Journal American Society of Sugar Cane Technologists, Vol. 31, 2011

Transcription

1 EFFECTS OF RESIDUE MANAGEMENT ON YIELD AFTER THREE PRODUCTION CYCLES OF A LONG-TERM SUGARCANE FIELD TRIAL IN LOUISIANA H.P. Viator 1* and J.J. Wang 2 1 LSUAgCenter, Iberia Research Station, 603 LSU Bridge Rd., Jeanerette, LA LSUAgCenter, School of Plant, Environmental and Soil Sciences, 104 M. B. Sturgis, Louisiana State University (LSU), Baton Rouge, LA *Corresponding author: sviator@agctr.lsu.edu ABSTRACT A study to evaluate the long-term effects of post-harvest crop residue management on the yield of sugarcane, Saccharum spp. hybrids, grown on silty clay loam (Vertic Haplaquoll) was initiated in 1996 and continued for three production cycles, a total of 10 crops. The debilitating effects on ratoon crops of residue retention are well documented, but the cumulative effects across production cycles have not been quantified in Louisiana s temperate, humid environment. Residue management treatments included: 1) pre-harvest burning (B); 2) post-harvest residue swept to the row furrows (S); and 3) full retention of the residue (R). Retaining the residue resulted in numerical reductions for yield, stalk population and theoretical recoverable sucrose (TRS), but only reductions in cane and sugar yield were statistically significant. Burning, B, resulted in an average sugar yield increase of 0.96 Mg ha -1 over R and 0.64 Mg ha -1 over S. This study clearly demonstrated the temporal nature of the influence on yield of residue retention, as yield reductions from non removal of crop residue were confined to ratoon crops within a production cycle and the negative effects did not carryover to the plant-cane crops of subsequent cycles. Keywords: sugarcane; pre-harvest burning; post-harvest residue management; long-term basis INTRODUCTION With the advent of the chopper harvester in the early 1990s, Louisiana sugarcane growers were at a disadvantage in knowing whether to burn standing prior to harvest, to green-cane harvest with post-harvest burning of the residue, or to retain the residue (trash blanketing). Information confirming the negative effects of green cane trash blanketing was limited (Seeruttun et al. 1992; Wiedenfeld 1985). Certainly, the long-term consequences of their residue management choices were unknown. Harvest residue retention is practiced in the tropical, arid sugarcane growing regions and has been particularly beneficial on a long-term basis (Thompson 1966; Graham et al. 1999; Van Antwerpen et al. 2001). Guidance, however, from other sugarcane production areas of the world (Monzon 1956; Torres and Villegas 1995) was not helpful because of the unique temperature and moisture regimes of Louisiana. Where wet, cool conditions persist, retention of post-harvest residues can attenuate cane yields in the ratoon crops (Bell et al. 1999; Richard 2001; Viator et al. 2005, 2006 and 2009b). Pre-harvest burning was popular initially but gave way to post-harvest burning of the residue on the soil surface when 15

2 Viator and Wang: Long Term Residue Management issues of liability for damages surfaced. Post-harvest burning results in less smoke and soot so now the majority of the acreage is post-harvest burned. The purpose of this paper is to summarize the effects of residue management over three production cycles (10 crop years/2 fallow periods) on the cane and sugar yields under Louisiana growing conditions. Of particular interest is the determination of possible cumulative effects on yield as the production cycles advance. If it is discovered that residue management approaches affect resultant yields differentially, then growers will have a clearer appreciation of options to achieve highest yield. MATERIALS AND METHODS The sugarcane cultivar LCP (Milligan et al. 1994) was planted on a silty clay loam (Vertic Haplaquoll) at Jeanerette, LA (29º N, 91º W) in the fall of Mean annual rainfall and mean low temperature for January through March, the period immediately preceding emergence, for this site were 1,524 mm and 7.8º C, respectively. Randomized in a replicated complete block design were the following residue management treatments: 1) pre-harvest burning (B), 2) post-harvest residue swept to the row furrows (S) and 3) full retention of the residue (R). The pre-harvest burning treatment plots, B, and the residueretained treatment plots, R, were established initially with the plant-cane harvest in the first production cycle on December 10, Subsequent harvest dates were 18 November 1998, 07 October 1999 and 20 October 2000 for cycle one; 22 November 2002, 08 October 2003 and 15 October 2004 for cycle two; and 09 January 2007, 29 October 2007, 30 October 2008 and 05 November 2009 for cycle three. The S treatment was subsequently imposed within a two-week period on plots with post-harvest residue by mechanically sweeping the residue to the furrow bottoms, except when delayed by wet field conditions. Residue management treatments were similar for each subsequent crop in three production cycles, with plots maintained in place for a total of eight ratoon harvests. The number of ratoon crops harvested for cycles 1, 2, and 3 were 3, 2, and 3, respectively. Sugarcane cultivar LCP was replanted for production cycle 2, but HoCP (Tew et al. 2005) was planted for the third production cycle. Plot dimensions were 6 rows, 1.8 m wide by 120 m long, sufficient size to ensure a uniform and realistic distribution of residue. LSU AgCenter recommendations for cultural and fertilizer practices were followed (Legendre 2001; Johnson et al. 2008). Comparisons were made for post-harvest residue dry matter (Mg ha -1 ) remaining in the field, TRS (g kg -1 ), stalk population (stalks ha -1 ), cane yield (Mg ha -1 ) and sugar yield (Mg ha -1 ). The amount of post-harvest residue was estimated by random sampling of three 1 m 2 sections from row tops in both burned and unburned plots. Dry matter weight was calculated after the oven-dried (50º C) residue had reached constant weight. Cane yield was determined by harvesting with a single-row combine (Various Models, John Deere, Thibodeaux, LA, USA) each plot row and weighing with a weigh wagon instrumented with electronic load cells. Ten-stalk samples were used to determine TRS levels. Different methods were used to analyze for juice quality in this experiment. Prior to 2007, juice was extracted using a 3-roller sample mill. Brix was measured with a Model RFM110 Bellingham & Stanley Refractometer (Lawrenceville, GA) and pol was measured using an Autopol 880 Rudolph Research Saccharimeter (Flanders, NJ). Beginning in 2007, stalks were shredded by a Dedini shredder and scanned using a Spectracane 200 NIR (Lower Hutt, New Zealand). Comparison of the methods resulted in an R 2 value for Brix of 0.96 and for Pol (Zº) of 16

3 0.93 (K. Gravois, pers. comm., February 21, 2011). Sugar yield was estimated as the product of cane yield and TRS. Cane and sugar yield, TRS, stalk population, and dry matter residue data were analyzed with the Proc Mixed procedure (SAS v 9.1), with the analysis using crop in the cycle as repeated measures. Replication was considered a random effect and year and residue treatment were considered fixed effects. The covariance structure selected to describe repeated measures covariance for the dependent variables was the autoregressive model. The autoregressive model factors in the influence of the variances of previous crop s error terms on the subsequent ratoon crop s error term variance. The appropriateness of this model was demonstrated by Kimbeng et al. (2009), who observed that correlations among crops within a production cycle were generally higher within the same locations than across locations and crops of close proximity compared to crops of far proximity. Means for variables with significant F ratios were separated using the PDIFF option at the P=5% level. RESULTS AND DISCUSSION Post-harvest Residue Data The analysis of variance (Table 1) revealed that the quantity of post-harvest residue differed (P<.0001) between residue management treatments and the treatment x year interaction was significant (P=.0003). The treatment x year interaction was a result of differences in magnitude and not a reversal in ranking for residue dry matter means and, therefore, observations concerning treatment effects are made as an average of all years. Post-harvest residue amounts are shown in Table 2. The average amount of residue remaining after harvest was 5.88 and Mg ha -1, respectively, for B and R. Residue deposition was numerically greater for R compared to B across years. The amount of residue remaining after pre-harvest burning in certain years was surprising. Note that for both the first ratoon crop of cycle 2 and the plantcane crop of cycle 3 high amounts of post-harvest residue remained for B. Such biomass residuals undoubtedly resulted in lowering subsequent yield. Relative yield comparison, however, revealed that B plots had greater sugar yield than the residue-retained treatment (see next section on yield data). Agronomic Data Stalk population (P=.3063) was not significantly affected by residue management treatments (Table 3). Comparing stalk number, however, as an average of the last ratoon crop in each production cycle for B (120,760 stalks ha -1 ) and R (108,511 stalks ha -1 ) revealed a pronounced disparity. Without exception, R plots of the final ratoon crop in each production cycle possessed numerically lower stalk populations than the other two residue management treatments (data not shown in tabular form). Monzon (1956) observed fewer tillers with residue retention and Viator et al. (2009b) showed lower populations if residue was not removed before winter dormancy. Retaining the residue in Louisiana s humid, temperate environment affects emergence and tillering (Viator et al. 2005) when soil conditions are cool and wet. Seeruttun et al. (1992) also measured cooler temperatures (3º C) under a green cane trash blanket. Viator et al. (2006) established under greenhouse conditions that post-harvest residue showed allelopathic, 17

4 Viator and Wang: Long Term Residue Management autotoxic, and hormetic properties and allelochemicals were isolated in sugarcane residue by Sampietro et.al. (2006). In the tropics, the effects of trash blanketing on tillering are transitory and can be compensated for in the longer growing seasons (Torres and Villegas 1995). TRS (P=.2278) exhibited an indifferent response to residue management (Table 3). It must be acknowledged, however, that differences in response between the burned and nonburned treatments must factor in the direct effects of burning prior to harvesting as well as the effects of the retained residue, except, of course, for the plant-cane crops grown after a conventional fallow period. Wiedenfeld (2009) reported higher cane sucrose for plant-cane that was pre-harvest burned and suggested that the higher sucrose recovery was due to harvest efficiency. In an unpublished study (B. Legendre, pers. comm., June 10, 2010) it was found that pre-harvest burned stalks averaged 3 g kg -1 less sugar than stalks from which the trash was stripped prior to harvest. American Sugar Cane League of the U.S.A., Inc. agronomists (W. Jackson, pers. comm., October 6, 2010) conducted several studies to compare the yield and quality resulting from combine harvest of green cane and pre-harvest burned cane. They observed that differences in TRS were inconsistent, and that proper combine setting, throughput rate and operating speed could serve to minimize quality differences between green and preharvest burned cane. Similarly, Gomez et al. (2006) showed losses in sugar from pre-harvest burning of plant cane, but such losses were generally made up by losses in green cane harvesting from trash not removed by combine extractor fans. Sugar yield (P=.0002) and cane yield (P=.0072) were influenced by residue management treatments (Table 1). Sugar yield for B was significantly higher than for R and S, as an average of all crops across the three production cycles (Table 4). Burning resulted in an average sugar yield increase of 0.96 Mg ha -1 greater than R and 0.64 Mg ha -1 greater than S. The yield of cane for B was significantly higher than for the other two residue management treatments (Table 3), which were not significantly different. In keeping with reports from Louisiana in the literature (Bengston and Selim 2006; Richard 2001; Viator et al. 2005, 2006, 2009a and 2009b) residue retention in this study adversely affected ratoon crops. The results here contrast with that of the Mount Edgecombe long-term residue management study in South Africa (Van Antwerpen 2001) In that study, conducted in a tropical, arid growing environment, green cane harvesting produced a significant yield benefit, presumably from higher rainfall efficiency, reduced weed competition, and favorable soil properties such as moisture retention, nutrients recycling and organic matter. It was reported that green cane harvesting produced, on the average, 8.16 Mg ha -1 yr -1 of cane more than the conventional practice of pre-harvest burning in South Africa, approximately the same magnitude (7.4 Mg ha -1 ) of loss associated with green cane harvesting in this study. The possibility that the negative effects of trash blanketing might be cumulative across production cycles is not documented in the literature for temperate, humid environments. Though the treatment x year interaction was not significant for sugar yield (Table 1), plant-cane sugar yield for R to begin production cycle three, Mg ha -1 (Table 4) was numerically among the highest treatment mean yields recorded in the study. Likewise, the plant cane yield for R in cycle two, 7.23 Mg ha -1, was the numerically highest yield for all of the R means in cycle two. The occurrence of such high yields for plant cane as the production cycles advance 18

5 demonstrates that the negative effects of residue retention are temporal and do not carryover from one production cycle to the subsequent one. Perhaps this should have been intuitive and has been observed anecdotally, but nevertheless it confirms the fallow period s capability of not only rejuvenating the soil but also of providing a growing environment at the beginning of the next production cycle unaffected by the debilitating influence of post-harvest residue generated during harvest of the last ratoon crop of the previous production cycle. While no carryover effects were detected for yield, it is likely the soil conditions were altered by the nutritional value contained in the retained residue. Numerous investigators have measured or modeled soil enrichment for green cane harvesting on both a long-term basis (Graham et al. 1999; Graham et al. 2002; Van Antwerpen, et al. 2001; Razafimbelo et.al. 2006) and even on a short-term basis (Ball-Coelho et al. 1993; Wiedenfeld 2009). Plant and soil sampling was accomplished for this investigation to determine nutritional effects, the results of which will be the subject of a follow up article. CONCLUSIONS Residue retention in Louisiana s cool, wet climate, typically prevailing during crop emergence, causes damaging conditions that have potential to undermine crop establishment in the spring. This contrasts with tropical, arid sugarcane growing regions where yield benefits are observed from post-harvest residue retention. This study has confirmed what other investigations have found, that post-harvest residue generated from green cane harvesting under Louisiana conditions has a negative effect on the cane and sugar yield of ratoon crops within a production cycle, with resultant yield for B higher than R and yield for S generally intermediate. A primary objective of the study was the concern that the retained residue would have a cumulative adverse effect across production cycles. Fortunately, this did not materialize, as yield recovery was evident in the plant-cane crops of cycles two and three. The fallow period, vigorous commercial varieties, and associated cultural practices appear to play a role in mitigating the harmful effects of the trash blanket and provides a restorative effect on plant-cane crops at the initiation of each production cycle. ACKNOWLEDGEMENTS The authors would like to acknowledge the assistance of Greg Williams and Gert Hawkins, who were singularly instrumental in the conduct of research. Sustained support from the American Sugar Cane League of the U.S.A., Inc. made possible such a long-term study. 19

6 Viator and Wang: Long Term Residue Management REFERENCES Ball-Coelho, B., H. Tiessen, J.W.B. Stewart, I.H. Salcedo, and E.V.S.B. Sampaio Residue management effects on sugarcane yield and soil properties in Northeastern Brazil. Agron. J. 85: Bell, M.J., Halpin, N. Cunningham, G. Garside, A.L. and Kingston, G Effects of wet soil during early season ratoon establishment on sugarcane grown under different trash management systems in southern canelands. Proc. Aust. Soc. Sugar Cane Technol. 21: Bengtson, R.L. and H. M. Selim Impact of sugarcane management strategies on water quality and crop yield. ASABE paper No St. Joseph, Mich. ASABE. Gomez, J., D. Chapple and L. McDonald Sugar losses in burnt and green cane harvesting in Argentina. SRDC Report on Project CSR032:1-8. Graham, M.H., R. J. Haynes and J.H. Meyer, Green cane harvesting promotes accumulation of soil organic matter and an improvement in soil health. Proc. S. Afr. Sug. Technol. Ass. 73: Graham, M. H., R.J. Haynes and R.J. Meyer Soil organic matter content and quality: effects of fertilizer applications, burning and trash retention on a long-term sugarcane experiment in South Africa. Soil Biol. Biochem. 34: Johnson, R., H. Viator and B. Legendre Sugarcane fertilizer recommendations for the 2008 crop year. Sugar Bulletin 86(6):11. Kimbeng, C. A., M. M. Zhou and J. A. da Silva Genotype x environment interactions and resource allocation in sugarcane yield trials in the Rio Grande Valley Region of Texas. J. Amer. Soc. of Sugar Cane Technol: 29: Legendre, B.L Sugarcane Production Handbook. Pub La. St. Univ. Ag. Cen., La. Agri. Exp. Sta., La. Coop. Ext. Ser., Baton Rouge, LA. 52pp. Milligan, S.B., F.A. Martin, K.P. Bischoff, J.P. Quebedeaux, E.O. Dufrene, K.L. Quebedeaux, J.W. Hoy, T.E. Reagan, and B.L. Legendre Registration of LCP sugarcane. Crop Sci. 34(3): Monzon, F.A Queima da cana. Solo 48: Razafimbelo, T., B. Barthes, M. Larre-Larrouy, E. De Luca, J. Laurent. C. Cerri and C. Feller Effect of sugarcane residue management (mulching versus burning) on organic matter in a clayey Oxisol from southern Brazil. Agric., Ecosyst. And Envir. 115:

7 Richard, E.P., Jr Management of chopper harvester-generated green cane trash blanket: A new concern for Louisiana. Proc. Inter. Soc. Sugar Cane Technol. 23(2): Sampietro, D.A., M.A. Vattuone, and M.I. Isla Plant growth inhibitors isolated from sugarcane (Saccharum officinarum) straw. J. Plant Physiol. 163: Seeruttun, S., G. McIntyre, and C. Barbe Agronomic and economic significance of trash blanketing in the sub-humid areas of Mauritius. Revue Agricole Et sucriere DeL, ile Maurice. 71: Tew, T.L., W.H. White, B.L. Legendre, M.P. Grisham, E.O. Dufrene, D.D. Garrison, J.C. Veremis, Y.-B. Pan, E.P. Richard, Jr., and J.D. Miller Registration of HoCP sugarcane. Crop Sci. 45: Torres, J., and F. Villegas Green cane management under heavy trash conditions. Proc. Int. Soc. Sugarcane Technol. 22: Thompson, G. D The production of trash and its effects as a mulch on the soil and on sugarcane nutrition. Proc. S. Afr. Sug. Technol. Ass. 40: Van Antwerpen, R., Meyer, J. H. and Turner, P.E.T The effects of cane trash on yield and nutrition from the long-term field trial at Mount Edgecombe. Proc. S. Afr. Sug. Technol. Ass. 75: Viator, H. P., J. W. Flanagan, L. A.Gaston, S. G.Hall, J. W. Hoy, T. M. Hymel, B. L. Legendre, J. J. Wang and M. Zhou. 2009a. The influence of post-harvest residue management on water quality and sugarcane yield in Louisiana. J. Amer. Soc. Sugar Cane Tech. 29:1-10. Viator, R., R. M. Johnson and E. Richard Challenges of post-harvest residue retention management in the Louisiana sugarcane industry. Proc. Int. Soc. Sugar Cane Technol. 25: Viator, R.P., R.M. Johnson, C.C. Grimm, and E.P. Richard, Jr Allelopathic, autotoxic, and hormetic effects of postharvest sugarcane residue. Agron. J. 98: Viator, R.P., R.M. Johnson, D.L. Boykin and E.P. Richard, Jr. 2009b. Sugarcane postharvest residue management in a temperate climate. Crop Sci. 49: Wiedenfeld, R.P., B.W. Hipp, and S.A. Reeves Effect of residue from unburned sugarcane harvest. J. Am. Soc. Sugar Cane Technol. 5: Wiedenfeld. R.P Effects of green harvesting vs burning on soil properties, growth and yield of sugarcane in south Texas. J. Am. Soc. Sugar Cane Technol. 29:

8 Viator and Wang: Long Term Residue Management Table 1. P-values for fixed effects for residue dry matter and yield parameters. Source Parameter Treatment (T) Year (Y) T*Y Residue dry matter (Mg ha -1 ) < < Sugar yield (Mg ha -1 ) < Cane yield (Mg ha -1 ) < TRS (g kg -1 ) < Population (stalks ha -1 )

9 Table 2. Sugarcane harvest-residue dry matter means (Mg ha -1 ) 1. Residue management treatment Pre-harvest burned (B) Retained (R) Cycle 1 Second ratoon 2.04 b 7.39 a Third ratoon 2.53 b 4.32 a Cycle 2 Plant-cane 5.00 b a First ratoon b a Second ratoon 6.09 a 6.97 a Cycle 3 Plant-cane b a First ratoon 5.53 b 8.02 a Second ratoon 2.73 b 6.14 a Mean 5.88 b a 1 Means in a row followed by the same letter are not significantly different (α = 0.05). There were a total of 11 crops in the 3 production cycles, but residue dry matter means are shown for only for 8 crops, as sampling for residue dry matter was initiated with the second ratoon crop of cycle 1. 23

10 Viator and Wang: Long Term Residue Management Table 3. Influence of residue management on mean 1 cane yield, sucrose content and stalk population as an average of 10 crops in three consecutive production cycles. Residue management treatment Pre-harvest Cane yield Mg ha -1 TRS g kg -1 Population Stalks ha a 105 a 121,079 a burned (B) Swept (S) 79.5 b 103 a 118,272 a Retained (R) 76.6 b 102 a 114,119 a 1 Means in a column followed by the same letter are not significantly different (α =.05) 24

11 Table 4. Influence of residue management on sugar yield in three consecutive production cycles. Residue management treatment Pre-harvest burned (B) Swept (S) Retained (R) Cycle 1 Mg ha -1 First ratoon Second ratoon Third ratoon Cycle 2 Plant-cane First ratoon Second ratoon Cycle 3 Plant-cane First ratoon Second ratoon Third ratoon Mean a 8.06 b 7.74 b 1 Means in the row followed by the same letter are not significantly different (α =.05). The year x treatment interaction was not significant but treatment yields are displayed by year to emphasize the plant-cane yield recovery in cycles 2 and 3. 25