Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana

Transcription

1 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Magdi Selim 1*, Brenda Tubaña 1, Allen Arceneaux 1, Mustafa A. Elrashidi 2, Chris Coreil 3, and Paul M. White, Jr. 4 1 School of Plant Environm. & Soil Sci, LSU AgCenter, Baton Rouge, LA NRCS, Lincoln, NE 3 NRCS, Alexandria, LA USDA Sugarcane Research Unit, Houma, LA * Corresponding author: mselim@agcenter.lsu.edu ABSTRACT The focus of the study was to provide information on implementation of a modified postharvest crop residue sweeper on sugarcane yield and water quality. Field experiments were established at three different locations in south Louisiana: Paincourtville, Duson and Baton Rouge. In each location, large plots were selected for the following treatments, burn, mulch, and sweep. For the burn treatment, the residue was burned on the ground following sugarcane harvest, whereas for the mulch treatment the residue was not removed from the surface. For the sweep treatment, a modified sweeper was used following harvest. The sweeper removed the residue from the top of the mulch to the furrows. Sugarcane yield was collected at harvest and subsamples were processed for sucrose analysis. To monitor water quality, selected sites were instrumented with water samplers, flow modules, area velocity meters, rain gauges, and 45-cm H-type flumes. Our results indicated that there were no significant differences observed for the total soil loss (dissolved and total solids), turbidity, phosphorus and nitrogen among the three treatments. In fact, the influence of the sweeper on soil and nutrient losses were comparable to runoff from burn and mulch management strategies. Moreover, sugarcane yields were not significantly different from mulch or burn treatments. This finding was based on results from five growing seasons ( ) and 5 different farms at the 3 locations. Keywords: Tillage, water quality, sweeper, yield INTRODUCTION The effect of surface crop residues on interception, subsequent wash-off, and movement of herbicide in the soil profile is a primary focus associated with conservation measures in today s agricultural landscape. Various forms of soil conservation are highly recommended in an effort to reduce soil losses and runoff of applied agricultural chemicals. Conservation production systems are characterized by the presence of mulch residue left on the soil surface to protect it from water and soil erosion. Therefore, there is considerable interest in the impact of the sugarcane residue or mulch cover on reducing sediment and nutrient losses, particularly nitrogen (N) and phosphorus (P). Not 1

2 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana surprisingly, economics also drives conservation practice development. Deliberto et al (2016) estimates annual ratoon production direct expenses of $ and $53.35 ha -1 for mineral N and P, respectively. The annual costs of soil-applied residual herbicides can be up to $20.75, $49.97, and $13.44 ha -1, respectively, for metribuzin, pendimethalin, and 2,4-D/dicamba formulations. Numerous studies on several crops have shown that crop residue or surface mulch can enhance control of weeds and in reducing herbicide losses. This information is essential for the implementation of control measures or corrective actions needed to reduce chemical and sediment losses from crop lands and thus reduce contamination of surface and subsurface waters while maximizing their effectiveness for cane production. Selim et al. (2003) evaluated the effectiveness of sugarcane mulch residue on the retention of applied herbicides as well as losses in runoff. They reported that significant amounts of applied herbicides were intercepted by the sugarcane mulch residue and thus retained in the field. In the mid-1990s, the sugarcane industry in Louisiana and elsewhere adopted a new harvesting technology which involves the use of a combine harvester that cuts the cane stalks into billets, which are directly loaded into wagons for transport to the mill. Extractor fans in the combine separate extraneous leaf material and stalk tops from billets and deposit the plant residue on the soil surface. Historically, the sugarcane residue has been removed by burning. In Louisiana, a major economic concern is the impact of the presence of residue on sugarcane yield. Richard (1999) and Richard and Johnson (2003) reported reductions in subsequent sugar yields when the sugarcane residue was not removed. Burning the residue prior to or following harvest reduces the impact of the residue on crop emergence in the spring and ultimately sugar yield. In fact, Viator et al. (2009) and Viator and Wang (2011) reported that based on several studies, sugar yields in plots where residue was burned were higher than (a) when the residue was not removed; and (b) when the residue was swept off the top of the rows. They also reported that removal of residue did have a negative effect on subsequent plant-cane crops. Recently, Arceneaux and Selim (2012) investigated the long-term impact of post-harvest crop residue management on the yield of sugarcane grown on two different soils for three production cycles, a total of 10 crops. Retaining the residue resulted in reductions for yield, stalk population and commercially recoverable sucrose, but only reductions in cane and sugar yield were statistically significant. Burning resulted in an average sugar yield increase of 0.96 Mg ha -1 over full retention of residue and 0.64 Mg ha -1 over sweeping residue into wheel furrows. They concluded that yield reductions from the non-removal of crop residue was temporal in nature and confined to ratoon crops within a production cycle. Reductions in sugar yield when the residue was mechanically removed (sweeping) were due to the damage caused by mechanical actions of the sweeper during the process of residue removal to the ratoons. Aggressive mechanical sweepers fitted with steel serrated blades are particularly damaging to partially exposed ratoons. In other grass crops, such as perennial ryegrass and tall fescue, mechanical removal of the residue has been reported to be as effective as burning (Young et al., 1999). Therefore, reduction in sugarcane yield can be minimized if mechanical residue removal from the top of the cane rows is achieved without excessive ratoon damage. Improvement in mechanical residue removal minimizes ratoon damage as well soil losses from the top of the 2

3 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 sugarcane rows. Improved mechanical residue removal is likely the key to the adoption by sugarcane producers of sweeping as an alternative to burning. The primary purpose of this study was to evaluate the effect of post-harvest residue management on sugarcane crop yield and water quality at the field scale. Specifically, the focus was to implement residue management strategies by use of a new implement (sweeper) capable of removing sugarcane residue off the top of the rows with minimal soil surface losses and damage to cane ratoons. To achieve this goal, three management strategies were evaluated: (1) burning the mulch after harvest; (2) sweeping the mulch off the top of the row; and (3) leaving the mulch on the field. Burning is currently the recommended best management practice in Louisiana. A viable alternative to burning must result in reproducible and comparable cane yields. Thus, sugarcane plant population and cane yield parameters were measured at each site for each treatment. Field runoff volume was measured along with water quality parameters including water turbidity, total, soluble, and suspended solids, dissolved P, nitrate N, and ammonium N. EXPERIMENTAL METHODS The objective was to evaluate a mechanical residue removal implement for the purpose of minimizing loss of sugarcane yield and loss of surface soil. The implement, used in this study was manufactured by Orthman Manufacturing Co., Lexington, NE It uses 3 pair of 18-tooth, 60-cm diameter, rubber tine spider wheels (Part # ) set at 45 angles from a center mounting arm (Part # ), 3 on each side. The mounting arm assembly connects to a steel tool bar set perpendicular to the direction of travel. As tested the implement included three mounting arm assemblies, set apart by 1.83-m, to sweep three 1.83-m rows at a time, held on track by two 54-cm flat disc guide wheels (Part # and ), one extending past the outside mounting arms by 0.91 m on each side. The implement was utilized with the assumption that improvement in mechanical residue removal is a prerequisite to minimize ratoon damage and soil losses from the top of the sugarcane rows. As such it is likely the key to the adoption by sugarcane producers of sweeping as an alternative to burning. To achieve this, large field studies were carried out at four experimental sites during 2012 through 2016 (Table 1). In 2012, two experiments were established near Paincourtville, LA, one at the Dugas farm and one at the Gravois farm. At the Gravois location three plots, each > 0.4 ha, of commercial sugarcane variety HoCP (Tew et al., 2005), were delineated and the following management practices were implemented; (1) burning the mulch after harvest; (2) sweeping the mulch off the top of the row and into the wheel furrow; and (3) leaving the mulch on the soil surface as-is. In addition, to monitor water quality, an edge of field sampling was carried out for each treatment at the Gravois site. Specifically, each treatment was instrumented with ISCO water sampler, flow module, area velocity meter, rain gauges, and 45-cm H-type flume. The experiments at the Dugas farm consisted of the same three treatments and included two replications of each treatment. All plots were planted to the commercial sugarcane variety L or L (Gravois et al., 2010; Gravois et al., 2011). Each 0.10 ha plot consisted of 6 rows spaced approximately 1.83 m apart and 91.4 m in length. At both of the Gravois and Dugas sites, all treatments were applied in January of 2013 after the plant-cane crop was harvested in December of

4 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Stalk counts were collected in August The first ratoon cane was harvested in December 2013 for both sites. Ten stalk samples were collected at harvest and processed at the LSU Sugar Research Station in St. Gabriel, LA, using a Dedini shredder and Spectracane 200 near infrared (NIR) spectrometer (Lower Hutt, New Zealand). Analyses included BRIX, commercially recoverable sucrose (CRS), sugar purity, and percent sucrose. In the meantime, water quality was monitored throughout the growing season and samples collected when rainfall amounts were sufficient to initiate runoff. Collected samples of effluent solution were analyzed for sediment, ammonium N, nitrate N, and dissolved P. During 2014 the mulch treatments were implemented to the same plots in January for the Gravois farm site only. Runoff samples from edge of field were collected from each plot from March to the end of October. A stalk count was obtained in September of The second-ratoon cane was harvested on December 2, In 2015, the Duson farm site was initiated and consisted of the same three mulch treatments with two replications. The 0.08 ha plots consisted of 3 rows, 1.83 m apart, running 146 m long. Second ratoon of commercial sugarcane variety L was harvested in December of 2014 (Gravois et al., 2012). The treatments were applied in January of Stalk counts were collected in August of The 3 rd ratoon cane was harvested on October 2, The site at the LSU Sugar Research Station consisted of the same mulch treatments and four replications. The ha plots consisted of 3 rows, spaced 1.83 m apart, and 137 m long. Plant cane of variety L was harvested in December of 2014 (Bischoff et al., 2009). The treatments were applied in January of Stalk counts were collected in August of The 1 st ratoon cane was harvested on November 16, This experiment was continued in The treatments were applied in January of The 2 nd ratoon cane was harvested on November 28, Stalk counts were collected in November, The treatments were applied the final time in January of The 3 rd ratoon cane was harvested in November, Data were pooled to test the effects of mulch treatments on field-scale yields of ratoon sugarcane. Not all test years at each location included sufficient replication for statistical inferences to be made. Thus, pseudo-replications were pooled across variety to estimate mean square error needed to make inference with regards to the treatments imposed (Hurlbert, 1984). A separate ANOVA was conducted for St. Gabriel data where sufficient replications each year were available. Yield data were analyzed using the mixed procedure in SAS version 9.0 (SAS Institute, Cary, NC). Treatment and ratoon were considered fixed effects and site and replication were random effects. Means of significant effects were separated using the PDIFF option with the SAXTON macro at the P = 0.05 level (Saxton, 1998). RESULTS AND DISCUSSION Sugarcane Yield Sugarcane population, stalk weight, cane yield, commercially recoverable sucrose and sugar yield were relatively consistent across residue management practices. (Table 2). Cane yields measured for first through third ratoon were statistically similar for the burn (61.1 Mg ha -1 ), sweep (59.6 Mg ha -1 ), and mulch (62.0 Mg ha -1 ) treatments, when data were combined across year and variety (Table 3). A similar relationship was evident 4

5 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 for commercially recoverable sucrose and sugar yield, where the residue management treatments resulted in average commercially recoverable sucrose and sugar yields for burn, mulch, and sweep treatments of 129, 124, and 130 kg Mg -1, and 7307, 7294, and 7354 kg ha -1, respectively. However, a significant difference in cane yield was observed by ratoon, where 1 st ratoon cane out yielded second and third ratoon cane with 67.2, 60.5, and 54.9 Mg ha -1, respectively (Table 3). First thru third ratoon commercially recoverable sucrose and sugar yields were 111, 120, and 153 kg Mg -1, respectively, and sugar yields were 8071, 7988, and 5895 kg ha -1, respectively. In general, sugarcane ratoon was a greater factor in the cane yield parameters than was crop residue treatments. But, the ratoon effect was not consistent across yield parameters, for example, as cane yields were similar for second and third ratoon, and sugar yields were similar for first and second ratoon (Table 3). Results from the sweep, mulch, and burn indicated similar yields when compared to the conventional burn treatment. This result was consistent for the two different locations as shown. For Gravois farm, the total yield for the mulch, sweep, and burn treatments was 64.9, 78.1, and 78.8 Mg ha -1, respectively. For Dugas farm, the respective yields were 73.2, 74.8, and 75.9 Mg ha -1. These results are in contrast to earlier work reported on sugarcane since 2001 with losses of yields from 9 to 14% when sweepers were used compared to the conventional burn treatment. Residue treatment and ratoon did not statistically affect sugarcane stalk population observed over the tests (Table 2). Data were variable, however. The average stalk population was 98,000 ha -1, but ranged from 68,000 to 134,000 ha -1. Varietal means were , , , , and for HoCP , L , L , L , and L , respectively. The data can be compared to the Variety Release Program outfield tests over the period. The average stalk population for the varieties used in the present study was 73,000 ha -1, and ranged from 54,000 to 100,000 ha -1. Varietal means (ha -1 ) in the outfield tests were , , , , and for HoCP , L , L , L , and L , respectively. The dissimilarity could be the result of residue management practices, as the outfield tests were burned, and a reduction of 2000 stalks ha -1 in ratoon population resulting from residue burning during winter dormancy, when compared to sweeping of the residue, was previously reported (Viator et al., 2009). Stalk weights were not different due to residue management or ratoon (Table 2). The average weight was 0.78 kg and ranged from 0.41 to 1.25 kg. The data were comparable to the outfield test of the same varieties with an average of 0.85 kg and a range of 0.63 to 1.22 kg. Ten stalk samples of L from each treatment were collected at harvest, weighted, and milled at the Sugar Research Station in St. Gabriel (Table 3). Whole stalks of variety L are more difficult to harvest and plant mechanically because of the abundance of green and brown leaf material, as compared to other commercial varieties in Louisiana. For example, L produced significantly larger amounts of dry sugarcane leaf material, when compared to HoCP or L , on 60% of dates sampled over two years (White et al., 2018). Post-harvest residue of the preceding crop did not impact the observed cane yield, commercially recoverable sucrose, or sugar yield of the subsequent ratoon crop of L harvested at St. Gabriel. Burning, mulching, and sweeping produced similar cane yields, 59.5, 63.9, and 58.0 Mg ha -1, respectively, at St. Gabriel over the three crops of L Averaged across residue 5

6 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana treatments the first-ratoon crop out yielded the second- and third-ratoon crop at 70.1, 54.7, and 56.7 Mg ha -1, respectively. Observed commercially recoverable sucrose were higher for first and second ratoon, when compared to third ratoon, with mean values of 122, 123, and 108 kg Mg -1, respectively. Sugar yield fell each year independent of residue management with first, second, and third ratoon values of 8588, 6711, and 6056 kg ha -1, respectively. In 2014, cane yield from the Gravois site for the mulch, sweep and burn treatments was 59.5, 62.9, and 64.4 Mg ha -1, respectively; the difference for sweep and burn was less than 2.5%. Yield results based on the management strategies in 2014 of sweep and burn were very comparable; 6913 versus 6925 kg sugar ha -1, respectively. Yield from the Duson site was very low due to extreme drought conditions in the surrounding region, where less than 5 cm were received between June and October, The average cane yield for mulch, sweep, and burn treatments was 39.0, 33.9, and 33.9 Mg ha -1, respectively. Drought conditions may have perhaps led to the observation of higher yields when the mulch was not removed or burned. Nevertheless, cane yield and total sugar yield (5280 versus 5360 kg ha -1, respectively) were comparable between the sweep and burn treatments at Duson. Therefore, in spite of summer drought at Duson, the sweep treatment did not result in yield reduction when compared to the burn treatment. The St. Gabriel site did not experience droughts of the magnitude of Duson site during 2015 where considerably higher yields were realized (data not shown). In fact, average cane yields were comparable for all treatments; 71.8, 69.4, and 69.1 Mg ha -1 for mulch, sweep, and burn treatments, respectively. Cane yields from St. Gabriel and Dugas sites for 2016 also showed a similar trend between mulch, sweep, and burn treatments. For St. Gabriel, 2016 average cane yields were 53.0, 57.9, and 53.2 Mg ha -1, and at Dugas, cane yields for L (68.0, 77.0, and 80.1, respectively) and L (87.1, 87.6, and 89.4 Mg ha -1, respectively) for mulch, sweep, and burn management. Most clear is the observation that cane yields were comparable for the sweep and the burn treatments. Water Quality Effluent or runoff water samples during 2013 and 2014, for all management treatments were collected from the Gravois site. The samples were collected following each rainfall event that triggered runoff. Collected runoff samples were analyzed in the laboratory based on approved EPA protocols. This includes total and suspended solids (TS and TSS), turbidity, nitrate N, ammonium N, and dissolved P (Fig. 1 9). Because of distinct rainfall distributions, we collected 22 water quality samples during 2013 compared to only 14 samples during This is despite the fact that, during the sampling period, rainfall amounts were significantly lower in 2013 (72.9 cm) than 2014 (89.4 cm). Sampling was initiated following the final herbicide application and cultivation. In Louisiana this is referred to as a layby treatment and is commonly made in early May and prior to the closure of plant canopy. During 2013 and 2014, concentrations of the total solids in the effluent from all treatments shown in Fig. 1 and 4 indicate there was no consistent differences among the three treatments. Average sediment concentrations were 4400, 3500 and 7700 ppm for the sweep, burn and mulch treatments, respectively. Results from suspended solids shown in Fig. 2 and 5, mimic those for total solids with an obvious decrease during the growing season and prior to 6

7 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 harvest. Increased turbidity was observed during 2014 compared to 2013 which is likely due to the higher rainfall amount in Based on the above results, the use of a modified sweeper as a management strategy did not result in increased soil loss or turbidity when compared to the conventional burn treatment. Higher soil losses were observed by Selim et al. (2010) with averages between 8,000 and 10,000 ppm from the effluent in Wikoff sub-watershed over two sugarcane growing seasons ( ). In contrast, Bakr et al. (2012) reported one-order magnitude lower sediment concentrations in the effluent from bare soils that received 5 cm of compost. Concentrations of dissolved P, nitrate N, and ammonium N in the effluent from the runoff were extremely low (Fig. 7-9). Dissolved P concentrations did not exceed 1.0 ppm during the entire sampling period with a mean value of 0.4 ppm for all treatments. The results are consistent with Selim et al. (2010) reporting that effluent dissolved P concentrations that did not exceed 1.3 ppm in the effluent over two growing seasons ( ). Such values of P are consistent with that of bio-solid amended soils (Sharpley, 1995). Nitrate N losses were also extremely low and exhibited no obvious pattern over the sampling period. The only exception is that for the burn treatment where significantly high nitrate levels were observed in effluent samples collected in May-June This high concentration may be an artifact of typical spring fertilizer applications to sugarcane ratoons. Nevertheless, nitrate levels after mid-july were extremely low for all treatments (0.2 to 1.1 ppm). These results imply that the environmental impact of nutrient losses from sugarcane for all three management strategies is minimal. Specifically, the use of a sweeper as a management practice does not contribute additional nutrient losses from sugarcane fields when compared to the conventional burn treatment. Based on edge of field data, losses of sediment, and P and N, are comparable for all treatments. Based on our results we conclude that there was no significant difference observed for the total soil loss (suspended and total solids), turbidity, phosphorus or nitrogen. In fact, the influence of the sweeper on soil and nutrient losses were comparable to runoff from burn and mulch management strategies. Furthermore, sugarcane yield with the modified sweeper was not significantly different from mulch or burn treatments. These findings are based on the results from five growing seasons ( ), five farms, and three locations. LITERATURE CITED Arceneaux, A. E. and H. M. Selim Mulch management strategies and sugarcane yield. Proc. Int. Soc. Sugar Cane Technol. 32: Bakr, N., D.C. Weindorf, Y. Zhu, A. E. Arceneaux, and H.M. Selim Evaluation of compost/mulch as highway embankment erosion control in Louisiana at the plot-scale. J. of Hydrol :

8 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Bischoff, K.P., K.A. Gravois, T.E. Reagan, J.W. Hoy, C.M. Laborde, C.A. Kimbeng, G.L. Hawkins, and M.J. Pontif Registration of L sugarcane. J Plant Reg 3(3): Deliberto, Michael A., Brian M. Hilbun, and Michael E. Salassi Projected Costs and Returns Crop Enterprise Budgets for Sugarcane Production in Louisiana, Louisiana State University Agricultural Center, A.E.A. Information Series No. 316 (27 pp). Gravois, K.A., K.P. Bischoff, C.M. LaBorde, J.W. Hoy, T.E. Reagan, M.J. Pontif, C.A. Kimbeng, G.L. Hawkins, D.R. Sexton, and D.P. Fontenot Registration of L sugarcane. J Plant Regis 4(3): Gravois, K.A., K.P. Bischoff, M.J. Pontif, C.M. LaBorde, J.W. Hoy, T.E. Reagan, C.A. Kimbeng, B.L. Legendre, G.L. Hawkins, D.R. Sexton, and D.P. Fontenot Registration of L sugarcane. J Plant Reg 5(2): Gravois, K.A., K.P. Bischoff, J.W. Hoy, T.E. Reagan, M.J. Pontif, C.A. Kimbeng, G.L. Hawkins, D.P. Fontenot, D.R. Sexton, and A.J. Orgeron Registration of L sugarcane. J. Plant Reg 6 doi: /jpr crc. Hulbert, S.H Pseudoreplication and the design of ecological field experiments. Ecol. Monogr. 54(2): Richard, E. J, Jr Management of chopper harvester-generated green trash blankets: A new concept in Louisiana. Proc. Int. Soc. Sugar Cane Technol. 25: Richard, E. J, Jr, and R. M. Johnson Green trash blankets: Influence on ratoon crops in Louisiana. J. Am. Soc. Sugar Cane Technol. 23:93. Saxton, A.M A macro for converting mean separation output to letter groupings in Proc Mixed. In Proc. 23rd SAS users group international, March 1999, Nashville, Cary: SAS Institute. Selim, H. M, L. Zhou and H. Zhu Herbicide retention in soil as affected by sugarcane mulch residue. J Environ Qual Selim, H. M., C-Y Jeong, A. Arceneaux and R. L.Bangtson Wikoff sub-watershed of Bayou Plaquemine Brule watershed report. Unpublished report to Nonpoint source Pollution Program, Louisiana Department of Environmental Quality. (105 pp). 8

9 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Sharply, A. N Dependence of runoff phosphorus on extractable soil phosphorus. J. Environ Qual. 23: 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(2): Viator, H.P., and J. J. Wang Effects of residue management on yield after three production cycles of a long-term sugarcane field trial in Louisiana. J. Am. Soc. Sugar Cane Technol. 31: Viator, R. P., R. M. Johnson, D. L. Boykin, and E. P. Richard Sugarcane postharvest management in a temperate climate. Crop Sci. 49: White, Jr., P.M, R.P. Viator, C.L. Webber, III, and G. Eggleston Potential losses of soil nutrients and energy content on the complete removal of sugarcane leaf material as a biomass feedstock. Sugar Tech. 20 (1): Young, W.C., III, M.E. Mellbye, and T.B. Silberstein Residue management of perennial ryegrass and tall fescue seed crops. Agron. J. 91:

10 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Table 1. Summary of field experiments conducted to test residue management treatment effects on sugarcane ratoon yields and water quality in Louisiana. Location Farm Variety Treatments Replication Paincourtville, LA Gravois HoCP Burn, Mulch, Sweep Plot size (m 2 ) Ratoon Harvest Year First Second Third None Paincourtville, LA Dugas L Duson, LA Duson L Burn, Mulch, Sweep Burn, Mulch, Sweep St. Gabriel, LA Sugar Station L Burn, Mulch, Sweep Paincourtville, LA Dugas L Paincourtville, LA Dugas L Burn, Mulch, Sweep Burn, Mulch, Sweep None None

11 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Table 2. ANOVA results for sugarcane yield parameters as affected by residue management and crop ratoon across five Louisiana farms from Population Stalk Weight Cane Yield CRS Sugar Yield F-ratio P-value F-ratio P-value F-ratio P-value F-ratio P-value F-ratio P-value Treatment (T) Crop Ratoon (C) < T x C

12 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Table 3. Burning, mulching, and sweeping affected cane yield, commercially-recoverable sucrose (CRS), and sugar yield from ratoon crops of five Louisiana sugarcane farms sampled from Treatment Cane Yield (Mg ha -1 ) CRS (kg Mg -1 ) Sugar Yield (kg ha -1 ) 1 st 2 nd 3 rd Mean 1 st 2 nd 3 rd Mean 1 st 2 nd 3 rd Mean Burn a* a a Mulch a a a Sweep a a a Mean 67.2 A 60.5 B 54.9 B 111 B 120 A 153 AB 8071 A 7988 A 5895 B *Means followed by the same lower case letter in a column, or upper case letter by yield parameter, are not different at the P<0.05 level. 12

13 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Table 4. The effects of burning, mulching, and sweeping of sugarcane crop residue on ratoon cane yield, commercially recoverable sucrose (CRS), and sugar yield for L , a high-residue variety, at the LSU Sugar Research Station in St. Gabriel, LA, in Treatment Cane Yield (Mg ha -1 ) CRS (kg Mg -1 ) Sugar Yield (kg ha -1 ) 1 st 2 nd 3 rd Mean 1 st 2 nd 3 rd Mean 1 st 2 nd 3 rd Mean Burn a* a a Mulch a a a Sweep a a a Mean 70.1 A 54.7 B 56.7 B 122 A 123 A 108 B 8588 A 6711 B 6056 B *Means followed by the same lower case letter in a column, or upper case letter by yield parameter, are not different at the P<0.05 level. 13

14 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana ` Figure 1. Concentration of total solids of runoff water collected during 2013 from edge of fields at the Gravois site for sweep, burn and mulch treatments. 14

15 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Figure 2. Concentration of suspended solids of runoff water collected during 2013 from edge of fields at the Gravois site for sweep, burn and mulch treatments. 15

16 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Figure 3. Turbidity of runoff water collected during 2013 from edge of fields at the Gravois site for sweep, burn and mulch treatments. 16

17 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Figure 4. Concentration of total solids of runoff water collected during 2014 from edge of fields at the Gravois site for sweep, burn and mulch treatments. 17

18 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Figure 5. Concentration of suspended solids of runoff water collected during 2014 from edge of fields at the Gravois site for sweep, burn and mulch treatments. 18

19 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Figure 6. Turbidity of runoff water collected during 2014 from edge of fields at the Gravois site for sweep, burn and mulch treatments. 19

20 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana Figure 7. Concentration of dissolved phosphorus of runoff water collected during 2013 from edge of fields at Gravois site for sweep, burn and mulch treatments. 20

21 Journal American Society of Sugar Cane Technologists, Vol. 38, 2018 Figure 8. Concentration of nitrate of runoff water collected during 2013 from edge of fields form Gravois site for sweep, burn and mulch treatments. 21

22 Selim et al.: Yield and Water Quality for Different Residue Managements of Sugarcane in Louisiana 0.25 Sugarcane 2013 SWEEP BURN MULCH 0.2 Ammonia (ppm) Figure 9. Concentration of ammonium of runoff water collected during 2013 from edge of fields form Gravois site for sweep, burn and mulch treatments. Date 22