Midterm effect of maize (Zea mays L.)-wheat (Triticum aestivum L.) rotations on grain yield and soil properties

In a five years experiment, the effect of crop rotation was examined on yield and soil physico-chemical properties in 200 hectares land of College of Agriculture- during 2010-2015 growing seasons Shiraz University, Shiraz, Iran,. Eight rotation systems consisted of 1: complete fallow (no planting), 2: continuous maize-wheat, 3: wheat rotation with alfalfa, 4: maize rotation with alfalfa, 5, 6, 7 and 8: fallow in one, two, three and four of ten growing seasons during five years using randomized complete block design with four replications. Shiraz wheat cultivar and SC704 maize hybrid were used. Results showed that the highest wheat grain yield (7706 kg.ha-1) and maize fresh forage (82100 kg.ha-1) obtained when sown in rotation with alfalfa. Fallow had positive effect on yield of both crops, up to four seasons for wheat and up to two seasons for maize. Continuous maize-wheat with higher soil salinity and lower amount of nitrogen (N), phosphorous (P), zinc (Zn), iron (Fe), copper (Cu) and manganese (Mn) led to significant reduction in yield compared to rotations with alfalfa or fallow for more than two seasons. Wheat and maize in rotations with alfalfa had higher soil nitrogen, phosphorous, iron and manganese which were associated with greater wheat grain yield and maize fresh forage. Micronutrients were greater in fallow systems and this might led to greater and stable wheat grain yield and maize fresh forage yield. It was concluded that rotation with alfalfa or 2-3 seasons fallow for maize and 4 seasons for wheat improved soil chemical conditions, and consequently had higher economical yield of wheat and maize.