Does resource complementarity or prevention of lodging contribute to the increased productivity of rice varietal mixtures in Yunnan, China?

We conducted an experiment in Gejiu, Yunnan Province of China during the wet season of 2002 to examine the importance of resource complementarity and prevention of lodging in the fast-spreading practice of growing rice varietal mixtures in China to suppress rice blast disease and its associated damage. The hybrid rice variety Shanyou 63 and the glutinous or sticky rice variety Huangkenuo were used to study intra- and inter-varietal competition in the rice intercropping system. The experiment was laid out as a randomized complete block design in four replications with pure stands and mixtures of both varieties at different total planting densities and mixing ratios. In half of the pure stand treatments of glutinous rice a metal frame was installed to prevent lodging. The results showed that resource complementarity between the two rice varieties, resulting from niche differentiation, was marginal and did not greatly enhance the productivity of the rice varietal mixtures. In contrast, prevention of lodging of glutinous rice was identified as an important additional advantage of growing these rice varieties in mixture.