Keep your garden feeding you

 Here are some practical follow up crops to keep your garden feeding you: 

grow corn, spinach, lettuce after your cabbage.

 try to grow your roots after your peas and other leguminous to use up the quantity of nitrogen which these plants have stored in the soil. 

After you have harvested the onions, a crop of heading lettuce will grow well in the rich soil.

When you dig up your early potatoes use the grown for leeks to harvest in deep winter.

And if you do not want to sow late crops in the vacant ground in the garden, it is a good idea to sow cover crops such as clover or rye with the idea of turning under next spring. 

Doing this will add considerable fertility to the ground very little cost, and also such soils will hold moisture better next season.