Irrigation in the South

IR R IG A T IO NINT H ESO U T H Arthur]. Hawley and David W. Bunn* This article p resents the results o f a p relim inary inv estig ation into the p ractice o f irrig atio n in the So uth. (1) A ltho ug h irrigatio n is an ag ricultural techniq ue w id ely used thro ugho ut the w o rld , its use in m any hum id areas o f the w estern w o rld is a relativ ely recent inno vation. (2) G eo g rap hic study o f this ag ricultural techniq u e m ainly has been lim ited either to m ore arid clim ates o r irrigatio n has been co nsid ered as o nly o ne segm ent o f the land use system . T h e autho rs kno w o f no o ther stud ies w hich have exam ined irrigatio n thro ugho ut the so utheastern U nited States. IRRIGATION DEFINED. Fo r purposes o f this stud y irrigatio n is d efined as the intentio nal ap p licatio n o f w ater to a p lanted area to p ro vid e all o r a p art o f the p lants’ w ater requirem ents. This m ay b e acco m p lished in a w ide v ariety o f w ays. Recent experim ents have show n so m e success w ith sub­ surface irrig atio n. (3) In this m etho d p lastic pipes are buried in the soil b eneath the cro p row s. Reg ularly sp aced o rifices release a m etered am ount o f w ater w hich, id eally , w ets the ro o t zo ne w itho ut reaching the surface o f the so il. Fu rro w irrig atio n is w id ely used fo r row cro ps in the w estern United States. In this m etho d w ater is allo w ed to run d ow n furrow s betw een the p lanted row s until the so il is saturated to a certain d ep th. A variatio n o f this m etho d , flood irrigatio n, is used in the rice-g ro w ing areas o f the So uth. Sp rinkler irrigatio n p ro bably is the m o st co m m o n ty p e used in the so uth­ eastern states. In this m etho d w ater und er pressure is sp rayed o ut abo v e the p lanted area and allo w ed to fall like rain. Th e equ ip m ent used to ap p ly the w ater in sp rinkler irrigatio n varies w id ely. It bro ad ly m ay b e classed into m o ving and statio nary system s. M o v­ ing system s either rev o lve in a circle aro und a central pivo t po int o r move in a straig ht line dow n the field . H o w ev er, they are unusual in the So uth and w ill no t b e co nsid ered further in this d iscussio n. Statio nary system s are either p erm anently installed o r m ov able. Pip e in m o v able system s is univ er­ sally alum inum and m ad e up o f a series o f interlo cking lengths. Variations o ccu r in the pipe d iam eters, no zzle sp acing and heig ht, and sprinkler o rifice d esign. T h e o nly essential d ifference betw een m o v able system s and p erm anent statio nary system s is the rep lacem ent o f labo r by cap ital inv est­ m ent in the p erm anent system . A RECENT PRACTICE? Thro ug ho u t most o f the So uth irrigatio n has been * D r . H...