Ecological Intensification of Corn-Based Cropping Systems Soil quality changes impact yield

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1 Ecologicl Intensifiction of Corn-Bsed Cropping Systems Soil qulity chnges impct yield D.T. Wlters, K.G. Cssmn, A. Doermnn, J. E. Specht, H.S. Yng, A. Wingeyer Deprtment of Agronomy nd Horticulture, University of Nersk, PO Box , Lincoln NE ; emil INTRODUCTION Meeting the projected glol demnd for food nd fuel from corn systems while conserving nturl resources nd improving environmentl qulity cn only e chieved y the intensifiction of existing corn systems (Cssmn, 1999; Cssmn et l., 2003). Since 1999 we hve een experimenting with optimizing corn mngement systems to exploit corn yield potentil. To dte, our experience hs shown tht considerle yield increses re relized y choosing the right comintion of dpted vrieties, plnting dte nd plnt popultions to mximize crop productivity. In ddition, more intensive N mngement strtegies tht focus oth on improving crop N use efficiency nd residue cron mngement lso contriute to reducing nitrogen input over the longer-term through increses in soil orgnic mtter nd N storge tht cn increse the indigenous soil N supply cpcity. Significnt increses in soil orgnic mtter nd N storge hve resulted from intensifiction of crop mngement prctices. Intensifiction hs not cused significnt increses in the glol wrming potentil of these cropping systems (Adviento-Bore, 2007). MATERIALS AND METHODS The UNL reserch progrm on Ecologicl intensifiction of irrigted mize-sed cropping systems hs the following ojectives: (i) improve the understnding of the yield potentil of corn nd soyen nd how it is ffected y mngement, (ii) develop scientific sis for evluting yield potentil t different loctions, (ii) develop prcticl technologies for mnging intensive cropping systems t 70-80% of the yield potentil, nd (iv) conduct n integrted ssessment of productivity, profitility, input use efficiency, soil cron sequestrtion, energy nd cron udgets, nd trce gs emissions. Experimentl detils re s follows: Soil: Kenneec sil (fine-silty, mixed, mesic Cumulic Hpludoll) ph (limed to 6.0), 2.7% OM, 67 ppm Bry P1, 350 ppm extrctle K. Field experiment conducted t Lincoln, NE from 1999 through 2003 Tretments: 3x3x2 fctoril experiment conducted in split-split plot rndomized complete lock design Min-plot: Irrigted crop rottions (CC-continuous mize, CS-mize-soyen) Su-plot: Plnt popultion density (P1-33; P2-37, P3-44 0pl./cre) Mize hyrid Pioneer 33A14 (Bt) plnted in 1999 nd 2000; Pioneer 33P67 (Bt) plnted in 2001 nd 2002; Pioneer 31N28 plnted in 2003.

2 Su-su-plot: Fertilizer nutrient mngement s (M1-recommended NPK rtes for yield gol of 200 u/cre, M2-intensive NPK mngement for 300 u/cre yield gol. M1: l N/ for corn fter soyen, l N/ for corn fter corn, using UNL N recommendtions; no P nd K pplied (high soil test vlues). Nitrogen split into two pplictions (pre-plnt nd V6 stges) M2: l N/ for mize fter soyen, l N/ for mize fter mize; 92 l P 2 O 5 /, 93 l K 2 O/, 10 l S/ per crop. Nitrogen split into 4 pplictions (pre-plnt, V6, V10 nd VT stges) Nitrogen fertilizer ppliction rtes hve een mde on the sis of yield gol, spring residul soil nitrte to depth of 4 feet, orgnic mtter content nd credit for previous crop of soyen s outlined in the UNL nitrogen lgorithm (Shpiro, et l., 2001). In , the corn popultion tretment ws chnged to P1=30k/cre 2 30 rows, 30 rows nd rows. In 2007, no yields were tken s the corn crop ws tken y severe wind storm tht mde it impossile to hrvest corn to determine yield. The crop ws slvged y comine hrvest nd soil prepred for plnting in No fll ppliction of n In 2008, rottion sequences were continued, ut corn ws plnted in ll plots t popultion of 34k/cre without the ppliction of P or K (no M1 or M2 tretments). A single lnket ppliction of 50 l N/cre ws mde prior to plnting. Corn ws irrigted s in the pst nd hrvested to determine the impct of recorded chnges in soil qulity on grin yield nd nutrient uptke. Herein we will report on corn yield, N use efficiency (NUE) nd chnges in oth soil C nd N over the course of the experiment nd the residul effect of chnges in soil qulity on corn yield in RESULTS Summry of long-term results Tle 1. Crop mngement prctices nd grin yields in continuous corn (CC) nd corn/soyen rottion (CS) systems with recommended (-rec) or intensive (-int) mngement ( ). CS-Rec CS-Int CC-Rec CC-Int Yield gol (% of yield potentil) Plnt density, corn (0 pl/) N pplied to corn (l/) no. of N pplictions to corn N on corn residue in fll (l/) N pplied to soyen (l/) P & K pplictions (l/) 0 40/ /75 Avg. nnul N ppliction (l/) Rnge in corn yield (u/) Averge corn yield (u/) Averge soyen yield (u/)

3 Averge crop yields in this experiment were close to the yield potentil of soyen nd corn t this loction nd significntly higher thn the ntionl or stte verge. Corn yields were generlly in the 215 to 287 u/ rnge or within 84 to 97% of the simulted yield potentil. Corn following soyen yielded out 5 to 11% higher thn continuous corn primrily due to fewer prolems with stnd estlishment nd fewer pest nd disese prolems. Chnges in soil C, N nd indigenous soil N supply Figure 1. Hypotheticl reltionship etween corn yield (Y) nd N ppliction rte (F) for verge soil qulity nd verge yield (curve A), verge yield nd incresed soil orgnic mtter content nd ssocited indigenous N supply (curve B), nd incresed soil orgnic mtter content nd indigenous N supply with improved crop mngement to chieve greter N fertilizer efficiency t ll rtes of pplied N (curve C). Scenrios B nd C ssume n increse of 50 kg N h-1 in indigenous soil N supply from the increse in soil orgnic mtter. Insert shows the overll N use efficiency (Y/F) for ech scenrio. (From Cssmn et l., 2003). Soil orgnic mtter (SOM) contriutes to soil qulity nd ecosystem function through its influence on soil physicl stility, soil microil ctivity, nutrient storge nd relese, nd environmentl qulity. Building soil orgnic mtter requires incresing oth C nd N input to soil nd incresing SOM ecomes function of N nd C mngement through ugmented plnt productivity nd incresed return of crop residue. Since the C:N rtion of SOC is

4 reltively stle,n increse in SOC decomposition should result in greter indigenous N supply nd reduction in N fertilizer requirement (see scenrios B nd C in Figure 1). Since the strt of this experiment, lrge mounts of crop residue hve een returned to the soil in ll four mngement systems, ut with significnt differences mong them in terms of dry mtter mounts nd composition. Corn returned 75 to % more residue thn soyen, ut with much wider C/N rtio. On whole crop rottion sis, verge nnul C return with ove-ground residue incresed in the order CS-rec < CS-int (+8%) < CC-rec (+22%) < CCint (+39%), wheres residue N inputs followed the order CC-rec < CS-rec < CS-int < CC-int. (Fig. 3). Both residue C nd N input were highest in the CC-int system, exceeding the more commonly prcticed CS-rec system y 30 to 40%. Annul residue C, kg C/h/yr () d Residue C Residue N c Annul residue N, kg N/h/yr 3000 CS-rec CS-int CC-rec CC-int Figure 2. Averge nnul cron nd nitrogen input to soil in crop residues ( ). CS = corn/soyen rottion; CC = continuous corn; rec = recommended nutrient mngement; int = intensive nutrient mngement. In the intensive continuous corn systems, incorportion of lrge mounts of residue C nd N hs led to significnt uild-up of SOM over just few yers. Although corn yields nd N use efficiency were higher for the intensive corn-soyen rottion, this excellent performnce ws chieved t the cost of exploiting C nd N reserves. Our results here confirm those of recent eddy covrince studies t other sites, showing tht significnt net C losses during the soyen phse of the CS rottion prohiit gins in SOC (Verm et l., 2005; Bker nd Griffiths, 2005). These oservtions led us to conclude tht the N-credit ttriuted to cornsoyen rottions ppers to e due to mining of soil N reserves. Significnt potentil for sequestrtion of tmospheric C therefore exists in intensively mnged continuous corn systems. In the CC-int, 14% more crop residue C ws returned to the soil thn in the CC-rec tretment. 70

5 Cumultive chnge in SOC, kg C/h () SOC TSN CS-rec CS-int CC-rec CC-int Cumultive chnge in TSN, kg N/h Figure 3. Cumultive chnge in soil cron (SOC) nd soil nitrogen (TSN) fter six yers of tretment. CS = corn/soyen rottion; CC = continuous corn; rec = recommended nutrient mngement; int = intensive nutrient mngement. Soil smples collected in June 2000 nd 2006, 0-12 In 2006, surfce soil (0-12 ) ws collected from CC nd CS plots tht hd received the M1-P1 nd M2-P3 tretments. Soil ws sieved nd incuted under eroic conditions nd periodiclly leched of inorgnic N for 90d period. Figure 4 shows the elevted indigenous N supply minerlized from the CC tretment tht hd received the M2 N rte s well s posthrvest fll pplictions of N to residue prior to plowing. Indigenous N supply ws pproximtely 30% greter thn the other (rottion * fertilizer mngement) tretments. Nitrogen use efficiency Tle 2 presents the overll N lnce nd N use efficiency of the four systems. Without considertion of the chnge in soil TSN sttus, most reserchers would clculte N use efficiency s the totl mount of N in grin / N ppliction rte. One cn see tht this clcultion gives n rtificilly high N use efficiency for the CS-rec system compred to the CS-int or CC systems. It would seem more pproprite to clculte system-level N use efficiency given the mesured loss in TSN nd SOC with soyen in rottion with corn. Note tht the dditionl sequestrtion of soil N in the CC systems hs resulted in system-level N use efficiencies tht re more thn doule those determined without soil improvement s considertion. Conversely, the system level N use efficiency for the CS-rec system represented 13% decline (from 3.27 to 2.84) with considertion of soil N loss.

6 il -1 ) Cummultive minerlized N (mg N kg so Time of incution (dys) CC-M1 CC-M2 CS-M1 CS-M2 Figure 4. Cumultive minerlized nitrogen (N) in the upper 30 cm of soil fter 90d of eroic incution (60% WFPS nd 25 C). Tle 2. System level N use efficiency in continuous corn (CC) nd corn/soyen rottion (CS) systems with recommended (-rec) or intensive (-int) mngement ( ). CS-Rec CS-Int CC-Rec CC-Int Annul fertilizer N input, l N/ Annul N removl with grin, l N/ Chnge in totl soil N, 0-12, l N/ Nitrogen use efficiency l N in C+S grin / l N pplied l grin N + chnge in soil N / l N pplied Residul corn yields Corn yields illustrted in Figure 5 (upper pnel) re those resulting from N supply in response to indigenous soil supply nd the 50 l N/cre pplied to ll corn plots in In the lower pnel of Figure 5 re the levels of residul preplnt soil nitrte in the upper 12 of soil. There ws little difference in residul nitrte in the continuous corn tretments s function of previous yers tretment. In 2007, there were differentil N pplictions pplied to soyen plots nd so soil nitrte levels were quite vrile. Even so, there ws no significnt impct of soil nitrte in the CS rottion on susequent grin yield in The most slient impct of previous mngement history on residul 2008 corn yield ws the interction of rottion*

7 2008 Mize Yield (u/cre) Continuous Mize M1 M2 (Rot *Pop * Mn) P = (0.01) P1 P2 P3 Mize / Soyen P1 P2 P Spring soil NO 3, (kg N h cm) P1 P2 P3 P1 P2 P3 Previous Yer Plnt Popultion Tretment Figure 5. Upper grph: 2008 residul corn grin yield s function of previous yers plnt popultion, previous crop nd long-term fertility mngement. Corn popultion in 2008 ws 34k/cre. There ws no difference in soyen plnt popultion in For corn, previous yers plnt popultions were P1= 30k/cre, P2=37k/cre nd P3=44k/cre ( ) nd P1=30k/cre, 30 rows, nd 15 rows (2006-7). Corn received lnket N ppliction of 50 l N/cre in 2008 ut no M1 nd M2 tretment pplictions. Lower grph: Spring 2008 soil nitrte N in the upper 30 cm of soil. popultion * fertility mngement. Yields of corn fter soyen were 150% of continuous corn on verge pprently the result of elevted soil nitrte (in prt) nd lck of N immoiliztion pressure. As we hve oserved, however, the indigenous soil N supply experienced in CS rottion is the result of some degree of soil C nd N loss (Figure 3 nd Tle 2). The increse in indigenous N supply under continuous corn ws evident. Here we hve oserved significnt increses in indigenous N supply under the long-term M2 tretment with soil N sequestrtion the result of increse in C input to soil with dded N. Surprisingly, we oserved ltent soil N immoiliztion pressure resulting from long-term input of high C:N residue under the CC-M1 tretment (Figures 2 nd 5). The net effect of previous residue C nd N input (popultion) ws decline in yield of 54 u/cre from 165 to 111 u/ under pst CC-M1 tretments. Even though C inputs were significntly greter in the long-run under intensive (M2) mngement in CC (Figure 2), the sequestrtion of N nd increse in indigenous N supply ws evident in 2008 in tht yield rnged from 193 u/ under P1 history

8 to low of 171 u/ under P3 history. Therefore, n ugmented minerliztion potentil under M2 history (Figure 2) resulted in difference of 60+ u/ (Figure 5). CONCLUSIONS At time when there is growing concern out the ility to produce dequte corn to meet demnd for food, feed, nd fuel (Cssmn nd Lisk, 2007), the results from our reserch highlight severl importnt points. First, there remins lrge gp etween verge corn yields currently chieved y frmers nd the yield potentil ceiling tht cn e exploited through improved crop mngement prctices. Second, intensifiction of cropping does not necessrily increse GHG emissions nd GWP of griculturl systems provided tht crops re grown with est mngement prctices nd ner yield potentil levels, resulting in high resource use efficiency. Mnging t high yield levels cretes lrge sinks for C nd minerl N, therey providing the prerequisite for sequestering tmospheric CO 2 nd voiding lrge N 2 O emissions tht could result from inefficient utiliztion of soil or fertilizer N. Finlly, the N credit ssocited with corn soyen rottions ppers to e the result of soil N exploittion. Positive chnges in soil qulity nd sytem level resource use efficiency cn e chieved through intensifiction. Increse in C inputs to soil must lso e ccompnied y N dditions to enhnce indigenous N supply. Here we hve demonstrted positive chnges in indigenous soil N supply with intensifiction which trnslte to sustntil yield responses nd improvements in N use efficiency. References Adviento-Bore, M.A.A., M.L. Hddix, D.L. Binder, D.T. Wlters nd A. Doermnn Soil greenhouse gs fluxes nd glol wrming potentil of high-yielding mize systems. Glol Chnge Biology. 13: Bker, J.M. nd T.J. Griffiths Exmining strtegies to improve the cron lnce of corn/soyen griculture using eddy covrince nd mss lnce techniques. Agriculture nd Forest Meteorology. 128: Cssmn, K.G Ecologicl intensifiction of cerel production systems: Yield potentil, soil qulity, nd precision griculture. Proc. Ntionl Acd. Sci. (USA) 96: Cssmn, K.G., Doermnn, A., Wlters, D.T., Yng, H Meeting cerel demnd while protecting nturl resources nd improving environmentl qulity. Annu. Rev. Environ. Resour. 28: Cssmn K.G. nd Lisk A. J Food nd fuel for ll: Relistic or foolish? Biofuels Bioprod. Biorefin. 1: Verm, S.B., A. Doermnn, K. Cssmn, D. Wlters, J. Knops, T. Arkeuer, A. Suyker, G. Bur, B. Amos, H. Yng, D. Ginting, K. Hurd, A. Gitelson, E. Wlter-She Annul cron dioxide exchnge in irrigted nd rinfed mize-sed groecosystems. Agric. nd Forest Meteorology. 131:77-96