THE EFFECT OF LATE FALL HARVEST ON ALFALFA STAND AND YIELD -A PROGRESS REPORT. Carl Schoner Farm Advisor U.C. Cooperative Extension

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1 THE EFFECT F LATE FALL HARVEST ALFALFA STAD AD YIELD A PRGRESS REPRT Carl Shoner Farm Advisor C Cooperative Extension Woodland, California ver the years, growers have frequently asked the question, what shall I do with my alfalfa in the f&ll? Shall T irrigate after the last fall utting? Shall I try for one more utting evqq tkough hanes of rainfall ar high? What about green hopping the fall growth or maybe graing it with animals? What effet will any or all of these praties have on my alfalfa? The onsensus of most researhers is that fall is a time whn alfalfa plants should have an opportunity to grow and reover from the onstant utting and trampling given them during the haying season During the fall {of t year) alfalfa plants have an opportunity to manufature food and build root reserves unhpered by frequent removal of top growth Adequate moisture whether from preipitation w irrigation is one essential element of this rebuilding proess The effet of fall utting has been studied in other states (evada for examplel/) but definite information was laking to answrrower u6stions for the Saramento Valley In 1978 a relatively simple experiment was established to nek the effet of late fall harvest on alfalfa stands and yields The test was a part of alfalfa variety yield and performane tests onduted in ooperation with Extension Agronomist Dr Vern Marble and Dr Larry Teuber Department of Agronomy Alfalfa ultivars with two distintly different growth habits were hosen for purposes of the experiment A semiwinterdormant growth type and a very nonwinterdormant growth type Semiwinterdormant alfalfas generally show little if any growth or regrowth during the months of ovember, Deember, January or February in the Saramento area onwinterdormant types initiate vigorous growth in early spring and ontinue through summer and fall, exhibiting very little dormany even during the winter season El Camino Brand WL 318 was hosen to represent a semiwinterdormant type and C hosen to represent a nonwinterdormant alfalfa type Three treatments were imposed on the two alfalfa ultivars (Table 1) Cuttings Hay Season Late rota) 1 WL 318 WL 318 A WL 318 B A B Eah treatment was repliated four times All plots were harvested six times, with a Carter harvester, during eah summer hay season Irrigations were applied after last summer harvest eah year and late harvest treatments were imposed in early ovember and early Deember eah fall {Table ) ov 1 ov 1 + De 15

2 Impat of late harvest on alfalfa hay yields was determined by measuring hay yields during sueeding hay harvest seasons Eletri hedge trimmers used for fall utting of the 51 x 14' plots allowed lose lipping, similar to animal graing Beause of this lose lipping, late harvest forage weights exeeded the amounts that woul1 have been obtained with a swather or green hopper Alfalfa regrowth the following spring previded the first observable evidene that fall harvest may be detrimental to alfalfa plants Either one or two late harvests aused delayed regrowth the following spring (Table ) Two late harvests (ovember and Deember) appeared to retard growth more than a single lte harvest (ovember) on the nonwinterdormant Treatmen! 1 Table LATE HARVEST TRIALS Spring regrowth following late fall harvests Late Harvests InhesReQrowth;3/2/79 WL 318 6" WL 318 A 1 3" WL 318 B 2 2" 1 A B 1 2 ll'i 8" " This experiment has been ontlnueo through three harvest seasons to date It is evident that harvests made in early ovember and early Deember eah year have had a detrimental effet on summer season hay yields (Figure 1) A single, late harvest in the fall of eah year redued sueeding hay yields approx imately 8 perent for both ultivars A seond late harvest redued yields of the nonwinterdormant ultivar an additional 12% but semidormant alfalfa yields dereased only 2% r: r I I ), ) I/I, 1/1 r r,, r 1/la E b (/) J t = t (/) I&J u: "C XI I '1 ", o In Ln r:,+ '+ '+ r 't:j 't:j r r r 1/1 '+ r I/I VI s 1 s= V) +' 1 V) r f " r= : o : " VI +' f I I II) In II) 3H H3d SJ I/I r E, E u LL r : 1 16

3 () Q ", m <,\,, \" 1\,(\I \ \ 3:'V' 3d \ o: m SJ 1 1 :: u Ir r W Ertl W'I V1 rti'irtl 'Ir l l CW rrtl W r: l CW M W rti rtl V1 "CrV1 rr"c Wr '1 W rti C'I r V1rtl rti'1v1 W V1rtlC W Ea: rti I :1:rtlrtl\ EW' \ r M"C I V1 WV1C WW V1 lcrtl r:v1 rti W G) I C ) t ) a &1 'V ::), CD M) If) (\I t t ::) () r Ir I '+ M Qj 1'+ 1 '+r Qj n 1 n55 Qj, r1 Qj,n aqj, 5 I In "rln rr" Qjr, '+ Qj, 1 '+ r InI l'+ln 1 Qjr Qjr,ECX) II :I:11'\ EQjr s:5'\ r " I In 3Y:V Y3d Sl Qj 5QjQj In n51 1 Qj C1n "1],,

4 The d1fferene in y1eld redut1on between the two ultivars was attributed to differenes in their fall and winter growth habits The nonwinterdormant utilied root reserves to send out new regrowth following the ovember 1 harvest This seven inh tall regrowth was lipped in Deember and the plants attempted to regrow again in Deember The semiw1nterdormant Wl 318 had nearly eased growth by ovember and suffered little additional damage from Deember lipping Summer hay yields plotted by utting (Fig 2 & 3) tell an interesting story of summer yields are affeted by late fall harvest The major yield depression ourred at the first three uttings with both nondormant and semidormant types By fourth utting alfalfas from late harvest treatments had reovered and were yielding nearly as well as the untreated ontrols It is again evident that two late harvests had the greatest impat on the nonwinterdormant ultivar Even when forage yields from the ovember and Deember uttings were added to summer hay yields there was a disadvantage to late utting (Table 4) Alfalfa allowed to grow unhindered throughout the fall season yielded 2 to 5% more than alfalfa harvested only in early ovember and 7% to 13% more than alfalfa harvested on both dates Table 4 LATE HARVEST TRIALS Hay Season + Late Harvest Yields YieldsTons/Are Hay Season Late Harv Total WL WL 318 A 25 WL 318 B A B Alfalfa plant density {stand) ounts were made at the end of the third season {Table 5) Late harvest treatment had no effet on plant density of the semidormant WL 318 Although plant ounts of the nondormant CF show a trend toward stand redution with late harvest the differenes are not statistially signifiant This leads to the speulation that late harvests weaken plants rather thanreduing stand The result is early spring growth that is less vigorous than if plants had been allowed to restore root reserves during late fall andwinter Table 5 LATLHARVEST TRIALS Plant density ounts falls of 1981 Plants/square foot 1 WL 318 WL 318 A WL 318 B A 8 J; 2 4 A seond set of late harvest experiment was initiated in 1979 Alfalfa ultivars with slightly differentgrowth harateristiswere hosen for these tests Pioneer Brand 581 was hosen as an intermediatewinterdormant type and Ferry Morse's AS13R Brand hosen as a nonwinterdormant type As in the previous instane, this late harvest experiment was part of a larger:alfalfa variety yield trial onduted en the Agronomy Farm at C Davis 18

5 The experiment was planted in the fall of 1979 and harvested five times during the 198 summer season In the fall of 198 the experiment was irrigated and late harvest treatments imposed on the two alfalfa ultivars (Table 6) Table 6 LATE HARVEST TRIALS 198Q81 As in the previous test, retarded sprin growth was the first visual evidene that late harvest might have detrimental impat (Table 7) Table 7 LATE HARVEST TRIALS Spring regrowth following late fall harvests Lat Hry Inhes Regrowth 3/2/ AS 13R AS 13R A AS 13R B 1 2 " ; '\ & 3Y:Y Y3d Sl ; +' I I/I +' 1/1 +' +'Cr +' QlI/lo E +'+' C +, ItI Ql +' 'I r r 1/I1tl Ll') Ql ; +'+' +, 'IQl+, 'Irltl "tj+'+' "tj ItI r 1/1 '1 1/1),",,"I/I QlE Er :;,r )ItI lj ItI :: 1 I/\ 1 1 II 1 r of) II VI + C dl S 1 $ 1 /1 /1 s II 19

6 C m tn 1&1 w o C' u 3H:'t H3d S1!:7'!:7' CC r +':J: +' s '+ r :3r r '+ a '+ Vlr r'+ QlrVI r, +' C +, CCE +' VIE", QlS VI+' I s+' 'VI C+, C r r s J:J:", olc r r +'r r l'+ QlE s+' :3Q1",!:7'+'r r C u r ;D If ;' rt) (1) «q <\1 " / 4: / : \: \:, i, ' «3: Y3d SL q M') ) CD Z 1 1 C1" CC VI " ",",VI 1f VI ", C, C1 C,If 1f VI ES CX o ",ai " 1 VI S "I S C s 1 C1C LJCIf 2,

7 Regrowth measured in the spring of 1981 showed an advantage in height for alfalfa with no late harvests There was however little differene between the one and two harvest treatments As in the previous experiment, the greatest loss of hay yield ourred during the first three uttings of the following hay seaon (Figures 4,5 & 6) it is speulated that both ultivars in this test had nearly eased growth by Deember 1 and therefore were not greatly affeted by the seond lipping This is in ontrast to the very nonwinterdormant CF ll'of the previous experiment CF ontinued,tq grow slowly throughout most of the winter season and was onsiderably damaged by a seond utting in Deember It is unfortunate that an additional treatment (a single harvst on Deember 1} was not inluded in the two experiments It is likely that a single"h"arvest or graing after alfalfa plnts nave eased growth would flq! have dereased yields during the sueeding hay season Evjdene of this has been shown in niversity of evada graing tests where no loss of hay yield ourred when alfalfa plants were graed during the winter after they had eased growth What onlusions an be reahed based on 'information developed in these experiments? First onlusions must be tentative beause test results have raised additional questions onerning the number and timing of late harvests Seondly this information applies diretly only to Yolo County or a portionof the Saramento Valley neighboring Yolo County ther alfalfa growing areas may have different limati onditions harvest regimes and use varieties that may give different results For the Yolo County area, however, it is evident that a harvest in early ovember, following a six utting hay season did derease yields the sueeding year A seond harvest in Deember did or did not ause additional yield redutions depending on time of utting and dormany of the variety Finally" it is possible that a single utting or graing in Deember, after alfalfa has eased growth, may not ause redutions in sueeding hay yields, but this onjeture must be borne out by further investigations 1/ Jensen EH Skivington RR and Bohman VR Dormant Season Graing of Alfalfa February 1981,21