6 DEPAKTMENT OF AGRICULTUEE BULS. 176-200. 



Department Bulletin 190. — The Drainage of Irrigated Land — Contd. I'age. 



Protective devices for open canals 13 



Protective devices for covered drains 15 



Construction of drains 24 



Maintenance 28 



Subsequent treatment of land 29 



What drainage accomplishes 31 



Cost of draining 32 



Cooperative drainage 33 



Conclusion 34 



Department Bulletin 191. — Demurrage Information for Farmers: 



Introduction 1 



Definition and history of demurrage 1 



The farmer's interest in demiurage 2 



Regulation by the States 3 



Interstate regulation 4 



Provisions of the uniform demurrage code 5 



Exceptions to the uniform code 9 



A general sirrvey of State codes 10 



"Reciprocal demurrage " 12 



Other provisions of the State codes 14 



Special features of State codes 16 



Demurrage bureaus 18 



Conclusion 20 



Appendix. , 23 



Department Bulletin 192. — Insects Affecting Vegetable Crops in 

 Porto Rico: 



Introduction 1 



Thysanoptera and hemiptera. or sucking incects 2 



Orthoptera 4 



Coleoptera 5 



Lepidoptera 6 



Hymenoptera 9 



Dipfera - 10 



Summary 10 



Department Bulletin 193. — The Drainage of Jefferson County. Tex.: 



Introduction 1 



General description of Jefferson County 2 



The survey 7 



The drainage problem 8 



Run-off 10 



Proposed plan of drainage 13 



Estimate of cost 24 



Conclusion 32 



Appendix 33 



Department Bulletin 194. — The Flow of Water in Irrigation Chan- 

 nels: 



Introduction 1 



Nomenclature 2 



Historical 2 



Necessary field data for values of n 4 



Scope of experiments 7 



Equipment and methods employed for collecting field data 7 



Correction for velocity heads 15 



Elements of field tests to determine retardationvfactors in Kutter and Chezy 



formulas 16 



Description of channels 28 



The use of values of n 45 



Recommendations for values of n for different kinds of channels 47 



Estimation charts 52 



V^ariations of n in the same channel 58 



Conclusions 60 



Acknowledgments 61 



