Integrating rice and wheat productivity trends using the SAS mixed-procedure and meta-analysis

Long-term trends of crop yields have been used as a means to evaluate the sustainability of intensive agriculture. Previous studies have measured yield trends from long-term rice–rice and rice–wheat experiments in different sites from the slopes of individual site regressions of yield over time. The statistical significance of each site regression was determined but not that of the aggregate trend, which could give an indication of the magnitude...