Red clover cover crop studies 1987-1990
In 1987-90 seven trials were conducted in Middlesex and Huron Counties in southwestern Ontario to study the effect of time and method of control of a red clover cover crop on the growth and yield of corn. Drought conditions during late spring and summer in 1988-89 affected the performance of the cover crop and main(corn) crop.Excessively moist conditions in the spring of 1990 affected plant emergence and final plant stand especially on the spring tillage treatment. Results from three years of study indicate that in general those treatments which included the use of a mechanical method for controlling red clover resulted in grain corn yields approximately 11% higher than those achieved with the average no-till treatments, although the effect was not always statistically significant. However, this may he related to the previous crop stubble. Those sites which had red clover underseeded to winter wheat reported the greatest reduction in grain corn yield under no-till conditions compared to sites which had oats or oats and barley as the stubble crop. Under mechanical methods of red clover control the amount of soil surface residue cover left after planting was unacceptable from an erosion control standpoint.The chemical kill treatments provided somewhat lower corn grain yield with excellent residue cover remaining after planting.The mechanical kill treatment using the chisel plough produced yields which were similar to the October chemical kill treatments and may be used as an alternative to using the moldboard plough. The amount of dry matter collected from each of the treatment plots was related to the date and method of control of the red clover. The chemical treatment applied in May recorded the greatest amount of dry matter after planting followed by the April timing whereas the least amount (if any) was collected on the moldboard plough treatments. Results of the rainfall simulation indicated that the mechanical kill treatments (moldboard and chisel plough) recorded significantly higher runoff volumes, soil losses as well as total phosphorus losses compared to either ofthe chemical kill treatments (October and April). The difference in the results obtained for the chemical kill treatments for the above parameters were not significant indicating that the time of the red clover kill did not affect the erosion control of these treatments. In addition, no significant differences between the chisel and moldboard plough treatments were reported for these parameters.