Effect of different harvesting periods on grain yield and stalk silage quality of maize

The influence of the harvesting date of maize (CK: mid dough stage, harvesting on traditional date; S1: Late dough stage, harvesting delayed one week; S2: Early full ripening stage, harvesting delayed two weeks; S3: Mid full ripening stage, harvesting delayed three weeks; and S4: Late full ripening stage, harvesting delayed four weeks) on grain yield, and the nutritional value of straw and silage was investigated to determine the optimum harvesting date with a “Maize-Soybean” relay intercropping system in southwestern China. The results showed that the grain yield first increased together with increasing harvesting date until it reached a plateau. Grain yield was the highest at S2 being 9.47% higher than that of CK. The dry matter content (DM), acid detergent fiber (ADF), and neutral detergent fiber (NDF) of straw gradually increased together with the harvesting date. The ADF and NDF of CK, S1, and S2 were not statistically different; however, they were significantly lower than those of S3 and S4. The soluble carbohydrate content significantly decreased with the increasing harvesting date, but it was greater than 8% of that of DM. The pH values of silage significantly increased with the increasing harvesting date but were lower than 4.2, whereas the lactic acid content decreased (P<0.05). Propionic acid and butyric acid were not detected in all treatments. Ammonia nitrogen/total nitrogen in each treatment increased but was less than 5% of that of DM as harvesting date increased. In conclusion, the optimum harvesting date of corn was at the late dough stage to early full ripening stage in the southwest region, which guaranteed the highest grain yield and nutritional value.