improvement of sugarcane yield through increasing

XX Congresso Brasileiro de Agrometeorologia V Simpósio de Mudanças Climáticas e Desertificação do Semiárido Brasileiro Juazeiro-BA/Petrolina-PE, Brasil. 14 a 18 de agosto de 2017

“A Agrometeorologia na Solução de Problemas Multiescala”

IMPROVEMENT OF SUGARCANE YIELD THROUGH INCREASING ROOTING DEPTH AND VIGOR Henrique Boriolo Dias 1, Paulo Cesar Sentelhas 2 1

Eng. Agrônomo, Doutorando do PPG-ESA, ESALQ/USP, Piracicaba, SP, [email protected]; 2 Engenheiro Agrônomo, Prof. Associado 3, Departamento de Engenharia de Biossistemas, ESALQ/USP, Piracicaba, SP, [email protected]

ABSTRACT: Long-term simulations with APSIM-Sugarcane model for four traditional sugarcane-growing regions in Brazil were carried out to evaluate yield under different rooting depths and vigor for two contrasting soils in terms of water availability (Entisol and Oxisol). The results showed that sugarcane yield could be increased, on average, from 21.7 to 47.6 t ha-1 depending on the soil type and region. However, chemical and physical soil properties need to be managed in order to achieve this potential gain. KEY-WORDS: Saccharum spp.; APSIM-Sugarcane; Resilient agriculture. AUMENTO DA PRODUTIVIDADE DA CANA-DE-AÇÚCAR POR MEIO DE APROFUNDAMENTO DO SISTEMA RADICULAR RESUMO: Simulações para longas séries históricas com o modelo APSIM-Sugarcane para quatro regiões produtoras tradicionais de cana-de-açúcar no Brasil foram realizadas para avaliar a produtividade sob diferentes profundidades e vigor do sistema radicular em dois solos hidricamente contrastantes (Neossolo Quartzarênico e Latossolo Vermelho Amarelo). Os resultados mostraram que a produtividade da cana-de-açúcar poderia ser incrementada, na média, de 21,7 a 47,6 t ha-1 dependendo do tipo de solo e da região. Todavia, aspectos químicos e físicos de solos necessitam ser manejados para que esse ganho potencial possa ser atingido. PALAVRAS-CHAVE: Saccharum spp.; APSIM-Sugarcane; Agricultura resiliente. INTRODUCTION In Brazil, water deficit is the main cause of sugarcane yield gap (DIAS, 2016; MONTEIRO; SENTELHAS, 2017). Strategies to mitigate the sugarcane yield gap by water deficit are important to ensure present and future sugar and bioenergy requirements. Drought tolerant cultivars can minimize sugarcane yield losses under rainfed conditions (INMAN-BAMBER; SMITH, 2005). In this context, process-based models can support crop-breeding programs to understand genotype-environment interactions in water-limited environments (CHAPMAN et al., 2002). For sugarcane, Inman-Bamber et al. (2012) and Singels et al. (2016) used APSIM-Sugarcane and DSSAT/CANEGRO models to assess some traits that could be improved in the sugarcane ideotypes for water-limited environments or periods during growing season, in Australia and South Africa, respectively. Among the traits evaluated, deeper and denser roots are the most promising ones for sugarcane.



Considering the importance of water deficit in sugarcane yield gap in Brazil and the high climate variability present in the main sugarcane producing regions, the aim of this study was to evaluate sugarcane yield under different root depths and vigor in four traditional sugarcane-growing regions in Brazil, by simulations of APSIM-Sugarcane model for a long-term period. MATERIAL AND METHODS This study was developed for four traditional sugarcane-producing regions in Brazil, named Piracicaba, Ribeirão Preto and Catanduva, in the state of São Paulo, and Uberaba, in Minas Gerais. Although these locations have similar rainfall distribution patterns, they differs, at least to some extent, in terms of intensity of water stress. Weather data from 1917 to 2016 was used for Piracicaba (obtained from ESALQ/USP) and from 1980 to 2013 for other locations (obtained from INMET and CIIAGRO). Weather data when missing was filled with Brazilian Water Agency data, for rainfall, and with gridded data provided by Xavier et al. (2015), for the other variables. Sugarcane yield simulations were carried out with APSIM-Sugarcane, properly calibrated and validated by Dias (2016) for several Brazilian conditions and cultivars. The planting was simulated in April and harvested in July, followed by four 13-monthold ratoons. The final stalk population was set as 11, 10, 9, 8 and 7 stalks m−2 for each successive crop in order to represent, in a simplified way, the loss of vigor in later ratoons, which can result in yield decline. From the last harvesting in November to next planting in April, the crop was followed and straw was left on the soil surface to simulate a green cane trash blanket, a common management in the assessed locations. Nitrogen was applied for obtaining maximum yield. During the entire simulation the residue, water balance and nitrogen balances were not reset. Sugarcane yield (stalks in fresh basis) for the plant cane and four ratoons together was used for comparisons. The simulations also considered two contrasting soils in terms of water availability: an Entisol (Neossolo Quartzarênico) and an Oxisol (Latossolo Vermelho Amarelo). The soil profile data for the Entisol was obtained from RadamBrasil Project and for the Oxisol from Laclau and Laclau (2009) (Table 1). For Oxisol, the water limits was estimated through a specific pedotransfer function developed by Barros (2010). The values for root water extraction coefficient (KL) for these two soils were generated by exponential functions of Singh et al. (2014), where the first 20 cm was considered as 0.10. The values are similar to those presented by Inman-Bamber et al. (2000). For a usual soil exploration by sugarcane roots, maximum roots depth was 75 and 60 cm for Entisol and Oxisol, respectively (called “Regular” root system) (Table 1). Sugarcane root system is concentrated in the first 60-80 cm (LACLAU; LACLAU, 2009; SMITH et al., 2005), nevertheless, it can extract water up to 3 m or more (SMITH et al., 2005). In the study of Laclau and Laclau (2009) in Piracicaba, SP, maximum roots depth was 4.70 m and 4.25 m in the rainfed and the irrigated area, respectively. Trying to represent deeper roots, an increment in the root system exploration, the maximum depth was set as 175 cm and 150 cm for Entisol and Oxisol, respectively (Table 1). In addition, to increase depth, roots were also considered more efficient to extract water by increasing the lower limit (LL) to 10% and 5% for Entisol and Oxisol, respectively, similar to Inman-Bamber et al. (2012) (Table 1). The LL for the first 20



cm was not changed to avoid confounding the root depth and vigor traits with emergence rate (INMAN-BAMBER et al., 2012) (called “Deep and vigorous” root system). The hypothetical more vigorous and deeper roots for Entisol and Oxisol could extract 0.085 mm cm-1 and 2.641 mm cm-1 of water, respectively. Table 1. Root water extraction coefficients, soil bulk densities, saturated water contents, drained upper limits for two soils (Entisol and Oxisol) and lower limits and soil water holding capacities for the two root systems considered. Regular Deep and vigorous Depth KLa BDb SATc DULd e f LL SWHC LL SWHC -1 -3 -1 3 -3 3 -3 (cm) d (g cm ) (cm h ) (cm cm ) (mm) (cm cm ) (mm) Entisol 0-6 0.100 1.40 0.430 0.111 0.028 7.0 0.028 7.0 6-19 0.100 1.48 0.408 0.093 0.025 13.1 0.025 13.1 19-50 0.077 1.46 0.410 0.070 0.020 22.6 0.018 23.5 50-75 0.060 1.53 0.394 0.090 0.021 26.4 0.019 27.2 75-175 0.032 1.57 0.360 0.080 0.027 83.2 Oxisol 0-20 0.100 1.370 0.493 0.478 0.382 26.3 0.382 26.3 20-40 0.079 1.350 0.500 0.489 0.401 23.8 0.381 29.2 40-60 0.067 1.150 0.574 0.520 0.337 42.1 0.320 46.0 60-100 0.051 1.130 0.581 0.549 0.387 73.4 100-150 0.032 1.120 0.585 0.500 0.223 155.0 a e

Root extraction constant; bSoil bulk density; cSaturated water content; dDrained upper limit (-10 kPa); Lower limit (-1500 kPa); fSoil water holding capacity

RESULTS AND DISCUSSION The variability of sugarcane yield for all studied locations, simulated for two soils and two root systems, is presented in Figure 1. The variability is similar for all locations, despite their differences in yield levels. The sugarcane yield in Uberaba is, comparatively, slightly higher than other locations, which have similar levels. The yield increment for the Entisol was, on average, 23.5, 21.7, 25.2 and 27.7 t ha-1 respectively for Catanduva, Piracicaba, Ribeirão Preto and Uberaba. For Oxisol, the increment was, on average, 38.6, 30.7, 44.4 and 47.6 t ha-1 for the same sequence of locations. The relative yield gain was higher in the Oxisol because the simulations for deep and vigorous roots provided more available water than the Entisol. Comparatively, the relative yield gain for Entisol was higher in Ribeirão Preto and Uberaba than in Piracicaba and Catanduva. In the case of Oxisol, the relative yield gain for Piracicaba was slightly lower compared to other locations, which had similar relative yield gain. The increase of roots depth also provided yield increments in the simulations carried out in Australia with APSIM-Sugarcane by Inman-Bamber (2012). Nevertheless, Singels et al. (2016) in simulations with DSSAT/CANEGRO indicated



that increasing root growth rate does not necessarily leads to sucrose yield increment in South Africa conditions. According to these authors, the sink of carbon for root growth competes with stalk growth, which can reduce sucrose yield. It is important emphasize that the simulations were conducted without pest, weed, diseases and nutritional restrictions, which can also reduce sugarcane yields. Considering the nutritional aspects, both soils can limit the roots depth and exploration. It is recognize that Entisol is poor in terms of nutrients and Oxisols, in general, present limitations related to acidity in soil subsurface. These two aspects need to be addressed to explore effectively the sugarcane roots growth potential. Another aspect that needs attention is the soil compaction recently observed in several sugarcane regions caused by intense mechanization. Under such condition, sugarcane yield increments of the same magnitude found in this study could be achieve in the Brazilian fields.

Figure 1. Sugarcane yield (t ha-1) for traditional growing regions in Brazil (Catanduva, Piracicaba, Ribeirão Preto e Uberaba) for two soils with different water availability (Entisol and Oxisol) and two root systems (Regular, and Deep and vigorous) simulated by APSIM-Sugarcane model. The red squares represents the mean in the boxplot. CONCLUSIONS Increasing in the roots depth and vigor have a great potential to increment sugarcane yield in traditional Brazilian growing regions.



ACKNOWLEDGEMENTS We are thankful to the São Paulo Research Foundation (FAPESP) for the PhD. scholarship (grant number 2016/11170-2). REFERENCES BARROS, A.H.C. Desenvolvimento de funções de pedotransferência e sua utilização em modelo agro-hidrológico. 2010. 149p. Tese (Doutorado em Física do Ambiente Agrícola) – Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo, Piracicaba, 2010. CHAPMAN, S.C.; COOPER, M.; HAMMER, G.L. Using crop simulation to generate genotype by environment interaction effects for sorghum in water-limited environments. Australian Journal of Agricultural Research, v. 53, p. 379–389, 2012. DIAS, H.B. Intercomparação de modelos de simulação da cana-de-açúcar e seu uso na avaliação da quebra de produtividade e dos impactos da irrigação em diferentes regiões do Brasil. 2016. 162p. Dissertação (Mestrado em Engenharia de Sistemas Agrícolas) – Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo, Piracicaba, 2016. INMAN-BAMBER N.G., LAKSHMANAN P., PARK S. Sugarcane for water-limited environments: theoretical assessment of suitable traits. Field Crops Research, v. 134, p. 95104, 2012. INMAN-BAMBER, N.G.; SMITH, D.M. Water relations in sugarcane and response to water deficits. Field Crops Research, v. 92, p. 185–202, 2005. INMAN-BAMBER, N.G.; ZUND, P.R.; MUCHOW, R.C. Water use efficiency and soil water availability for sugarcane. Proceedings of the South African Sugar Technologists Association, Mount Edgecombe, v. 22, p. 264-269, 2000. LACLAU, P.B.; LACLAU, J.P. Growth of the whole root system for a plant crop of sugarcane under rainfed and irrigated environments in Brazil. Field Crops Research, v. 114, p. 351-360, 2009. MONTEIRO, L.A.; SENTELHAS, P.C. Sugarcane yield gap – Is it possible to determine it at national level with a simple agrometeorological model? Crop and Pasture Science, v. 68, n. 3, p. 272-284, 2017. SINGELS, A.; JONES, M.R.; VAN DER LAAN, M. Modelling impacts of stomatal drought sensitivity and root growth rate on sugarcane yield. In: INTERNATIONAL CROP MODELLING SYMPOSIUM, 2016, Berlin, Proceedings…, 2016, p. 292-293, 435p. SMITH, D.M.; INMAN-BAMBER, N.G.; THORBURN, P.J. Growth and function of the sugarcane root system. Field Crops Research, v. 92, p. 169–184, 2005. XAVIER, A.C.; KING, C.W.; SCANLON, B.R. Daily gridded meteorological variables in Brazil (1980–2013). International Journal of Climatology. n. 36, n. 6, p. 2644-2659, 2016.