SuMMarySugarcane, which involves the use of agricultural machinery in all crop stages, from soil preparation to harvest, is currently one of the most relevant crops for agribusiness in Brazil. the purpose of this study was to investigate soil physical properties and root growth in a eutroferric red oxisol (latossolo Vermelho eutroférrico) after different periods under sugarcane. the study was carried out in a cane plantation in rolândia, Paraná State, where treatments consisted of a number of cuts (1, 3, 8, 10 and 16), harvested as green and burned sugarcane, at which soil bulk density, macro and microporosity, penetration resistance, as well as root length, density and area were determined. results showed that sugarcane management practices lead to alterations in soil penetration resistance, bulk density and porosity, compared to native forest soil. these alterations in soil physical characteristics impede the full growth of the sugarcane root system beneath 10 cm, in all growing seasons analyzed. index terms: Saccharum spp., compaction, monoculture. A cana-de-açúcar é, na atualidade, uma reSuMo: PROPRIEDADES FÍSICAS DE SOLO E CRESCIMENTO RADICULAR DE CANA-DE-AÇÚCAR EM UM LATOSSOLO VERMELHO

Root length density (RLD) is a key factor in crop functioning. A field method was developed to quantify RLD of sugarcane from root intersection density (RID) taking root orientations into account. RIDs were observed on three perpendicular soil planes and RLD was measured for the enclosed volume. RID and RLD of thick and fine roots were measured separately. These measurements were replicated at different ages and sites to test models describing RLD according to RID. Fine roots were nearly isotropic and thick roots had a preferential orientation, i.e. horizontal near the surface and becoming progressively vertical in deeper horizons. Relationships in thick roots were modelled according to CO t : RLD t = RID t . CO t (CO t : root orientation coefficient, ranged from 1.3 to 4.9 for thick roots). For fine roots ( f ), CO f =2. This theoretical model led to differences between measured and calculated RLD. The ratio between measured and calculated RLD f (CE f ) increased from 1 to 3 with RID f . CE f was introduced as an additional coefficient in the model: RLD f =2. NI f . CE f . Intermediate results were obtained for all ( a ) roots: CO a and CE a were both dependent on RID a , therefore: RLD a = NI a . CO a . CE a . The models were validated with independent datasets from Brazil and France. These allowed a more robust prediction of RLD than direct regressions between RID and RLD. They may estimate RLD from RID in soil profiles by root mapping while taking RLD spatial variability into account. Keywords Root modelling . Root orientation . Root architecture . Saccharum spp. . Trench-profile method Abbreviations CO Geometric coefficient to calculate RLD from RID CE Experimental coefficient to calculate RLD from RID DAP Days after planting d root diameter (mm) DAR Days after ratoon MD Methodology development (of models) MV Methodology validation (of models) RID Root intersection density (per m 2 ) RLD Root length density (m m −3 ) Plant Soil

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...

Resumo -O objetivo deste trabalho foi avaliar o efeito de diferentes quantidades de palhada sobre o sistema radicular e a produtividade da cana-de-açúcar (Saccharum officinarum), de primeira e segunda soqueiras, em Latossolo Vermelho eutroférrico. Seis tratamentos foram avaliados: 0, 5 (25%), 10 (50%), 15 (75%) e 20 Mg ha -1 (100%) de palhada e cana-queimada, na primeira e segunda soqueiras. Utilizou-se a cana-de-açúcar 'SP80-1816'. Avaliou-se a massa de raízes a 0,45 e 0,75 m de distância da linha de plantio, até 0,60 m de profundidade. Na primeira soqueira, os tratamentos com 50, 75 e 100% de palhada proporcionaram maior massa radicular até 0,20 m de profundidade, em comparação aos tratamentos cana-queimada, 0 e 5 Mg ha -1 (25%) de palhada. Os tratamentos com 50 e 75% de palhada proporcionaram produtividades 43% maiores do que a da cana-queimada (110 Mg ha -1 ). O tratamento com 10 Mg ha -1 (50%) foi suficiente para proporcionar aumento da massa radicular e da produtividade da cana-de-açúcar. O sistema radicular e a produtividade da cana-de-açúcar são favorecidos pela mudança do sistema de colheita de cana-queimada para o de cana sob palhada.Termos para indexação: Saccharum officinarum, biomassa, cana crua, colheita mecanizada, enraizamento, manejo da palhada, produção agrícola. Root system and productivity of sugarcane ratoon associated to different quantities of strawAbstract -The objective of this work was to evaluate the effect of different amounts of straw on the root system and productivity of sugarcane (Saccharum officinarum), of first and second ratoons, in an Oxisol. Six treatments were evaluated: 0, 5 (25%), 10 (50%), 15 (75%), and 20 Mg ha -1 (100%) straw and burned sugarcane of the first and second ratoons. 'SP80-1816' sugarcane was used. Root mass at 0.45 and 0.75 m away from the row, and up to 0.60 m deep was evaluated. In the first ratoon, treatments with 50, 75 and 100% straw provided greater root mass up to 0.20-m depth, in comparison to treatments of burned sugarcane, and 0 and 5 Mg ha -1 (25%) straw. The treatments with 50 and 75% straw had 43% higher yields than burned sugarcane (110 Mg ha -1 ). The treatment with 10 Mg ha -1 straw (50%) was sufficient to provide increased root mass and productivity of sugarcane. The root system and the productivity of sugarcane are favored by the change of burned-sugarcane harvesting system to sugarcane under straw.

O objetivo deste trabalho foi verificar se o sistema de preparo do solo afeta a distribuição e o acúmulo de matéria seca (MS), carbono (C) e nitrogênio (N) das raízes de soja (Glycine max) e milho (Zea mays), em um Latossolo Vermelho distroférrico muito argiloso. A amostragem das raízes até 1 m de profundidade foi feita com anéis volumétricos. A distribuição em profundidade e o acúmulo de MS, C e N das raízes não foram influenciados pelo preparo do solo. A densidade de comprimento de raízes na camada de 0-0, 10 m foi de 0,7 a 1,4 cm cm-3 em soja, e de 1,2 a 1,6 cm cm-3 em milho, e decresceu nas demais camadas. O acúmulo de MS das raízes foi de 1,94 a 2,01 Mg ha-1 em soja, e de 2,50 a 3,79 Mg ha-1 em milho. Houve acúmulo de 0,61 a 0,63 Mg ha-1 de C e de 36,9 a 38,2 kg ha-1 de N em soja, e de 0,72 a 1,10 Mg ha-1 de C e de 18,78 a 28,48 kg ha-1 de N em milho. Independentemente do sistema de preparo do solo, 80% das raízes situam-se entre 0,43 e 0,54 m de profundidade em soja, e entre 0,40 e 0,46 m em milho.

Sugarcane straw mulch left in the field after its mechanical harvest has become very valuable raw material for second generation ethanol and bioelectricity production. However, little information is available on how much straw mulch is needed to be left in the field so that agricultural productivity is not affected and high sustainability is provided for the bioenergy production system. The objective of this work was to evaluate the productivity and industrial quality of sugarcane after five years of cultivation when different amount of straw mulch is removed from the field. The experiment was installed in clay texture Eutroferric Red Latosol (Oxisol). Six treatments were evaluated: 0%, 25% (5 t ha −1), 50% (10 t ha −1), 75% (15 t ha −1), 100% (20 t ha −1) of straw mulch and burnt cane harvesting (where 100% of the straw mulch was burned). Evaluated parameters included sugarcane productivity (tons/hectare) and its industrial quality (Pol, soluble solids (°Brix), apparent purity and total sugars (TS)). Productivity was calculated at the end of the cycle whereas industrial quality parameters were evaluated during three phases i.e. 180, 240 and 350 days after cutting (DAC). Straw mulch of 50 and 75% were statistically at par with each other but resulted in higher sugarcane production with 47% more productivity as compared to 0 and 25% of straw mulch as well as burned cane harvesting. Straw mulch didn't affect the industrial quality; however, higher sugar production was supported by higher agricultural productivity, under low moisture condition. It is possible to remove 50% of straw mulch from the field for the production of second generation ethanol or bioelectricity, without any damage to the crop.

Field studies on citrus roots are important for genetic selection of cultivars and for management practices such as localized irrigation and fertilization. To characterize root systems of six rootstocks, taking into consideration chemical and physical characteristics of a clayey Typic Hapludox of the Northern State of Paraná, this study was performed having as scion the 'IAC-5 Tahiti' lime [Citrus latifolia (Yu. Tanaka)]. The rootstocks 'Rangpur' lime (C. limonia Osbeck), 'Africa Rough' lemon (C. jambhiri Lush.), 'Sunki' mandarin [C. sunki (Hayata) hort. ex Tan.], Poncirus trifoliata (L.) Raf., 'C13' citrange [C. sinensis (L.) Osb. x P. trifoliata (L.) Raf] and 'Catânia 2' Volkamer lemon (C. volkameriana Ten. & Pasq.) were used applying the trench profile method and the SIARCS® 3.0 software to determine root distribution. 'C-13' citrange had the largest root system. 'Volkamer' lemon and 'Africa Rough' lemon presented the smallest amount of roots. The effective depth for 80 % of roots was 31-53 cm in rows and 67-68 cm in inter-rows. The effective distance of 80 % of roots measured from the tree trunk exceeded the tree canopy for P. trifoliata, 'Sunki' mandarin, and 'Volkamer' and 'Africa Rough' lemons.

Due to mechanical harvesting large amount of straw is left in the field which implicates modification throughout the agriculture environment. This straw is beneficial for both soil and plant. However, there is no information about the sufficient quantity which can be used to achieve such effects and also whether it can be used in other sectors like electricity and ethanol production. Therefore, a research was designed with the objective to evaluate the effect of different amounts of straw on the development and productivity of sugarcane during the first and second ratoons. Treatments used in the experiment included: burned cane, 0%, 25%, 50%, 75% and 100% (20 t ha −1) of sugarcane straw left on the soil surface. The tested variables included leaf area index (LAI), number, diameter, length and production of stems. Plants were evaluated at 60, 120, 180, 240 and 370 days after harvest (DAH) for the first ratoon and at 60, 120, 180, 240 and 270 DAH for the second ratoon. Replacing burned cane harvest system for soil management with straw promotes the development and productivity of sugarcane ratoons. Field managements with burned cane, total removal of the straw, or keeping 25% of straw result in low number of tillers, leaf area index, stem diameter and productivity of sugarcane ratoons, under water stress conditions. Whereas keeping 50% of straw mulch is enough to improve the growth and yield of sugarcane with drought occurrences, while the remaining 50% can be used for second generation of ethanol production or electricity without damaging the crop yield.