F ertilizer Rate ofnutrient Application, Ibs/ A

Transcription

1 Ptassium Fertilizatin and Hw t Effects Yield and Quality f Alfalfa by Rland D. Meyer, Extensin Sil Specialist, LAWR Dept., Davis, and Marsha Campbell Mat thews, Fann Advisr, Stanislaus Cunty, Mdest High prducing alfalfa uses large amunts f sil r fertilizer ptassium, abut 4 5 punds (K) per tn (485 bs K2/tn). n a number ffields, ptassium fertilizatin may be necessary t maintain frage prductin at its maximum. Fertilizatin with ptassium is knwn t have a number f effects n the yield and quality f alfalfa. t is the intent f this presentatin t give a brief review f past research as well as give preliminary infrmatin frm a field experiment initiated earlier this year. The functins f ptassium in plant grwth are numerus as ptassium influences phtsynthesis, respiratin, translcatin and many enzyme systems. Fertilizatin with ptassium when sils are unable t supply sufficient amunts results in large yield respnses. Reduced availability f ptassium can lead t a reductin in plant grwth and ccasinally in crp quality.respnse frm ptassium additins is first bserved when the rate f regrwth is mre rapid fllwing a harvest. The rapid rate f regrwth allws the alfalfa t cmpete mre aggressively against weeds and insects which results in lnger stand life. ncreased disease resistance may be anther factr that can be attributed t ptassium fertilizatin. Ptassium is knwn t imprve the level f carbhydrates stred in alfalfa rts. Greater stand persistence is the result f a cmbinatin f these factrs. Ptassium fertilizatin increases the ptassium cntent f alfalfa and affects the cncentratin f ther elements. t has been bserved in numerus cases that whenever a nutrient additin results in large alfalfa yield increases, many, if nt all ther element cncentratins will be reduced. Research indicates that ptassium additins tend t increase prtein in nly a few cases and a mre general result is that prtein cntent is decreased. Ptassium additins generally reduce calcium, magnesium, sdium and ccasinally sme f the micrnutrients. Experiments including higher rates f applied ptassium shw that ptassium cncentratin cntinues t increase lng after any yield increase is bserved, clearly indicating "luxury cnsumptin". Maximum yields are usually assciated with plant ptassium cncentratins in midstem samples f % and in the tp 6 inches f the plant f2.2.5%. Extremely high cncentratins, in excess f3. %, may be undesirable in alfalfa because the reduced calcium and ther element cncentratins effect the animal utilizatin f the alfalfa frage. Lwer rates f applied ptassium t maintain alfalfa ptassium cncentratins in the % range in midstem tissue samples r 2.2.5% range fr tp 6 inch samples wuld reduce fertilizer csts and yet insure adequate ptassium is available t prduce high yields. Reductins in the cncentratin f sdium in alfalfa by ptassium may be f sme benefit in Califrnia and ther Western States because f the high sdium levels in the sils and in the alfalfa plant. Ptassium fertilizatin reduces the magnesium cncentratin in the plant but with generally high magnesium levels in the sils and alfalfa f Califrnia, this is f minr 127

2 cncern. There are hwever sandy sils where magnesium as well as ptassium levels may be lw fr the prductin fhigh yielding alfalfa. Ptassium surces such as ptassium chlride (6) increase the cncentratin f chlride. This may be f sme benefit in suppressing the effect f certain diseases. High rates f ptassium chlride in a single applicatin ften create a chlride txicity, particularly where significant sil chlride levels are present. Ptassium sulfate (5) prvides a duble benefit, supplying a nutrient sulfur which is ccasinally deficient as well as ptassium, and having an anin (S4=) which is nt txic even when applied at very high rates. n respnse t the fertilizer industry's interest in imprving alfalfa frage quality, a field experiment was initiated in the winter f 1995 in Stanislaus Cunty. The site was selected because f the rather lw, 45 ppm ammnium acetate extractable sil ptassium level. The grwer was asked t withhld any applicatin f ptassium frm part f an irrigatin check and the fllwing fertilizer treatments were applied in a randmized cmplete blck design with 3 replicatins. The individual plt size was 15 feet by 25 feet with the experiment cnsisting f 54 individual plts (3 X 18). F ertilizer Rate futrient Applicatin, bs/ A 1. Cntrl 2. Ptassium Chlride 3. Ptassium Chlride 4. Ptassium Chlride 5. Ptassium Chlride 6. Ptassium Chlride 7. Ptassium Sulfate 8. Ptassium Sulfate 9. Ptassium Sulfate 1. Ptassium Sulfate 11. Ptassium Sulfate 12. Ptassium Chlride+Gypsum 13. Ptassium Chlride+Gypsum 14. Ptassium Chlride+Gypsum 15. Ptassium Chlride+Gypsum 16. Ptassium Chlride+Gypsum 17. Lime 18. Lime+Ptassium Chlride+Gypsum P2S K2 S C Lime tns tns t shuld be pinted ut at the nset that the results being presented are frm the first year nly and that final cnclusins cannt be drawn until the cmpletin f the study. Alfalfa yields were detemtined fr the 7 harvests n a 1% dry matter (DM) basis and the results fr the April111h and August 71h cuttings are given in Figures 14. Ttal yields fr the 7 harvests are given in Figures 56. Even thugh the sil tests wuld indicate a ptassium respnse might be expected, there were n statistically significant yield 128

3 increases ver the cntrl. The August 7th harvest data are presented because a visual increase in alfalfa plant height was bserved in ne replicatin frm the 8 bsl A rate f ptassium sulfate. This bservatin was nt cnsistent acrss all replicatins, thus n statistically significant yield increase was recrded in the experiment. t is difficult t explain the reductin in the seasn lng yield fr the lime treatment. t can be nted in Figure 1 that the ptassium cwride reduced the alfalfa yield at the 8 lbs K2 per acre rate. Visible damage t the alfalfa plants was bserved at the initiatin f grwth in the spring in all f the plts receiving the 8 lbs K2/ A rate f ptassium cwride. There was little r n detrimental effect in the secnd and later harvests frm the high rates. f ptassium cwride. Figures 712 present the alfalfa ttal digestible nutrient (m) data fr the April 11 h, June 121h and August 71h harvest dates. There was n statistically significant difference between the m values in the alfalfa frage fr the first 5 harvests where the tw ptassium fertilizer surces ptassium chlride and ptassium sulfate were applied. Bth Figure 9 and 11 shw the trend fr higher rates f ptassium additins t reduce the m values but this was nt bserved in the ther three harvest where the analyses have been cmpleted. trends fr phsphrus effects n m were bserved, but it appeared that the lwer yielding lime treatments had slightly higher TD values. The effect f ptassium fertilizer surces, phsphrus and lime n crude prtein fr the April 111h and August 71h harvests is illustrated in Figures The early harvests shw n trends r significant differences in crude prtein but by the August 7th harvest there was a significantly lwer crude prtein fr the 8 lbs K2/ A rate f bth ptassium fertilizer surces, ptassium chlride and ptassium sulfate. As mentined previusly, this is very preliminary data frm part f the first year's experimental investigatin. We lk frward t cnducting the study fr tw mre years t develp meaningful results and reach final cnclusins at this lcatin. 129

4 U1, (). ':s.c.r ;d.r:.u1 () U1 Jd.e :s.r U1U1 U1 i i ' i:s U1 U1. ' '+ i r\ tn :s\ U1r4.effi, :s 1 r4.r r4.u1 i.e () 1:S.r.r T' : i,..; : (1) U1MY'a,,.:.ui, :S...=.'...= ' C lt V/SUl.wa%Pla!A ejlejv '?, x: :9.. E "U; ;? ) a. "l' Ṇ "l' () Ea (.) tj1 tj1. ':1 )...,..j ).. U ).. c.c rt.ctj1 U tj1 tj1.c s CS)..1 :1.,..j ' tj1 tj1 c tj1 ).. ).. s ':1tJ1 rtc..tj1.,..j ' + 11'1t') rt rt.,..j \ :1)..1\ tj1m rt rt S.c :1Ur..,..j.tJ1S tj1:1tj1.,..j :1 tj1', )..tj1:1.,l ds j c.b c...: '1 +..r: 8. V /SUl 'Wa%Pla!A ejlejv 1 C, tn :9 " C!) "".. C E j "in tn (Q. Ln. V.. el V (/) ffi (3 m..r: '. C J..lU.r: (/] (/].e C J.. 'lu C (/] U! " 1U1(/] 141'. (/] U.e 141 =,iln llu.!\ U (/] 1\ CW) ' M\.,.. CX) tzj g t 5[rllllllllllllllllllllllllll V'1l). 6 "": ' (/)..(').'.:i :: g:;m ;t E.;n cn..... l)...c 'U c 1.Ctn tnu.e C '1.C tn 1 'ltn >ttn 1 1.e l!' \ tn\,lt). 6 f== :Lt) :J;:. " 1 cn = :m E j.cn (Q..9; 141 (/] lui!!.ụ. r= : d tn.i, [.. dl 1 El l. "': \ j Mtn! (/] =' '\. lui C ' tn ' 1 C '1/SUl 'Wa%Ple!A ejlej'1 v /SUl.wa%.Pla!A ejlejv.1:.1. cbrl tb J,.1 cb. rj.. 13

5 = ) c" l) l) c.. c(, \/)[!] a "1:i a. a. c( E C/). ::: B c.. (3. & % '(WG%6).Gl ellellv. > t') Et n =" '..4J "' s.ri "'.4J C4!.4J "' C.c: u fu!/j.5 fu r..!/j r...ri..c U fu r:. lllllllllllllllllll V!',"'1111W""""'jg. V, U;>, (, nfjflrr 1 v /SUl 'W%\.Ple!A e/le/lv. C) ;.Cv (/) = m E.. = g ='.;n C) U.. a. 'i" U Ul c. Ul 'P \ %i Et t,...j t,...j r. C'.ri 'tj t (J 'tj c ;j ;j t tu.c u r rn r rn r n \ \.,..f a. % '(W%6).l ejlejv cn lv. n 9.!1 (/) ) 6, (3. 131

6

7