Leguminous plants fix atmospheric nitrogen and make it available to the soil. In the given data, it is evident that average yield of corn is more when legumes like Monantha vetch, hairy vetch and Austrian peas are grown before the corn.
The average yield of corn grown on barren land is better than the one on which grass like rye was grown. But, comparing the barren land yield with those on which legumes were grown, the average yield of corn is the maximum on which legumes were grown.