Variations in yields of spring wheat, barley and oats as a consequence of sowing time during the period 1970-1979 on three soil types

The effect of sowing time on the yields of spring wheat, barley and oats was studied in a ten-year trial at Tikkurila, southern Finland. Six different sowing times -at roughly four-day intervals were studied. The first seed was sown immediately after the soil had dried sufficiently for cultivation.
The second or the third sowing time appeared to be the most suitable in general, but there were great variations between the years depending on the weather conditions and soil type. Very early sowing did not yield the best results, but in a dry year, very late sowing could be even more detrimental.
With respect to giving good yields, silty clay soil was more sensitive to dry periods than sandy clay or clay loam soil. The reduction in yields could be very sharp, especially in dry years, and yields decreased with advanced sowing time. It was possible to obtain good yields from sandy clay soil even in dry years and despite late sowing.
The growing time was unaffected by the sowing time. There were great differences between different years: in dry years, the growing time was shorter than in wetter years. In dry years, the growing time was short but the yield was often low, too. In years, with enough rain, the growing time was longer and the yields could be better, too. Rain in June, in particular, appeared to increase crop yields.