temperate regions. In humid regions the soil is usually saturated first thing in spring and considerable drying has to occur for the soil to reach a condition suitable for cultivation. The soil moisture content of the cultivated layer may be used to determine if the soil is in a suitable condition. Previous workers (1, 8, 11) reported that a soil is tractable when the moisture content is near field capacity. This was checked for the procedures derived in this paper by measuring the moisture content of the surface layers of a loam-textured soil prior to the first cultivation in spring. Estimation of soil moisture from re corded precipitation and computed values of daily evapotranspiration is a common practice (2, 6, 18). The same techniques can be used for a well-drained soil with no crop cover in spring provided that the dates are known when snow has completely melted and soil thawed. These have been estimated by previous workers (12. 15) from readily available temperature and snowfall data.
estimation of spring workdays from climatological records
Selirio, I.S. and D.M. Brown 1972. ESTIMATION OF SPRING WORKDAYS FROM CLIMATOLOGICAL RECORDS. Canadian Agricultural Engineering 14(2):79-81.
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