Double cropping effects on forage yield and the field water balance

Double cropping is an option to increase feed production from a unit of land. However, summer crop yields may be depressed due to shortened length of growing season and elevated drought risk. We studied the effect of double cropping winter small grain silage crops (rye, Secale cereale L. and barley, Hordeum vulgare L.) on corn (Zea mays L.), soybean (Glycine max L.), and annual silage yields and soil water balance in no till and compared that with alfalfa (Medicago sativa L.). Precipitation, runoff, deep drainage, and soil water content were measured over a two-year period (variable precipitation), and crop evapotranspiration (ET_c) was estimated using the Penman-Monteith method. Small grains were planted in the fall after harvest of the main crops. Corn silage and soybean whole-plant yields were not significantly reduced by double cropping, so total annual silage yields increased with double cropping. Double cropping did not reduce runoff or deep drainage and did not affect soil water content compared with single cropping rotations, but alfalfa rotations occasionally generated less drainage and lower soil water contents. The estimated ET_c was higher in double than in single cropping systems during the fall and spring seasons due to transpiration by the winter small grain, but our measurements did not confirm these modeled double cropping effects. The water balance showed a likely over-estimation of drainage and possibly ET_c. Double cropping offers the potential to increase annual silage yields without affecting the water balance in Southeastern Pennsylvania.