IRRIGATION AND ROTATION OF CROPS. 13 



ROTATION OF CROPS. 



By rotation is meant the special succession of crops grow- 

 ing upon the land for a series of years. This is very desirable 

 even on land in the highest state of cultivation, but it is very 

 difficult to lay down exact rules to be followed. 



Reasons for Rotating Crops. — We rotate crops for at least 

 six reasons. (1) To avoid insect enemies, as in the case of 

 onions and turnips, which are often liable to serious insect in- 

 juries when grown more than one year on the same land. Tur- 

 nips are especially liable to injury from insects when grown 

 in the same place successively. (2) To avoid injuries from 

 fungous diseases, i. e., in case of potato and beet scab, onion and 

 melon rust, corn smut, etc. (3) To increase the amount of 

 humus in the soil, and for this purpose we may seed down the 

 land to grass or clover. (4) To deepen the soil and add nitro- 

 gen to it as well as humus, as when clover is grown on the land. 

 (5) To get rid of weed seeds in the soil. (6) To use the plant 

 food in the land to best advantage, since crops vary very much 

 in the amount of the different elements which enter into their 

 composition. Leguminous crops, like clover, peas, beans, etc., 

 improve the land on which they grow, while most other crops 

 exhaust the soil. Some plants excel others in their power to 

 search for plant food, or to take plant food from the soil. Some 

 plants feed near the surface largely, while others take their 

 food mostly from a lower level. Root crops should not follow 

 root crops, nor should vines follow vines for many years in suc- 

 cession on the same land. 



QUESTIONS— CHAPTER 1. 

 On Vegetable Gardening Adapted to Students and Others. 



1. What location and soil is best for early crops? 



2. What location and soil is best for late crops? 



3. Under what conditions will it pav to irrigate? 



4. When should the land be mulched? 



5. What is meant by cultivation? 



6. What is humus and how does it affect the soiP 



contain? ^^^^ ^^^'^ ^^^^ water and how many barrels does it 



8. When will it pay to pump water for irrigation? 



9. Flow may a good, small, cheap reservoir be made? 



10. What kind of land is best adapted to irrigation? 



11. Give six rules for applying water to land 



12. hat is meant by sub-irrigation? 



13. What is meant by rotation of crops? 



14. Give six reasons for rotating crops 



15. What crops improve the land on which they grow and why? 



