IMPROVING CANE PRODUCTIVITY WITH DUAL ROW PLANTING IN MAURITIUS By F.M. ISMAEL, S. SEERUTTUN, C. BARBE and A. GAUNGOO

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1 IMPROVING CANE PRODUCTIVITY WITH DUAL ROW PLANTING IN MAURITIUS By F.M. ISMAEL, S. SEERUTTUN, C. BARBE and A. GAUNGOO Mauritius Sugar Industry Research Institute, Réduit, Mauritius KEYWORDS: Sugarcane, Row Spacings, Dual Rows, Cane and Sugar Yield. Abstract DUAL row planting, consisting of pairs of cane rows 0.5 m apart with 1.8 m between their centres, was studied in twelve field trials between 1999 and Dual rows were compared to the standard row spacing of 1.6 m. Two N fertiliser rates (normal and + 25%) and two cane sett densities (normal and a reduced amount) were included as treatments in the early trials whereas the response of sugarcane varieties to the new spacing was evaluated later. Increases in cane yields with dual row planting varied between 3% and 28% depending on cane varieties; M 1400/86 and R 579 were the most responsive with a mean increase varying between 8% and 16%. Yields of plant and ratoon cane showed that dual rows can be planted with an equivalent amount of cane setts and using the same rate of fertiliser as for the conventional spacing. No difference in sucrose content has been observed between the two spacings. Weed management improved with dual rows; and critical periods of weed competition were shortened by at least four weeks. Mechanised harvest of dual rows at some of the sites showed that the pairs of rows can be cut simultaneously without any difficulty; the efficiency of the machines also improved with less driving distance per hectare, less turning time and a higher pour rate. Dual row planting is being increasingly adopted as initial results from commercially planted fields are confirming the gain in productivity. Introduction Sugarcane yield is a function of the number and the weight of individual millable stalks. These yield components may be modified by changing the row spacing. The optimum row spacing not only depends on agro-climatic conditions, cane variety and economic considerations in terms of inputs, but also on the need to accommodate mechanised field operations. In Mauritius, sugarcane inter-row spacings have not changed significantly for more than a century. At the start of the 20 th century, cane setts were planted in holes with row spacing varying between 1.20 m and 1.50 m (De Sornay, 1936). These row spacings were maintained when cane was subsequently planted in continuous furrows. Previous studies on the optimum row spacing with respect to agro-climatic conditions and cane varieties showed no significant difference in cane and sugar yield with row spacings of 1.0 m, 1.30 m, and 1.60 m but inter-row spacing of 1.95 m caused a reduction in yield (Rouillard, 1970). In the late 1970s, an alternate spacing of 2.25 m and 0.95 m that did not change the planting density was tested in order to intensify food crop production in the wider inter-row. Cane yield was equally good with that spacing, but the system was not generally adopted because of lack of interest among planters for food crop production in ratoon cane. Today sugarcane row spacing varies between 1.20 m and 1.62 m; the most common spacings used are 1.45 m and 1.62 m. In recent decades, the wider spacings have been increasingly adopted because inter-rows of more than 1.50 m facilitate movement of standard tractors and loading equipment. 220

2 The need to improve cane productivity has rendered a review of the cropping system necessary, in particular cane planting density and row spacing. The planting of sugarcane at higher densities has been studied in a number of countries, including India, USA, South Africa and Australia, with varying degrees of success depending upon the row spacings used, the prevailing environmental conditions, the level of mechanisation and the duration of the crop growth period (Bull and Bull, 2000a). In Australia, one of the techniques of High Density Planting, dual rows, has been extensively tested. Dual rows consist of pairs of rows 0.5 m apart with 1.8 m between their centres. The average increase in yield of 20% to 25% has been reported with dual rows (Bull and Bull, 2000a; BSES, 1997). These results were confirmed by simulation modelling of crop growth that showed significant increases in light interception by the dual row crop prior to canopy closure (Bull and Bull, 2000b). The adoption of dual row planting by Australian producers has, however, been very slow as it requires some modifications to planting and harvesting machines (Norris et al., 2000). The promising results obtained with dual rows in Australia motivated the Mauritian sugar industry to evaluate the technique under local conditions. The specific objectives of the trials were to assess both the yield responses of local cane varieties to dual rows and the inputs, such as amount of planting material and fertiliser, required. Materials and methods Dual row planting was evaluated in twelve trials established in different agro-climatic regions and soil groups (Table 1). Dual rows were compared to the standard row spacing in three trials at Chebel, Constance and Astroea in Four other trials were planted in 2000 at Union, Bon Espoir, Olivia, and Savannah. In 2002, another three trials were laid down at Alma, Terracine and Bonne Veine. The last two trials were located at Bonne Veine and Union Park in 2003 and 2004, respectively. The influence of dual row planting on canopy development was assessed by measurements of photosynthetic active radiation (PAR) transmitted at two weeks interval using a ceptometer. The effect of sett density, the application of additional nitrogen, and the response of cane varieties were also investigated (Table 2). Table 1 Characteristics of trial sites. Site Soil type* Elevation (m) Rainfall, mm Irrigation Date planted (mean of 30 yrs) Chebel L Yes Constance L Nil Astroea F Nil Union L Nil Bon Espoir P Nil Olivia L Nil Savannah L Yes Alma B Nil Terracine L Nil Bonne Veine B Nil Bonne Veine H Nil Union Park F Nil * Parish and Feillafé (1965) Planting sugarcane in dual rows represents about 70% increase in row length per hectare compared to the standard spacing, which would result in the use of more planting materials and consequently an increase in cost. For this reason the effect of reducing the amount of cane setts was tested at Chebel, Astroea and Union. The setts were placed in a single row along the furrow instead of double rows so that the total amount used was equivalent to that of the standard practice. Table 2 Treatments and experimental details. 221

3 Site Variety Main plot (spacing) Subplot Sub-subplot Chebel R 575 DR Vs 1.62 m Sett density Fertiliser Constance R 575 DR Vs 1.62 m Fertiliser Astroea R 570 DR Vs 1.62 m Sett density Fertiliser Union M 695/69 DR Vs 1.62 m Sett density Fertiliser Bon Espoir R 570 DR Vs 1.62 m Fertiliser Olivia M 1551/80 and M 1658/78 DR Vs 1.62 m Variety Fertiliser Savannah M 96/82 and M 695/69 DR Vs 1.5 m Variety Fertiliser Alma M 52/78, M 1400/86, M 2024/88 and R 579 DR Vs 1.62 m Variety Terracine M 1400/86, R 570, R 573 and R 579 DR Vs 1.62 m Variety Bonne Veine M 1400/86 and R 579 DR Vs 1.62 m Variety Bonne Veine M 703/89 DR Vs 1.62 m Union Park M 1394/86 DR Vs 1.5 m DR : Dual row planting Fertilisation of sugarcane is based on the expected yield. The recommended rate of nitrogen applied for standard row spacing varies from 1.2 to 1.4 kg per tonne of millable stalks depending on soil type (STASM, 2002). Hence, an expected increase in yield with dual rows would normally need an additional amount of N. In the early trials conducted in Australia, the amount of N was increased by 20% to 25% (BSES, 1997). The trials at Chebel, Constance, Astroea, Union, Bon Espoir, Olivia and Savannah included two rates of N, namely the recommended rate and recommended rate + 25%. In Australia, differential responses were observed between cane varieties under dual row planting (Bull and Bull, 2000a). In five trials, the responses of two or four cane varieties with differing characteristics were evaluated. At all sites, cane was planted manually in plots that varied in size between 200 m 2 and 500 m 2. A split-split-plot design was used with spacing as the main-plot treatment at all sites and the sub-plot and sub-sub-plot treatments consisted of either sett density or fertiliser rate or variety. Each treatment was replicated at least four times. Data recorded included the amount of planting material used, cane growth (tillering and number of millable stalks), cane and sugar yields at harvest for the plant and ratoon cane. Results and discussion Tillering and millable stalks Dual row planting resulted in an increase in the number of tillers per m 2, and the maximum increase over conventional practice coincided with the peak in tillering (Figure 1). Fig. 1 Effect of dual row planting on tillering and number of millable stalks. The difference observed in favour of the new spacing was reduced at harvest; an average 222

4 increase of 11.0% in number of millable stalks was obtained with dual row planting (Table 3). Table 3 Effect of dual row planting on the number of millable stalks. No. of Millable stalks /ha Site Crop cycle Conventional Dual rows Chebel Constance PC+ 5R Astroea PC+ 5R Union Bon Espoir Olivia Savannah Alma PC+ 3R Terracine PC+ 3R Bonne Veine PC+ 2R Bonne Veine PC+ 1R Union Park PC+ 1R Mean of plant cane (PC) and ratoons (R) Cane yield The yield response to dual row planting varied across sites and years. The mean yield of plant cane and ratoon crops showed that dual rows were significantly higher at Chebel, Bonne Veine, Union Park, Terracine and Alma (Table 4). Table 4 Effect of dual row planting on cane yield. Yield (t/ha) + Site Crop cycle Conventional Dual rows Chebel ** Constance PC+ 5R Astroea PC+ 5R Union Bon Espoir Olivia Savannah Alma 2 PC+ 3R ** Terracine 2 PC+ 3R * Bonne Veine 1 PC+ 2R * Bonne Veine PC+ 1R Union Park PC+ 1R Two varieties, 2 Four varieties *, ** significantly different at 5% and 1% respectively Cane yield is a function of number and weight of millable stalks, with weight in turn being dependent on stalk height and diameter. The higher number of millable stalks with dual row planting should have resulted in a more pronounced difference in cane yield. However, at some sites, a slight decrease in stalk diameter was recorded with dual rows. Stalk height was not affected by planting method. Variety response The response of cane varieties to dual row planting was observed in trials established in 2002 at Alma, Terracine, Bonne Veine and Union Park. At Alma, dual row planting increased cane yields on average by 19%, 15.6% and 13.3% for varieties M 52/78, M 1400/86 and R 579, respectively (Table 5). M 2024/88 did not respond favourably because of lodging. The good response of R 579 was similar at both Terracine and Bonne Veine with 8.2% and 28.4% increases respectively. M 1400/86 was less responsive at Terracine but yielded 8% more with dual rows at 223

5 Bonne Veine. R 570 and R 573 performed equally well in dual rows at Terracine with yield increases of 5%. Table 5 Response of cane varieties to dual row planting. Yield (t/ha) + Stalk diameter (cm) Stalk height (m) Site Conventional Dual rows Conventional Dual rows Conventional Dual rows Alma M 52/ ** M 1400/ ** M 2024/ ** R ** Terracine M 1400/ R R R Bonne Veine M 1400/ * R * + Mean of PC + 3R at Alma and Terracine PC + 2R at Bonne Veine *, **, significantly different at 5% and 1% respectively The positive response of some varieties may be associated with their morphological characteristics. It seems that the leaf canopy architecture is an important factor when planting density is increased; cane varieties with erect stalk and leaf may have been more efficient in intercepting radiation. Varieties with recumbent leaves or those having a tendency to lodge were less responsive to dual row planting, e.g. M 2024/88 lodged heavily, leading to a yield reduction with dual row planting. Effect of dual row planting on sucrose content At all sites, irrespective of the cane variety, row spacings had no significant effect on sucrose content (IRSC). This confirms results obtained in previous spacing trials carried out locally (Rouillard, 1970) and those obtained in High Density Planting trials in Australia (Bull and Bull, 2000a). Fertilisation and dual row planting The additional 25% N, to compensate for the extra biomass produced by dual row planting, had no effect on cane yields (Table 6). It seems that the amount recommended for conventional planting is more than required, as N use efficiency by sugarcane in Mauritius is generally low and rarely exceeds 40% (Ng Kee Kwong and Deville, 1987). Trials carried out by BSES (Bureau of Sugar Experiment Stations, Australia) also showed no yield response to additional N when rates above 120 kg/ha were used for high density planting (Bull and Bull, 2000b). Amount of planting material Placing cane setts in single rows (with a slight overlapping at ends) along the furrows of the dual rows resulted in a total amount of planting material similar to that used conventionally. Results recorded at Chebel, Astroea and Union showed that the reduced amount of cane setts per row length had no adverse effect on cane yield (Table 7). All trials established later on were planted with this reduced sett density; the cane yields obtained with the new spacing do not indicate any necessity to use more planting material. Table 6 Effect of additional nitrogen on the yield of cane planted in dual rows. 224

6 Yield (t/ha) + Site Crop cycle Spacing NF F+ Chebel Conventional Dual rows Constance PC+ 5R Conventional Dual rows Astroea PC+ 5R Conventional Dual rows Union Conventional Dual rows Bon Espoir Conventional Dual rows Olivia Conventional Dual rows Savannah Conventional Dual rows Union Park PC+ 3R Conventional Dual rows Mean of plant cane (PC) and ratoons (R) NF Normal fertiliser rate F+ Additional 25% N Table 7 Effect of sett density on the yield of cane planted in dual rows. Planting material (t/ha) Yield (t/ha) + Site Spacing Standard Reduce Standard Reduce Chebel Conventional Dual rows Astroea Conventional Dual rows Union Conventional Dual rows Mean of PC + 4R at Chebel and Union, PC + 5R at Astroea Dual row planting and weed management It was observed that fewer weeds were present in the plots planted in dual rows; light measurements (PAR) within the cane rows and inter-rows showed that more light was intercepted by the cane canopy with the higher plant density. Canopy closure was achieved at least four weeks earlier when cane was planted in dual rows (Figure 2). This advantage may result in savings with regard to the cost of weed management; one week of chemical weed control varies between 3 and 5 dollars (US) per hectare. Mechanical harvest of dual rows Mechanised harvest of non-experimental plots planted in dual rows at some of the sites showed that the pairs of rows can be harvested simultaneously without problem, even in older ratoons. In fact, the efficiency of the machines was improved considerably with less driving distance per hectare, less turning time and an increased pour rate. 225

7 PAR intercepted (%) DR 1.62 m weeks Weeks after harvest Fig. 2 Light interception by sugar cane canopy. Conclusions After six years of evaluation, the potential of dual row planting as a means to increase sugarcane productivity has been demonstrated. An increase in cane yield between 8 and 12% depending on the cane variety may be obtained. Dual row planting enables significant savings on weed management, and improves efficiency of chopper-harvesters. It does so without increasing inputs (planting material and fertiliser). Although this new spacing has only been recommended since early 2006, many Mauritian growers had already adopted dual row planting. Some 1000 ha commercially planted during the last three years with such spacing are confirming the gain in productivity. REFERENCES BSES (1997). High Density Planting. Fact sheet (FS1197) published by Bureau of Sugar Experiment Stations (BSES), Bundaberg, Australia. Bull, T.A. and Bull, J.K. (2000a). High density planting as an economic production strategy: (a) Overview and potential benefits. Proc. Aust. Soc. Sugar Cane Technol., 22: Bull, T.A. and Bull, J.K. (2000b). High density planting as an economic production strategy: (b) Theory and trial results. Proc. Aust. Soc. Sugar Cane Technol., 22: De Sornay, P. (1936). Manuel de la canne à sucre à l usage des chargés des cours et des élèves des grandes écoles coloniales. Port Louis: General Printing & Stationery Cy Ltd. Ng Kee Kwong, K.F. and Deville, J. (1987). Residual fertiliser nitrogen as influenced by timing and nitrogen forms in a silty clay soil under sugar cane in Mauritius. Fert. Res. 14: Norris, C.P., Robotham, B.G. and Bull, T.A. (2000). High Density Planting as an economic production strategy: (c) A farming system and equipment requirements. Proc. Aust. Soc. Sugar Cane Technol., 22: Parish, D.H. and Feillafe, S.M. (1965). Notes on the 1: soil map of Mauritius. Mauritius Sugar Industry Research Institute, Réduit. Occasional Paper 22. Rouillard, G. (1970). Results on spacing experiments. Rep. Maurit. Sug. Ind. Res. Inst. 1969: STASM (2002). Manual of Sugar Cane Agronomy. Published by Société Technologie Agricole et Sucrière de Maurice. 110 p. 226

8 AMELIORATION DE LA PRODUCTIVITE DE LA CANNE AVEC LA PLANTATION DE RANGS JUMELES A L ILE MAURICE Par F.M. ISMAEL, S. SEERUTTUN, C. BARBE et A. GAUNGOO Mauritius Sugar Industry Research Institute, Réduit, Mauritius fismael@msiri.intnet.mu MOTS-CLÉS: Canne à Sucre, Ecartement entre Rangs, Rangs Jumelés, Rendement Canne, Rendement Sucre. Abstract LA PLANTATION de rangs jumelés, constitués de paires de lignes de canne ayant un écartement de 0.5m et dont les centres des paires sont séparés de 1.8 m, a été étudiée dans douze essais au champ entre 1999 et Les rangs jumelés ont été comparés à l'écartement standard de 1.6 m. Deux doses d'engrais azoté (normale et + 25%) et deux densités de boutures de canne (une normale et une réduite) ont été inclues comme traitements dans les premiers essais tandis que la réponse des variétés de canne à sucre au nouvel espacement a été évaluée plus tard. Les augmentations de rendements avec plantation en rangs jumelés ont varié de 3 à 28% selon les variétés de canne ; M 1400/86 et R 579 furent les plus sensibles avec une augmentation moyenne variant entre 8% et 16%. Les rendements en vierge et en repousses ont montré que des rangs jumelés peuvent être plantés avec les mêmes quantités de boutures de canne et d'engrais que celles utilisées avec l'écartement standard. On n a observé aucune différence dans le taux de saccharose entre les deux espacements. La gestion des mauvaises herbes fut améliorée avec les rangs jumelés; et les périodes critiques de concurrence des mauvaises herbes ont été raccourcies d au moins quatre semaines. La récolte mécanique des rangs jumelés sur certains sites a montré que les paires de rangées peuvent être coupées simultanément sans aucune difficulté ; l'efficacité des machines a également été améliorée avec moins de distance roulement par hectare, moins de temps de manoeuvre et un taux de déchargement plus élevé. La plantation en rangs jumelés est de plus en plus en plus adoptée au vu des résultats initiaux de parcelles commerciales confirmant le gain de productivité. MEJORANDO LA PRODUCTIVIDAD DE CAÑA CON SIEMBRAS DE SURCO DOBLE EN MAURICIO Por F. M. ISMAEL, S. SEERUTTUN, C. BARBE y A. GAUNGOO Mauritius Sugar Industry Research Institute, Réduit, Mauritius fismael@msiri.intnet.mu PALABRAS CLAVE: Caña de Azúcar, Espacios entre Surco, Surcos Dobles, Rendimiento de Caña y Azúcar. Resumen LA SIEMBRA de surcos dobles, consistente en parejas de surcos de caña, separados 0.5 m con 1.8 m entre sus centros, fue estudiada en doce ensayos de campo entre 1999 y Los surcos dobles fueron comparados con el espaciamiento estándar de 1.6 m. Dos dosis de fertilizante N (normal y + 25%) y dos densidades de esquejes de caña (normal y con tasa reducida) fueron incluidas como tratamientos en los ensayos iniciales, mientras que la respuesta de las variedades de caña de azúcar fueron evaluadas más adelante. Aumentos en el rendimiento de la caña de azúcar con siembras de surco doble variaron entre un 3% y 28% dependiendo de las variedades de caña; M 1400/86 y R 579 fueron las que más respondieron con un aumento promedio variando entre 8% y 16%. Los rendimientos de plantía y soca mostraron que los surcos dobles pueden ser sembrados con una cantidad equivalente de esquejes de caña y usando la misma dosis de fertilizante como en el espaciamiento convencional. No se encontró diferencias en el contenido de sacarosa entre los dos espaciamientos. El manejo de malezas mejoró con el surco doble; y los períodos críticos de competencia de malezas se redujeron en al menos cuatro semanas. La cosecha mecanizada en surcos dobles en algunas de las localidades mostró que las parejas de surcos pueden ser cortados simultáneamente sin ninguna dificultad; la eficiencia de las máquinas también mejoró al reducir la distancia de manejo por hectárea, menores tiempos de viraje y una mayor tasa de vertido. Las siembras en surco doble están siendo adoptadas cada vez más luego que los resultados iniciales de 227

9 campos comerciales confirman los aumentos en productividad. 228