Salt/Salinity Tolerance of Common Horticulture Crops in South Dakota. Relative Crop Yield (%) 20 SENSITIVE (S)

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1 Grdens igrow.org SEPTEMBER 206 SDSU DEPARTMENT OF AGRONOMY, HORTICULTURE & PLANT SCIENCE Slt/Slinity Tolernce of Common Horticulture Crops in South Dkot Review nd Revision: Lnce Stott SDSU Lecturer Originl Publiction: John Bischoff Assistnt Professor, Wter Resources Reserch Institute Hl Werner Professor, Extension irrigtion specilist, SDSU Agriculturl Engineering Deprtment Slt Tolernce Plnts vry tremendously in their bility to tolerte slt in wter. Their growth cn be restricted by the stress of pulling wter wy from the slt. Soil slt level slinity is one of severl stresses tht limit plnt growth. The slinity stress referred to in this fct sheet is the osmotic stress tht limits the vilbility of wter stored in the soil. This publiction does not consider the permebility problem cused by sodium tht reduces the mount of wter put into storge. The publiction Slinity & Sodicity Mngement from Montn Stte University vilble t lndresources.montn.edu/swm/documents/sw%20 2%20updted.pdf gives more informtion bout slinity nd sodicity problems. Seprting slinity stress from other plnt stresses is difficult becuse incresed slts lter the ionic chemicl blnce in plnts nd ffect wter vilbility to plnts. Therefore, slinity problems my contribute to other clsses of plnt stress. A reltionship of reltive crop yield compred to the slinity of the soil solution (electricl conductivity of soil solution extrct) is shown in Figure. The clsses re sensitive (S), modertely sensitive (MS), modertely tolernt (MT), tolernt (T), nd unsuitble for crops. Reltive Crop Yield (%) SENSITIVE (S) MODERATELY SENSITIVE (MS) MODERATELY TOLERANT (MT) TOLERANT (T) UNSUITABLE FOR CROPS Electricl Conductivity of Soil Sturtion Extrct (EC e ) (ds/m) Figure. Reltive crop yield compred to the slinity of the soil solution. If your line does not intersect n upper right line for the slt tolernce clss, there would be no yield reduction from slinity. An exmple of modertely sensitive crop nd soil slinity vlue of 0.0 ds/m is shown s line in Figure. Follow up from 0.0 (on the horizontl xis) to the MS line, then drw line to the left to get bout 45% reltive crop yield. This yield would be the highest you could expect for modertely sensitive crop t this level of soil slinity. Fctors Influencing Slt Tolernce Growth stge of the plnt is very importnt when considering slt tolernces. Mny plnts re extremely sensitive to soil slt during germintion or in the erly seedling stge. Most experiments hve evluted slt tolernce only on more mture plnts. To use Figure, red the vlue of the soil slinity on the horizontl xis nd follow it upwrd until it intersects the upper right hnd line of the SALT TOLERANCE CLASS for the crop tht interests you. Then drw line horizontlly left to intersect the verticl reltive yield xis nd red the number. This would be the percent yield obtinble with these slt conditions. Vrieties nd rootstocks of specific crops cn be quite vried in their sensitivity to slt. Some vrieties re known to be much more tolernt thn others within the sme species. Be sure to red the footnotes in the tbles regrding slt tolernces nd vriety differences. The nutrition level of the plnt (i.e. soil fertility) when under stress my ffect the plnt s bility to tolerte Pge

2 slt. Fertiliztion usully improves plnt s bility to tolerte slt. Fertiliztion beyond the plnt s needs, however, does very little to improve slt tolernce. Excessive fertilizer, which cn be slt-bsed, my even contribute to soil slinity. Climtic environment hs much to do with plnt s bility to tolerte slt. High temperture, low humidity, nd high winds increse evportion nd mke the plnt more susceptible to slinity; this cn cuse symptoms similr to wter stress. High ir humidity benefits slt-sensitive crops more thn slt-tolernt plnts. High tempertures decrese ny plnt s bility to tolerte slt. Chemicl ion toxicity ffects plnts tht my be sensitive to specific individul ions. It my ffect the plnt either by climtic ir or wter crriers or through the soil. Boron is n ion tht some plnts re very sensitive to in low concentrtions. In South Dkot, quifers with high concentrtions of sodium lso my hve high concentrtions of boron. Nutritionl imblnce s result of too much slt my occur if some slts re in certin proportion. For exmple, high concentrtions of clcium sulfte (CSO 4 ) my tie up some phosphtes into complexes tht re too insoluble for plnts to use. Soil nd Wter Anlyses Slinity (soil slt levels) cn be determined by testing. Smple soil depths by lyers to help determine if nd where slts occur in the gretest concentrtions. Shllow soil depths cn be smpled with spde during moist conditions. Deeper root zones cn be smpled esier with hnd soil probe or truckmounted soil smpler. Collect composite smples throughout the field to get representtive verge of the field. If there re trouble spots tht you suspect re cused by slt conditions, smple them seprtely from the rest of the field. South Dkot Stte University no longer nlyzes soil smples commercilly. For list of lbs tht cn nlyze your soil smple visit: To determine how much slt is in the wter you re using to irrigte, collect representtive pint of wter nd hve it nlyzed for types nd levels of slts. The testing fcility will lso usully interpret the comptibility of the wter with generl soils. South Dkot Stte University no longer nlyzes these types of wter smples. For list of fcilities tht cn nlyze your irrigtion wter visit: wter-smple-nlysis-nd-interprettion. Tolernt Horticulturl Crops The slinity level of the soil t which reductions in yield could be expected for individul South Dkot horticulturl crops, ssuming ll other stresses re not limiting, is shown in Tbles nd 2. This is the threshold slinity level or the 0% yield reduction column. The columns indicte the expected yield reduction if the slinity is t given level over the growing seson. The MAXIMUM column signifies the soil slinity level of the root zone rooting depth ssocited with vrious crops t which little to no yield cn be expected. The root zone for lflf my be up to 0-2 feet deep, wheres for strwberries it my be only 0-8 inches deep nd for blckberry only 2-3 feet deep. Implement reclmtion procedures before this level of slinity is pproched, or grow more slt tolernt crops. Grden nd Vegetble Crops Asprgus, beets, nd sqush re the most slttolernt, common vegetble crops grown in South Dkot. Onions, pes, crrots, okr, nd strwberries re mong the most slt-sensitive grden crops in this stte (see Tble ). Consider strwberries s n exmple. If the verge soil slinity of the root zone for the entire growing seson for strwberries ws round 2.7 ds/m, potentil yield would probbly be reduced bout 50% (50% yield reduction column for strwberries is 2.5). If your production gol for strwberries ws 0 qurts per unit, slt levels of 2.7 ds/m would reduce the mximum yield to only 5 qurts per unit (00% - 50%) x 0 = 5. The root zone for strwberries my be only to.5 feet deep. Woody Fruits Most woody fruits re very sensitive to slts in soils. These include pples, pricots, blckberries, Pge 2

3 Tble. Slt tolernce for grden crops. Slinity level (ds/m) for different yield loss columns of vrious crops. CROP ROOTING RATING b Yield decrese to be expected for certin crops due to soil slinity 0% EC E 0% EC E 25% EC E 50% EC E MAXIMUM EC E Asprgus D T Ben M S Beet, red M MT Broccoli S MS Brussel sprouts S MS* Cbbge S MS Crrot S S Culiflower S MS* Celery S MS Corn, sweet D MS Cucumber S-M MS Eggplnt M MS* Lettuce D MS Muskmelon S-M MS* Onion S S Prsnip D S* Pe M S* Pepper M MS Potto S-M MS Pumpkin D MS* Rdish S MS Spinch S-M MS Sqush, scllop D MT Sqush, zucchini M MT Strwberry S S Sweet potto D MS Tomto D MS Turnip M MS Wtermelon D MS* These dt re pplicble when rootstocks re used tht do not ccumulte N+ or Cl- rpidly or when these ions do not predominte in the soil. b Rtings re S=sensitive; MS=modertely sensitive; MT=modertely tolernt; T=tolernt to slts. *Rtings with n * re estimtes. EC E = Electricl conductivity of the sturtion extrct of the verge root zone (ds/m). boysenberries, cherries, currnts, gooseberries, ornges, peches, pers, plums, nd rspberries (see Tble 2). Consider grpes s n exmple. If the verge soil slinity of the root zone for the entire growing seson for grpes ws round 4.2 ds/m, you could nticipte pproximtely 25% reduction in potentil yield (25% yield reduction column for grpes is 4.2). If your yield gol for blckberries ws 500 lbs per unit, slt levels of 4.2 would reduce the mximum yield to only 375 lbs per unit (00% - 25%) x 500 lbs = 375. For grpes, the root zone my be bout 2 to 3 feet deep. Slt Mngement Dringe Slt problems often occur in soils of poor internl dringe. Low permebility soil lyers my restrict Pge 3

4 Tble 2. Slt tolernce for woody fruit crops in South Dkot. Slinity level (ds/m) for different yield loss columns of vrious crops. CROP RATING b Yield decrese to be expected for certin crops due to soil slinity 0% EC E 0% EC E 25% EC E 50% EC E MAXIMUM EC E Apple S ApricotC S Blckberry S Boysenberry S Cherry, sweet S* Cherry, snd S* Currnt S* Gooseberry S* GrpeC MS Pech S Per S* Plum; PruneC S Rspberry S These dt re pplicble when rootstocks re used tht do not ccumulte N+ or Cl- rpidly or when these ions do not predominte in the soil. b Rtings re S=sensitive; MS=modertely sensitive; MT=modertely tolernt; T=tolernt to slts. c Tolernce is bsed on growth rther thn yield. *Rtings with n * re estimtes. EC E = Electricl conductivity of the sturtion extrct of the verge root zone (ds/m). the flow of wter out the bottom cusing deep percoltion to be then continue with much slower thn evpotrnspirtion (ET) removes wter out the top. In such situtions, choose crops tht cn tolerte the slt without much yield reduction, nd/or, instll rtificil drins to llow the removl of leching wter nd slts from soils. If rtificil drin lines re instlled, do it ccording to county, district, or stte dringe lws to prevent pssing slt/wter problem from one lndowner to nother. Fruit Crops Becuse fruit crops in South Dkot usully represent smll res nd usully re not grown commercilly, the vilble mngement per unit re rtio is high. Therefore, mulching, rtificil drining, hrvesting rinwter to supplement existing wter supplies, etc. my be economiclly fesible compred to growing fruit crops commercilly on lrge res. Irrigtion Irrigtion mngement cn be used to decrese the level of slts in the root zone of the crop. As the slinity of irrigtion wters increses nd sesonl rinflls decrese, the window of mngement for slt becomes smller nd smller. Permebility of the subsurfce soils is importnt for slt mngement. There is bttle between moving sufficient slts downwrd beyond the root zone nd evpotrnspirtion bringing wter nd slts bck towrd the surfce. The blnce of slts cn be better monitored if the soil moisture content nd dynmics re known, since the slts move with the wter during the irrigtion seson. Tensiometers or moisture blocks cn be used to monitor the soil wter t different depths. Refer to Extension publictions FS 876, Irrigtion Mngement: Mesuring Soil Moisture, nd FS 899, Irrigtion Mngement: Using Electricl Resistnce Blocks to Mesure Soil Moisture, for more informtion on monitoring soil wter. These publictions re still ccessible nd contin relevnt informtion. However, newer soil moisture mesurement technologies re lso now vilble. For more informtion, refer to the Soil Wter Sensors section of Irrigting Corn in South Dkot vilble here: resources/ pdf When you mnge irrigtion wter to reduce slts, remember tht other mobile chemicls cn move with Pge 4

5 the wter s well. The publiction Reducing Nitrte Losses from Drined Lnds vilble t org/up/resources/ pdf gives more informtion on the movement on nitrte nd the potentil effects on ground nd surfce wter. Slts in the root zone re dynmic nd tend to chnge with climtic chnges. For well-drined soils, wetter periods tend to push slts further down in the root zone, wheres drier periods bring slts nerer to the surfce. In poorly drined soils, wetter periods tend to bring the wter tble closer to the surfce. In wetter conditions, the slt moves with the wter (upwrd) s the wter tble rises. Poorly drined soils usully hve higher slinity in wetter periods thn during drought. If these fcts re known, selection of crops for plnting ccording to their slt tolernce cn be used ccording to climte cycles nd soil dringe clssifiction. Obviously, plnning for nnul crops is esier thn for perennils. Averge Root Zone Slinity (ds/m) Irrigtion Wter/Rinfll Rtio (IW/RF) Figure 2. Reltionships of verge root zone slinity, leching, irrigtion, nd rin depths. When irrigtion wter is used to replenish soil profiles during the growing seson, slt is ssocited with both surfce nd ground wter. Even wter considered good for irrigtion in South Dkot of 0.8 ds/m electricl conductivity (600 milligrms per liter) would hve 0.82 tons of slt for every cre-foot of wter. The publiction Irrigtion Wter Qulity Stndrds nd Slinity Mngement Strtegies from Texs A&M provides more informtion on irrigtion wter qulity nd its potentil effects on soil slt levels. tmu.edu/publictions/b-667.pdf Irrigtion dds slt to the soil with the wter. The more soluble slts such s sodium sulfte (NSO 4 ), sodium bicrbonte (NHCO 3 ), sodium chloride (NCl), nd mgnesium chloride (MgCl 2 ) cuse more plnt stress thn less soluble slts such s clcium sulfte (CSO 4 ), mgnesium sulfte (MgSO 4 ), nd clcium crbonte (CCO 3 ). Therefore, some of these slts my need to be mnged more crefully to prevent buildup in the root zone. If nturl leching does not occur, leching with irrigtion wter on better drined soils cn help move slts downwrd where they do less hrm to growing crops. The leching frction is defined s the mount of wter pushed pst the bottom of the root zone DIVIDED by the totl mount of wter received into the soil. Unfortuntely, the leching frction is very much controlled by the existing subsurfce soils nd geology, nd finer-textured soils re more difficult to mnge for slts becuse the response time to leching my spn yers compred to only weeks for outwsh (corse subsoils). Figure 2 shows the reltionship between verge root zone slinity, irrigtion wter nd rinfll depths, nd leching frctions for given irrigtion wter slinity of 2.0 ds/m (high slinity). The verge root zone slinity is bsed on weighted crop wter use of 40% from the top qurter of the root Zone, 30% from the second qurter, 20% from the third qurter, nd 0% from the bottom qurter of the root zone (Figure 3). As the mount of irrigtion wter pplied increses nd rinfll decreses, the irrigtion wter/rinfll rtio (IW/RF) increses, the verge root zone slinity increses, nd higher leching frction is needed to keep slt levels below certin point. Figure 2 is bsed on receiving inches of frost-free rinfll during the growing seson. This is good verge number to use for centrl South Dkot (see Figure 4). There is considerble slt removl over the winter months s vpor moves up through the soil profile during freezing conditions leving the slts behind. The quntittive extent of the distilling depends upon the wter tble position, the soil moisture content, depth of snow cover, nd soil texture. Not much is known bout the slt exclusion phenomenon in res Pge 5

6 where soils become frozen, but something hppens tht keeps slts below the root zone in mny cses of long-time irrigted fields in South Dkot. Rrely do soils rech the higher levels of slts s shown in Figure 2 when irrigted with high-slinity wters. Slt precipittion nd freezing conditions pper to ccount for much of the reduction in slinity levels in soil root zones in South Dkot. Evpotrnspirtion Runoff Chnges in soil wter storge Deep Percoltion Rinfll Irrigtion Upwrd Flow Rooting Zone Depth - D Bottom of root zone of mture plnt 40% 30% 20% 0% Figure 4. Averge norml growing seson precipittion in South Dkot (April - October 3) for verge root zone slinity over the rnges of IW/RF, wheres, wter of EC of 3.0 ds/m vries by more thn three times (from 3.0 to bout 0.0) over the IW/ RF rnge. 9 Figure 3. Soil wter blnce (fter Cssel, 984) nd the percent wter extrction from bsic crop root zone (fter Pir, 975). Frost-free rinfll vries considerbly over the stte from high of 20 inches in the southest to 0-4 inches in the northwest. Therefore, the IW/RF rtio for the southest for corn my be round 0.6, wheres, it my be closer to 2.0 in the northwest. Two resons ccount for tremendous difference in potentil soil slinity: More wter pplied contributes to more slt. There is less dilution of soil wter from slt-free rinwter. Averge leching frctions under non-irrigted conditions will vry from lmost zero in northwest South Dkot with tight subsoils, to s much s 0.4 in estern South Dkot under high spring rins over shllow soils with corse subsoils nd deep wter tbles. Figure 5 shows the reltionships of verge root zone slinity nd irrigtion wter slinity for vrious slt levels in irrigtion wter for constnt leching frction of 0.0. Figure 5 is bsed on inches of frost-free rinfll. The rinfll mount is constnt in the IW/RF rtio. This grph shows how low slt wters re much esier to mnge thn higher slt wters. For exmple, n irrigtion wter of 0.25 ds/m chnges very little in Use Figures 2 nd 5 to consider exmple for grden or fruit crop in centrl South Dkot. Assume tht the crop needs 30 inches of wter to obtin expected yields. If inches of IW with wter qulity of 2.0 ds/m is pplied nd inches of frostfree rinfll is received, the IW/RF rtio is.0. If leching frction of 0.0 is ssumed (for every 0 inches of wter pplied t the surfce, inch is lost below the root zone), then n verge soil slinity of pproximtely 5.4 ds/m is pproched for stedy stte conditions. This ssumes no precipittion of slts, no uptke by plnts, no horizontl flow, or no distilling of the wter by freezing conditions during winter months. Averge EC of Root Zone (ds/m) Irrigtion Wter/Rinwfll Rtio (IW/RF) Figure 5. Reltionships of verge root zone nd irrigtion wter slinity nd irrigtion nd rinfll depths Pge 6

7 As cn be seen from Figure 2, for high slinity wters (2.0 ds/m, or 2.0 tons of slt per cre-foot of wter), the verge soil slinity cn go up rpidly even when 0% of the wter is lost out the bottom of the root zone. Generlly, the verge soil slinity vlues in Figure 2 cn be considered s mximum for South Dkot. Mny of the slts in the stte re gypsum (CSO 4 ) tht precipitte out t lower concentrtions, nd upwrd movement of wter s the soil freezes in the winter distills some of the soil wter. Reducing Slt Stress in the Grden Here re some wys to reduce slt stress for crops grown in the grden: Test soil nd wter slinity to determine the extent of the problem. Mulch round the bse of grden crops. Liberlly pply ny mulch to minimize evportive wter loss. Mny times grden crop root zones re shllow nd lose wter more quickly thn deep rooted crops. Develop lower-slt wter source, if vilble. If more thn one wter source is nerby, determine the slt lod in ech, nd determine which will lest ffect the plnts you re growing in your grden. If you hve limited supplies of ech source, you my wnt to use the better qulity wter on sensitive crops (i.e. strwberries) nd poorer qulity wter on tolernt crops (i.e. sprgus). Instll subsurfce rtificil dringe. This llows for removl of excess slts nd wter in the soil. This would help in recliming severe slinity problem, nd, lso, would be helpful in mintining slinity problems below certin level. A plce to grvity drin the wter nd slts is essentil when this mesure is used, nd should be plnned in dvnce of the instlltion of the drins. Wter frequently but thoroughly. If soils re kept moist, slinity stress will be reduced, becuse slts concentrte s the wter is used by evpotrnspirtion nd the slts re left behind. Wtering too often in shllow mounts will contribute to growth of diseses nd fungus on plnts, nd concentrte root growth ner the surfce. Wter the grden erly in the dy to reduce slinity stress during the het of the dy, nd to reduce the likelihood of disese development during the night. If reclmtion of soil slinity cnnot be ccomplished by the bove procedures, consider moving the grden re to new loction tht hs much less slt in the soil. If the surfce nd internl soil dringe is good (medium to corse textured soils), try overwtering to lech slts below the root zone. This is best done in the utumn of the yer fter most plnts hve been hrvested. Cre must be tken to reduce erosion on sloped grdens. Hrvest rinwter from nerby buildings. Rinwter hrvested from 25 x 40 building will provide bout one dditionl inch of slt-free wter to the grden for 0 by 20 re. (Assuming 75% collection efficiency, nd 0.25 rinfll). You cn either use storge tnk to collect the wter nd pump the wter to the grden, or, if the slope permits, route wter from the down spouts to grvity irrigte your grden. If the ltter method is used, good residue nd/or mulch used on the grden surfce will help reduce erosion. Informtion published by: SDSU Extension is n equl opportunity provider nd employer in ccordnce with the nondiscrimintion policies of South Dkot Stte University, the South Dkot Bord of Regents nd the United Sttes Deprtment of Agriculture. Lern more t igrow.org Publiction: Pge 7