Cropping Systems for Stokes Aster*

Transcription

1 Reprinted from: Perspectives on new crops nd new uses J. Jnick (ed.), ASHS Press, Alexndri, VA. Cropping Systems for Stokes Aster Elizbeth J. Clln nd Chrles W. Kennedy Stokes ster (Stokesi levis L., Composite) hs the potentil to become n industril oilseed crop for epoxy cid, compound widely used in the chemicl industry. Its chenes contin vernolic cid (12, 13- epoxy-cis-9-octdecenoic cid), which is esily converted to epoxy cid (Cmpbell 1981). One obstcle to the development of Stokes ster into crop is the fct tht the perennil does not flower during its first yer of growth (Cmpbell 1981, 1984). Spring seeded plnts will not flower tht summer nd fll seeded plnts will not flower the following summer. To overcome this economiclly unproductive first seson, Stokes ster could be intercropped with summer nnul such s soyben [Glycine mx (L.) Merr., Fbcee]. Blsbrmnin nd Sekynge (199) indicted tht intercropping prolongs the exploittion of resources due to longer combined lef re durtion. Thus, intercropping cn mke better use of lnd re by overlpping the time needed in the field by the two crops. The min benefit of soyben Stokes ster intercrop would be the initil soyben yield during the first yer of Stokes ster growth. Soyben would be the overstory crop in this system, substntilly reducing the mount of light vilble for Stokes ster seedling growth. Lrcher (1983) hs indicted tht plnts do dpt to chnges in light intensity over time s new tissue nd orgns form. In growth chmber nd greenhouse studies, we hve found tht Stokes ster growth cn be reduced by low light intensity, but djustments in photosynthesis occurred nd plnts begn recovering fter shde ws removed (Clln nd Kennedy 1995, 1996). Once recovered, Stokes ster should grow nd produce normlly through the length of the production cycle lthough no field reserch hs been conducted to corroborte this. Moreover, the length of the production cycle is somewht vgue, but estimted t 3 5 yers (Cmpbell 1981). Becuse of this lck of extensive field dt, our objectives were twofold. The first ws to determine vegettive growth nd seed yield of Stokes ster under three cropping systems ( spring-plnted monocrop, fll-plnted monocrop, nd spring-plnted intercrop with soyben). The second ws to determine the chnge in yield over severl yer period to identify vible production cycle. METHODOLOGY Plntings were initited in through 1994 t Bton Rouge, Louisin (3 N Lt.) on Mhoon silty cly lom (fine-silty, mixed, noncid, thermic, typic Fluvquent). Pioneer 951 soyben ws plnted My 1,, April 13,, nd April 23, 1994 on 76.2 cm row spcing. Due to limited seed supply coupled with vribility in germintion nd emergence of the seed, Stokes ster seed of USDA ccession BSLE2 nd n unknown prent (BSLE2, BSLE1, BSLL1, or BSLL2) were initilly germinted in germintion pper, trnsferred to 5 cm-wide pet pots filled with Jiffy mix nd trnsplnted to the field bout 1 month lter. The entire process ws initited t the time of soyben plnting so the growth of Stokes ster would be on the sme time frme s soyben, i.e., it simulted field plnting of Stokes ster. Ech intercrop plot consisted of 4 soyben rows. Three 19 cm-wide rows of Stokes ster were plnted in ech of the 3 middles between ech row of soyben. The spring-plnted monocrop contined 5 rows of Stokes ster. Row width ws 19 cm. The fllplnted monocrop of Stokes ster used the sme procedures s the spring monocrop but ws initited in erly October ech yer. All Stokes ster plots were 2.1 m long. Plot widths were.95 m for spring- nd fllplnted monocrops nd 2.28 m for the intercrop. Nutrient fertiliztion consisted of 2.9 mm N,.6 mm P,.86 mm K, 1 mm C, 1mM Mg, 1 mg/l Fe, nd 1 ml/l stock micronutrients used to wet the Jiffy mix during seedling trnsfer. For, field ppliction of 67 kg N/h ws pplied to ll spring-plnted Stokes ster plots in the lte summer nd gin in My of. The lte summer ppliction ws repeted for the plnting, but the spring ppliction occurred in lte Mrch nd ws 224 kg N/h. Therefter, only n erly spring ppliction of this mount of nitrogen ws done for ech cropping system. Soyben hrvest occurred in lte September of ech yer Stokes ster hrvest, beginning in, occurred in mid August of ech yer. Approved for publiction by the director of the Louisin Agriculturl Experiment Sttion s mnuscript

2 Weed control ws combintion of the herbicides vernolte (s-propyl dipropylcrbmothiote) nd triflurlin (2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenmine) long with hnd weeding. The use of benomyl (methyl-1-[(butylmino)crbonyl]-h-benzimidzol-2-ylcrbmte) ws used for Phomopsis blight control. Two to three pplictions of 1.12 kg/h usully provided dequte control. Plnts per m 2 nd lef number per m 2 were determined for ech cropping system during the first yer of growth. Light interception by Stokes ster under the soyben cnopy ws determined with Li-Cor 1-m line quntum sensor. The sensor ws plced prllel to the soyben row nd light intensity ws verged over 9 equidistnt positions cross the row middle t the ster lef level. This ws done 3 times t bout 3 dy intervls during the growing seson beginning bout 7 dys fter plnting. Monocropped nd intercropped soyben yields were determined on 2, 2-m lengths of row (3.5 m 2 ). Stokes ster yield ws determined from 1 m 2 hrvested re in the center prt of ech plot. The experimentl design ws rndomized complete block with 4 replictions in nd nd 3 replictions in Sttisticl nlysis ws conducted using the generl liner model technique nd men seprtion used the lest squre mens method (SAS 1985). RESULTS AND DISCUSSION Vegettive Growth In perennil-nnul intercrop, the gol is n cceptble growth rte for the perennil nd good yield for the nnul (Vndermeer 1989). Initil Stokes ster growth vried between plnting yer nd cropping system. In, seedling mortlity ws fctor in growth per unit lnd re s mesured by lef production. The soyben provided shded understory tht undoubtedly reduced soil evportion nd surfce tempertures s well s light intensity. This condition resulted in better ster seedling survivl thn in exposed monocrop plots (Fig. 1) which kept lef production per m 2 higher in the intercropping system (Fig. 2). However, lef development per plnt ws lower under the intercropped soyben cnopy (dt not shown). In nd 1994, the negtive effects of being the understory component of n intercrop ws pprent for Stokes ster. Seedling mortlity ws less of problem in the monocrop but tended to decline in the intercrop s did lef production (Fig. 1, 2). Previous work (Clln nd Kennedy 1995) hs shown tht Stokes ster cn tolerte low light intensity of t lest 16 µmol/m 2 /s photosynthetic photon flux density (PPFD) nd continue to grow, lthough slowly. At PPFD less thn 4 µmol/m 2 /s Stokes ster lef development becomes sttic nd recovery is slow (Clln nd Kennedy 1996). Although verge mid-dy PPFD reching Stokes ster ws usully t or bove bout 16 µmol/m 2 /s in the field (Fig. 3), the distribution of light would vry with loction of Stokes ster plnts reltive to the soyben row nd lso time of dy. Thus, the totl mount of light received ws probbly lower thn the verge would indicte. Moreover, the gretest decline in growth of Stokes ster during the intercropping period in ws lte in soyben development nd corresponded to the time of soyben lef drop. These senesced leves covered the Stokes ster resulting in incresed mor- Plnts/m Fll monocrop Fig. 1. Plnt popultion of Stokes ster under different cropping systems. Symbols subtended by t given time re significntly different from the spring monocrop Dys fter plnting soyben 263

3 Leves/m Fll monocrop Fig. 2. Effect of cropping system on lef development of Stokes ster. Symbols subtended by t given time re significntly different from the spring monocrop. Dys fter plnting soyben Micromoles/m2/sec Yield (kg/h) Dys fter plnting soyben Fig. 3. Photosynthetic photon flux density reching stokes ster intercropped under soyben cnopy. 5 Monocrop b 1994 Yer Fig. 4. Yields of monocropped soyben nd soyben intercropped with Stokes ster. Brs hving the sme letter for given yer re not significntly different. tlity nd lef die-bck. Becuse the popultion rebounded fter decline, the mortlity pplied only to the bove ground portion of the plnt; the growing point remined vible in mny ded plnts. Regrdless of performnce under the soyben cnopy, Stokes ster incresed in growth fter the cnopy ws removed (Fig. 2). This growth, coupled with plnt ge ws enough to llow reproductive development the following spring. The fll-plnted monocrop grew throughout its first yer, but ws too young nd/or too smll to be generlly receptive to stimuli tht cused shift to reproductive growth during the first spring subsequent to plnting. 264

4 Seed Yield Soyben yields were generlly unffected by Stokes ster s n intercrop (Fig. 4). Since Stokes ster growth ws smll during the first 6 months, its effect on soyben ws negligible. The effect of environment mong yers ws not significnt on seed yield of Stokes ster, but yers in production from initil estblishment did hve significnt impct on seed yield. For this reson, dt from ech estblishment (plnting) yer ws pooled cross production yer for nlysis. The effect of intercropping Stokes ster nd the vegettive growth decline during the period in which it ws under the soyben cnopy did tend to depress ster seed yields in the first yer following estblishment. The second yer hrvest lwys hd the gretest verge seed yield for the Stokes ster originlly intercropped (Fig. 5). Differences between spring-plnted monocrop nd intercropped Stokes ster yields (Fig. 5) my be for the resons lredy lluded nd lso becuse 25% of the lnd re ws not plnted to Stokes ster in the intercrop. On n re-plnted bsis, the intercropped Stokes ster verged higher yields thn the monocrop (dt not shown). Estblishing Stokes ster in the fll resulted in n estblishment durtion of n dditionl seven months prior to blooming compred to the other cropping systems. This prolonged durtion my hve ttributed to the slightly lower yields of tht system (Fig. 5) Yers in production from initil plnting Fig. 5. The effect of cropping system nd yers in production from the initil plnting on seed yield of Stokes ster. Averge of three plnting yers. Error brs represent stndrd error of the men. Yields of intercropped Stokes ster reflect the 25% of lnd not ctully plnted, i.e., the old soyben rows. Although seed yield of Stokes ster hs been estimted t bout 2 kg/h nd production cycle of 3 to 5 yers, (Cmpbell 1981), we did not find either to be the cse in our study. Mximum yields were generlly less thn 1 kg/h. Moreover, mximum yields did not extend pst one yer of production (Fig. 5). The yield potentil of Stokes ster t this loction my hve been lower due to soil type or some other limiting unknown fctor. The limittion of the production cycle of this perennil crop ws primrily problem of sustined weed control, Phomopsis blight, nd fire nt mound building. Although some reserch hs been conducted on tolernce of Stokes ster to vrious herbicides ( Cmpbell 1981; Clln nd Kennedy 1995b) the bility to control some weed species, especilly perennil clover species (Trifolium spp.) within n estblished Stokes ster plnting is lcking. This weed encrochment ws probbly mplified due to the smll plot sizes in this study. Phomopsis blight nd possibly other diseses reduced the plnt stnd over time, but these diseses were usully kept in check with fungicide pplictions. Mound building by fire nts (Solenopsis sevissim) smothered estblished plnts. We perceived greter number of lrge fire nt mounds in Stokes ster plots thn in the surrounding re, but hve not substntited this with dt nd the use of smll plots my hve mplified the negtive effect. Regrdless, ppliction of insecticide cn reduce this problem. CONCLUSIONS The use of n intercropping system to supplement lnd productivity during Stokes ster s estblishment yer ppers vible. However, extremely dense overstory cnopies nd subsequent lrge mount of lef drop might limit the success of intercropped Stokes ster. Mximum yield potentil t our loction ws less thn 1 kg/h nd vible production cycle could lst no more thn two yers. If Stokes ster is to become vible industril oilseed crop, dditionl efforts in breeding, nd herbicide-biotechnology need to be undertken. Seed yield (kg/h) Fll monocrop 265

5 REFERENCES Blsurbrmnin, V. nd L. Sekynge Are hrvests equivlency rtio for mesuring efficiency in multiseson intercropping. Agron. J. 82: Clln, E.J. nd C.W. Kennedy ping Stokes ster: Seedling growth under soyben cnopy. p In J. Jnick (ed.), Progress in new crops. ASHS Press, Alexndri, VA. Clln, E. J. nd C.W. Kennedy ping Stokes ster: Effect of shde on photosynthesis nd plnt morphology. Crop Sci. 35: Clln, E.J. nd C.W. Kennedy. 1995b. Tolernce of Stokes ster to selected herbicides. Indust. Crops Prod. 4: Cmpbell, T.A Responses of Stokes ster chenes to chilling. J. Am. Soc. Hort. Sci. 19: Cmpbell, T.A Agronomic potentil of Stokes ster. Am. Oil Chem. Soc. 9: Lrcher, W Physiologicl plnt ecology. Springer Verlg, New York. SAS Institute, Inc SAS User s guide: Sttistics. SAS Institute, Cry, NC. Vndermeer, J The ecology of intercropping. Cmbridge Press, New York. 266