Root length density (RLD) is a critical feature in determining crops potential to uptake water and nutrients, but it is difficult to be measured. No standard method is currently available for assessing RLD in the soil. In this study, an in situ method used for other crops for studying root length density and distribution was tested for sugarcane (Saccharum spp.). This method involved root intersection counting (RIC) on a Rhodic Eutrudox profile using grids with 0.05 × 0.05 m and modeling RLD from RIC. The results were compared to a conventional soil core-sampled method (COR) (volume 0.00043 m 3 ). At four dates of the cropping season in three tillage treatments (plowing soil, minimum tillage and direct planting), with eight soil depths divided in 0.1 m soil layer (between 0-0.6 and 1.6-1.8 m) and three horizontal distances from the row (0-0.23, 0.23-0.46 and 0.46-0.69 m), COR and RIC methods presented similar RLD results. A positive relationship between COR and RIC was found (R 2 = 0.76). The RLD profiles considering the average of the three row distances per depth obtained using COR and RIC (mean of four dates and 12 replications) were close and did not differ at each depth of 0.1 m within a total depth of 0.6 m. Total RLD between 0 and 0.6 m was 7.300 and 7.100 m m -2 for COR and RIC respectively. For time consumption, the RIC method was tenfold less time-consuming than COR and RIC can be carried out in the field with no need to remove soil samples. The RLD distribution in depth and row distance (2-D variability) by RIC can be assessed in relation to the soil properties in the same soil profiles. The RIC method was suitable for studying these 2-D (depth and row distance in the soil profile) relationships between soil, tillage and root distribution in the field. Key words: Brasil, root mapping, root study methods, trench-profile method Densidade de comprimento e distribuição de raízes de cana-de-açúcar a partir da contagem de intersecção de raízes na parede do perfil RESUMO: A densidade de comprimento de raízes (DCR) é uma característica importante para determinar o potencial de absorção de água e nutrientes das plantas, mas é difícil de ser medida. Nenhum método padrão está atualmente disponível para avaliar a DCR no solo. Neste estudo, um método in situ usado em outras culturas para estudo da densidade de comprimento e distribuições das raízes foi testado para a cana-de-açúcar (Saccharum spp.). O método envolveu contagem de intersecções de raízes (CIR) no perfil de um Latossolo Vermelho eutroférrico, usando grade com quadrículas de 0.05 × 0.05 m, modelizando a DCR a partir da CIR. Os resultados foram comparados com o método do trado cilíndrico (TRA) (volume de 0.00043 m -3 ). Em quatro épocas durante o ciclo em três manejos do solo (plantio convencional, cultivo mínimo e plantio direto), em oito profundidades divididas a cada 0.1 m (entre 0 -0.6 e 1.6 -1.8 m) e três distâncias horizontais em relação à linha de plantio (0 -0.23, 0.23 -0.46 e 0.46 -0.69 m), os métodos TRA e CIR apresentaram resultados...

2 profile in pearl millet (Pennisetum glaucum (L.) R. Br). Application to measure root 3 system response to water stress in field conditions Abstract 27Pearl millet, unlike other cereals, is able to withstand dry and hot conditions and plays an 28 important role for food security in arid and semi-arid areas of Africa and India. However, low 29 soil fertility and drought constrain pearl millet yield. One of the main targets to address these 30 constraints through agricultural practices or breeding is root system architecture. In this study, 31 in order to easily phenotype the root system in field conditions, we developed a model to 32 predict root length density (RLD) of pearl millet plants from root intersection densities (RID) 33 counted on a trench profile in field conditions. We identified root orientation as an important 34 parameter to improve the relationship between RID and RLD. Root orientation was notably 35 found to differ between thick roots (more anisotropic with depth) and fine roots (isotropic at 36 all depths). We used our model to study pearl millet root system response to drought and 37 showed that pearl millet reorients its root growth toward deeper soil layers that retain more 38 water in these conditions. Overall, this model opens ways for the characterization of the 39 impact of environmental factors and management practices on pearl millet root system 40 development. 41 43 Pearl millet (Pennisetum glaucum (L.) R. Br., syn. Cenchrus americanus (L.) Morrone) is a 44 cereal crop domesticated in the Western part of Sahel about 5,000 years ago [1]. It is well 45 adapted to dry tropical climate and low-fertility soils and therefore plays an important role for 46 food security in arid and semi-arid regions of sub-Saharan Africa and India. In these areas, 47 pearl millet is one of the most important sources of nutritious food [2, 3] and is the staple crop 48 for nearly 100 million people [4, 1]. Its grain is rich in protein, essential micronutrients and 49 calories. It is also gluten-free and has hypoallergenic properties [4]. In a context of climate 50 change leading to unpredictable weather patterns and rising temperatures in West Africa [5, 51 6], pearl millet could play an even more important role for food security because it can 52 withstand hot and dry conditions that would lead to the failure of other locally grown cereal 53 crops such as maize or sorghum. However, pearl millet lags far behind other cereals in terms 54 of breeding and its yield is low. The recent sequencing of a reference genome and about 1, 55 000 accessions [4] open the way for a new era of genomic-based breeding in pearl millet.56However, this will depend on the availability of phenotyping methods to characterize and 57 exploit the available genetic diversity and identify interesting target traits. 58Drought and low soil fertility are among the most important factors limiting pearl millet 59 yield. The root system is responsible for water and nutrient uptake, and root system 60 architecture is therefore a potential target ...

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