Chemical Ripening Research Articles

APPLICATION OF CHEMICAL RIPENERS MIXTURES THE TECHNOLOGICAL QUALITY AND AGRICULTURAL PRODUCTIVITY OF SUGARCANE

ABSTRACT The objective of this work was to evaluate the effect of applying mixtures of chemical ripeners on the technological quality and agricultural productivity of sugarcane. The experimental design consisted of randomized blocks arranged in split- split-plots with four blocks, the main plots being constituted by sugarcane varieties SP803280 and SP801842. The subplots consisted of the application of the following products with their respective mixtures: control - absence of ripener; Sulfometrom methyl + glyphosate; ethephon + glyphosate; glyphosate and compounds of organic carboxylic radicals + glyphosate. The sub-subplots were composed of evaluation times: 0; 15 and 30 days after applying the products. Samples from each plot were collected manually and sent to the laboratory for the determination of soluble Brix solids (% broth); Sucrose content in the broth - Pol (% broth); Reducing sugars (RS%); Total reducing sugars (TRS%); Fiber (%); Purity (%); Humidity (%) and Total recoverable sugar TRS (kg t-1). The plots were fully harvested and the stems were taken for weighing and for characteristics determination: Yield per hectare (TCH) and Yield of sugar per hectare (TAH). The SP803280 variety was more responsive to the use of mixtures of chemical ripeners. For the technological characteristics, sulfometurom methyl (0.02 kg ha-1) + glyphosate (0.15 L ha-1) presented the best results from 15 days after application. Mixtures of chemical ripeners did not increase the yields of stalks and sugar per area.

English

Sugarcane chemical ripening is aimed at accelerating the sucrose accumulation in the stems for harvesting when the climate conditions of crop year are hardly optimal for natural ripening. The study aims at determining the best response of sugarcane varieties to glyphosate ripening effect and the harvest delay after its application in Ferke 2 Sugar Bowl, Northern Cote d’Ivoire, in order to improve the technological qualities of canes at the early harvest season. Twenty plantations (700 ha) hosting two commercial varieties NCo376 and SP711406 were treated with glyphosate (360 emulsion concentrated) at 0.8 L/ha. For each plantation, two sample plots of 1 ha control and treated were determined. Those samples were analyzed to determine the sucrose gradient all along the stalks and monitor their technological qualities after 10, 15 and 20 days. As results, glyphosate improved sucrose content and the recoverable sugar of treated varieties. SP71-1406 was more sensitive than NCo376 with uniform qualities all along stalks after 20 days. Gains of 1.6% sucrose content and 1.5% recoverable sugar were obtained, compared to the control. So, the uppermost parts preservation of harvested stalks is justified and a sugar gain of 0.13 t/ha except those generated by the ripener. Key words: Glyphosate, ripener, technological quality, gradient, sucrose, recoverable sugar.

SUNFLOWER PLANT RESPONSE TO SIMULATED DRIFT OF GLYPHOSATE AND TRINEXAPAC-ETHYL

ABSTRACT Chemical ripeners are frequently used on sugarcane crops in order to increase profitability. However, the drift of these products to neighbouring fields can expose susceptible non-target plants, such as sunflower, to these agents causing indirect impacts on growth and development. Therefore, this study aimed to assess the toxicity characterize possible changes in the growth of sunflower plants exposed to simulated drift of the ripeners glyphosate and trinexapac-ethyl. For each ripener, the following doses were used: glyphosate (0 (control), 3.6, 7.2, 14.4, 28.8 and 86.4 g a.e ha-1) and trinexapac-ethyl (0, 3.12, 6.25, 12.50, 25 and 75 g a.i ha-1). The effects of these products on plant height, number of leaves, leaf area, stem diameter and dry matter (leaves, stem, flower, root, shoot and total) were evaluated. We also conducted a visual analysis of symptoms of phytotoxicity after exposure. The effects of the ripeners on sunflower plants varied depending on the type of agent used and the dose. Plants treated with glyphosate showed altered growth patterns, indicating high sensitivity of these plants to the herbicide. With increasing doses, glyphosate drift promoted lower growth and development of sunflower plants and negatively affected productivity. Nevertheless, trinexapac-ethyl drift, in the evaluated doses, did not affect sunflower plants.

Parâmetros tecnológicos e produtivos da cana-de-açúcar quando submetida à aplicação de maturadores químicos no início de safra

O uso de maturadores químicos é uma realidade no setor sucroenergético. O objetivo deste trabalho foi avaliar os parâmetros tecnológicos e produtivos da cana-de-açúcar, quando submetida à aplicação de maturadores químicos no início de safra. O delineamento experimental utilizado foi em blocos casualizados arranjados em parcelas subdivididas, com 4 repetições. As parcelas principais consistiram da aplicação dos seguintes produtos com suas respectivas dosagens: controle - sem aplicação; sulfometuron-metil 0,02 kg ha-1 + glyphosate 0,15 L ha-1; etephon 0,34 L ha-1 + glyphosate 0,15 L ha-1; glyphosate 0,35 L ha-1; compostos de radicais carboxílicos orgânicos 1,0 L ha-1 + glyphosate 0,15 L ha-1. As subparcelas foram constituídas de diferentes épocas de avaliação: 0, 15 e 30 dias após a aplicação dos produtos. As amostras foram colhidas manualmente e encaminhadas ao laboratório para determinação do brix, pol, açúcares redutores, açúcares redutores totais, fibra, pureza, umidade e açúcar teórico recuperável. Além disso, foram determinados os parâmetros produtivos: toneladas de colmos por hectare e toneladas de açúcar por hectare. Por fim, foram realizadas as análises dos teores de ácido chiquímico e ácido salicílico. A aplicação da mistura de maturadores químicos compostos de radicais carboxílicos orgânicos + glyphosate apresentou um incremento para os parâmetros tecnológicos da cana-de-açúcar aos 15 dias após a aplicação (DAA), seguido pelo tratamento com a aplicação de glyphosate aos 30 DAA.

Morpho-anatomical aspects and technological quality of saccharine sorghum submitted to plant regulators

Com o aumento na demanda de combustíveis renováveis, a indústria sucroenergética tem tido como desafio o aumento da produtividade agroindustrial, além da redução dos custos de produção. Atualmente, são escassos os relatos da utilização de reguladores vegetais na cultura do sorgo sacarino. O objetivo deste trabalho foi avaliar aplicação dos reguladores vegetais na qualidade tecnológica e aspectos morfoanatômicos do sorgo sacarino. O ensaio foi realizado na usina Cerradinho em Catanduva SP. As aplicações dos reguladores vegetais foram: etephon nas dosagens de 1,32, 0,66, 0,33 L ha-1, sulfometuron-methyl nas dosagens de 20, 10, 5 g ha-1, thiadizuron nas dosagens de 0,150, 0,100, 0,50 L ha-1, ethyl-trinexapac nas dosagens de 0,80, 0,40, 0,20 L ha-1 e controle. O experimento foi conduzido em Blocos Casualizados, no esquema de parcelas subdivididas com quatro repetições. Foram avaliadas as variáveis tecnológicas: pureza do caldo, açúcares redutores, açúcares totais recuperáveis, brix do caldo, pol do caldo, açúcares teóricos recuperáveis, fibra (%) e mensurados: espessura da epiderme da face adaxial (EAD); espessura da epiderme da face abaxial (EAB); diâmetro do esclerênquima (DE); espessura do mesofilo (MF); diâmetro dos vasos xilemáticos (DX) e diâmetro dos vasos floemáticos (DF). Para as características tecnológicas, os maturadores químicos sulfometuron-methyl e etephon nas doses 5 g ha-1 e 0,33 L ha-1, respectivamente, promoveram os melhores resultados a partir dos 37 dias após a aplicação. Para as características morfonatômicas, o maturador químico thiadizuron na dose 0,100 L ha-1 apresentou os melhores resultados aos 44 dias após a aplicação.

Evaluating the Effects of Chemical Ripening with Fluazifop-p-butyl on Sugarcane (Saccharum officinarum) Yield and Sugar Content

Ripening in sugarcane refers to an increase in sugar content on a fresh weight basis prior to commercial harvesting. Ripening is often prompted by use of chemicals and environmental cues such as moisture stress. The aim of this research was to determine the effects of Fluazifop- pbutyl, a chemical ripener on sugarcane yield and sugar content. The experiment was laid out as a Random Complete Block Design (RCBD) with five replications. Treatments were: Fluazifop- p- butyl (0.45 lha-1), drying off, Fluazifop- p- butyl (0.45 lha-1) + drying off and the control (no Dry off, no Fluazifop- p- butyl). The experiment was carried out at Triangle Estate which is located in the South East Lowveld of Zimbabwe from March 2012 to May 2012. Data on sugarcane yield, sugar quality (Pol % and ERC %) and sugar yield was collected 56 days after establishment of the experiment. Analysis of variance was done on yield and quality data using Genstat 14th edition. Results showed that there were significant differences (P = 0.05) among treatments on sugarcane yield, sugar yield, Pol% and ERC%. The sugarcane yield was highest for the control where no ripener was used. Fluazifop- p- butyl treatment attained 13.9% lower sugarcane yield relative to the control. Application of Fluazifop- p- butyl resulted in the highest sugar yield which was 35.6% higher than that of the control where no ripener was used. A combination of Fluazifop- p- butyl and Dry of resulted in the highest Pol % and highest ERC %. It can be concluded that Fluazifop- p- butyl is effective in increasing sugar yield although it results in a reduction in sugarcane yield. Combining Fluazifop- p- butyl with Dry off results in increased Pol% and ERC%. There is need for further studies to determine the optimum period from spraying Fluazifop- p-butyl to harvesting of sugarcane as this was only done at the end of the drying-off period.

Sugarcane Yield and Technological Ripening Responses to Chemical Ripeners

The present investigation was carried out in Khuzestan province of Iran to evaluate the effects of chemical ripeners on the advancement of cane maturity (var. CP57-614) during incline phase. Three chemicals viz. Ethephon (2-Chloroethyl phosphoric acid), Glyphosate, and Fitomas M (a growth regulator) were applied as foliar spray on the crop using a small aircraft. The result showed that application of glyphosate increased brix, pol%, fiber, and recoverable sugar; however, its application reduced cane length and invert sugars and also showed marginal decline in the cane yield. The improvement in cane quality was more pronounced compared to the reduction in cane yield. Ethephon application had no impact on cane tonnage, and showed marginal improvement in pol per cent (3.3 %) and recoverable sugar (3.4 %) compared to untreated control. Fitomas-M had no effect on cane tonnage; on the contrary, it showed decline in pol%. Based on the large-scale trials done in Khuzestan province, it was demonstrated that 0.5 l ha−1 of glyphosate increased recoverable sugar to the extent of 10.60 % indicating that this treatment was most suitable for increasing sucrose content during incline period of crop maturity or early stages of harvest.

Mass spectrometry imaging reveals new biological roles for choline esters and Tyrian purple precursors in muricid molluscs.

Despite significant advances in chemical ecology, the biodistribution, temporal changes and ecological function of most marine secondary metabolites remain unknown. One such example is the association between choline esters and Tyrian purple precursors in muricid molluscs. Mass spectrometry imaging (MSI) on nano-structured surfaces has emerged as a sophisticated platform for spatial analysis of low molecular mass metabolites in heterogeneous tissues, ideal for low abundant secondary metabolites. Here we applied desorption-ionisation on porous silicon (DIOS) to examine in situ changes in biodistribution over the reproductive cycle. DIOS-MSI showed muscle-relaxing choline ester murexine to co-localise with tyrindoxyl sulfate in the biosynthetic hypobranchial glands. But during egg-laying, murexine was transferred to the capsule gland, and then to the egg capsules, where chemical ripening resulted in Tyrian purple formation. Murexine was found to tranquilise the larvae and may relax the reproductive tract. This study shows that DIOS-MSI is a powerful tool that can provide new insights into marine chemo-ecology.

Chemical ripening of sugarcane with trinexapac-ethyl (Moddus®) — Mode of action and comparative efficacy

Chemical ripeners cause growth suppression, thus increasing sucrose accumulation in sugarcane by lowering the growth sink demand for sucrose. Trinexapac-ethyl (Moddus®), the most recent chemical to be introduced as a ripener with a hormonal mechanism, inhibits production of the plant hormone gibberellic acid, which leads to restriction of internode elongation. This study reports novel findings on a dual mode of action, by which Moddus® affects growth processes in both the stalk and leaf canopy above a certain concentration, and how this influences ripening efficacy. In addition the efficacy of Moddus® is compared to Ethephon®, the other ripener with a hormonal mechanism. An irrigated field trial was planted to variety N32 at the South African Sugarcane Research Institute’s research station in Pongola, South Africa. The plant and subsequent three ratoons were used as experimental crops and harvested in April of each year. Replicated treatment plots consisted of 6 cane rows, 16m long and spaced 1.4m apart. Treatments comprised an unsprayed control, Ethephon® applied according to standard practise, and Moddus® applied at three dosages. Products were applied with CO2-pressurised equipment and a hand-held overhead spray boom. Measurements on the stalks (length, individual internode elongation and juice quality) and leaves (green and dead leaf mass per stalk) were conducted at intervals until harvest. At harvest the cane and sugar yield was determined for each treatment. A novel finding was that Moddus®, above a certain concentration, ripened the crop through a dual mode of action involving restriction of both internode elongation and leaf growth. Characterisation of effects on individual internode elongation and mass of the green leaf canopy, coupled to yield data, provided insights to be considered in future when attempting to explain varietal differences in response to Moddus®. The easy-to-measure plant processes identified in this study as sensitive indicators of ripening efficacy might enable initial pot-based screening of large numbers of varieties for responsiveness to Moddus®, before embarking on more time-consuming and expensive field-based testing. The data acquired in this study could also be used in attempts to simulate Moddus®-induced ripening with mechanistic sugarcane crop models.

Trinexapac-Ethyl and Sulfometuron-Methyl Selectivity to Young Eucalyptus Plants

Trinexapac-ethyl and sulfometuron-methyl are the most widely used ripeners in sugarcane. The application is performed by airborne spraying. Thus, if weather conditions are unfavorable, spray drift to neighboring areas may occur. The objective of this study was to assess the selectivity of the plant growth regulators trinexapac-ethyl and sulfometuron-methyl, used as sugarcane ripeners, to eucalyptus (Eucalyptus urograndis) young plants. The experiment was installed in an eucalyptus commercial yield area, in the municipality of Tambaú, state of São Paulo, Brazil, and arranged in a 2 x 8 factorial design in randomized blocks with four replications. The treatments studied were trinexapac-ethyl and sulfometuron-methyl, sprayed in eight doses, 0; 1.0; 2.5; 5.0; 10; 25; 50 and 100% of the dose used in sugarcane as ripeners (200 g ha-1 of trinexapac-ethyl and 15 g ha-1 of sulfometuron-methyl). Chemical ripeners were applied on eucalyptus plants with 48 cm in height on average; 10.1 branches; 4.5 mm of stem diameter and 44.3 cm of crown diameter, at 46 days after seeding. Trinexapac-ethyl was selective to eucalyptus and stimulated crown diameter growth. At higher doses, sulfometuron-methyl promoted severe noticeable injuries in eucalyptus plants, such as apical bud death. However, during the assessment period the plants recovered and the visual symptoms of phytotoxicity and growth alterations were not observed at 60 days after application. The plant growth regulators trinexapac-ethyl and sulfometuron-methyl were selective to eucalyptus young plants.

Evaluation of Trinexapac-ethyl (Moddus®) as a New Chemical Ripener for the South African Sugarcane Industry

Although information from Brazil and Australia indicate that trinexapac-ethyl (Moddus®) is an excellent new sugarcane ripener, there is no information on the response of South African varieties to this chemical. The objective of this investigation was to establish the ripening potential of this chemical in a local variety and to compare responses with current industry standards, 2-chloroethyl phosphonic acid (Ethephon®) and fluazifop-p-butyl (Fusilade Forte®). Evaluation was conducted in an irrigated plant and first ratoon crop of variety N32 at Pongola, South Africa. The field trial was laid out as a complete randomised design with five replicates per treatment. The nine treatments comprised: (a) untreated control, (b) Ethephon® (1.5 L/ha) applied 84 days before harvest (DBH), (c) Fusilade Forte® (0.2 L/ha) applied 43 DBH, (d) Moddus® at three rates (0.8, 1 and 2 L/ha) applied 70 DBH, (e) Ethephon® (1.5 L/ha) and Fusilade Forte® (0.2 L/ha) applied in combination 84 and 43 DBH, and (f) Moddus® (0.8 and 1 L/ha) and Fusilade Forte® (0.2 L/ha) applied in combination 70 and 43 DBH. The various ripener treatments improved estimated recoverable crystal (ERC) yields in the 12-month old crops by between 1.6 and 4.9 t/ha when compared with the control. Moddus® applied at 0.8 and 1 L/ha achieved similar improvements as Fusilade Forte® and Ethephon®, but at 2 L/ha outperformed the latter two ripeners by up to 1.9 t ERC/ha. Best ERC yield responses were achieved in the three combination treatments. However, the Moddus®—Fusilade Forte® combination treatments outperformed the standard Ethephon®—Fusilade Forte® combination treatment by up to 1 t ERC/ha. These results indicate that Moddus® is an effective sugarcane ripener under South African high-potential irrigated conditions and that improved in ERC yields exceeding those obtained with current industry standards might be possible.

Herbicides as Ripeners for Sugarcane

Chemical ripening of sugarcane is an important component to profitable sugar production in the United States as well as other sugarcane industries throughout the world. Harvesting of sugarcane often begins before the sugarcane reaches the desirable maturity level. This is especially true in the Louisiana sugarcane industry where the window for harvesting is limited because of the risk of freezing temperatures encountered in a temperate climate. Research on the application of chemicals, mostly of herbicide origin, to enhance sucrose accumulation (ripening) or limit flowering to conserve stored sucrose has been conducted for more than 60 yr. The only sugarcane ripener currently registered for use in the United States is glyphosate applied before harvest. The herbicide fluazifop is used as the primary ripener of sugarcane in South Africa. The herbicides glyphosate, fluazifop, and sulfometuron-methyl and the growth regulators ethephon and trinexapac-ethyl are registered for use in Brazil. There is a continuing need to evaluate sugarcane ripeners to increase the utility of currently registered ripeners and to find additional ripeners for use by sugarcane industries. The need for alternatives to glyphosate is especially critical before a glyphosate-tolerant sugarcane can be utilized to improve control of problematic weeds.

Efeito dos Maturadores Químicos na Cultura da Cana-de-Açúcar (Saccharum spp).

SUMMARY: The maturation of the sugarcane is a physiological process that involves the synthesis of sugars in the leaves, translocation of the products formed and storage of sucrose in the stem. The different chemical ripeners differ not only in formulating but also in the time between application and harvest and weather conditions required. This review aimed to make a survey of the effect of chemical ripeners in the sugarcane (Saccharum spp). The specific methodology used sought to understand the publications on the effect of chemicals applied to matured crop of sugarcane. Were matured addressed the various chemicals applied to the culture of sugarcane, and the effects of these, the concept of maturity, flowering and the use of inhibitors and the results and recommendations on the use. It was concluded that the chemicals ripeners in the sugarcane enabled improved productivity when used technically, combining increased plant growth and maximum accumulation of sucrose.

EFEITO DOS MATURADORES QUÍMICOS NA CULTURA DA CANA-DE-AÇÚCAR (Saccharum spp)

The maturation of the sugarcane is a physiological process that involves the synthesis of sugars in the leaves, translocation of the products formed and storage of sucrose in the stem. The different chemical ripeners differ not only in formulating but also in the time between application and harvest and weather conditions required. This review aimed to make a survey of the effect of chemical ripeners in the sugarcane (Saccharum spp). The specific methodology used sought to understand the publications on the effect of chemicals applied to matured crop of sugarcane. Were matured addressed the various chemicals applied to the culture of sugarcane, and the effects of these, the concept of maturity, flowering and the use of inhibitors and the results and recommendations on the use. It was concluded that the chemicals ripeners in the sugarcane enabled improved productivity when used technically, combining increased plant growth and maximum accumulation of sucrose.

Effects of Chemical Ripeners on Photosynthetic Characteristics of Pods and Rapeseed Quality and Yield

We investigated the effects of chemical ripeners Diguat and Roundup on photosynthetic rate, gas exchange parameters and chlorophyll content in pods, 1000-grain weight and yield and oil content through gas exchange measuring technology during the latest stage of pod growth. The ripener Diquat, with a good effect on accelerating pods ripening, damaged pod peel chlorophyll seriously, decreased photosynthetic rate, and light-energy utilization efficiency rapidly, so that the 1000-grain weight, yield and quality decreased largely, which sensitively depends on the Diquat content. In comparison, the ripener Roundup, with a slow ef- fect on pods ripening, had a less harm on pod growth and a higher photosynthetic rate, so that the yield and quality of grains were higher. Our investigations disclosed a close relationship of grain yield and oil content with Pn and chlorophyll content, proving the importance of utilization efficiency of light energy in the latest stage of pods ripening on the grain yield and oil accumulation. In production, we recommend an appropriate ripener recipe of 0.1% Diguat or 0.8% Roundup for accelerating pods ripening with a less loss of the grain yield.

Registration of ‘HoCP 00‐950’ Sugarcane

‘HoCP 00‐950’ (Reg. No. CV‐135, PI 654823) sugarcane (a complex hybrid of Saccharum officinarum L., S. spontaneum L., S. barberi Jeswiet, and S. sinense Roxb. amend. Jeswiet) was selected and evaluated by the USDA‐ARS, working cooperatively with the Louisiana State University AgCenter, and the American Sugar Cane League, Inc. It was released to growers in Louisiana in April 2007. In 67 machine‐harvested trials on light‐ and heavy‐textured soils from 2004 to 2007 (plant‐cane through third‐ratoon crop) averaged over nine southern Louisiana locations, HoCP 00‐950 produced 5% more sugar and had 6% higher sugar content than the industry standard, ‘HoCP 96‐540’. In plant‐cane and ratoon‐crop maturity tests harvested in 2007, HoCP 00‐950 had significantly higher sugar content than HoCP 96‐540 across all harvest dates, with 35% higher sugar content at the outset of the harvest season (late September). HoCP 00‐950 is resistant to brown rust (Puccinia melanocephala), smut (Ustilago scitaminea), leaf scald (Xanthomonas albilineans), and mosaic diseases. It is susceptible to the sugarcane borer (Diatraea saccharalis) and should not be planted in areas where pesticide use is restricted. The early maturity characteristic of HoCP 00‐950 provides growers with a variety that can produce profitable sugar yields early in the milling season without the need to apply a chemical ripener.

Efeito da aplicação de maturadores químicos na cultura da cana de açúcar (<em>Saccharum</em> spp.) Variedade SP81-3250

Sugarcane is one of the most important grass crops. This study evaluated the effects of chemical ripeners on the sugarcane variety SP81-3250 in terms of technological quality. The experiment was arranged in randomized blocks with split split-plots. Main treatments were: 1) Control; 2) Aminolon Maduracion, at a rate of 0.7 L of commercial product (c.p.) ha -1 ; 3) Aminolon Maduracion, at a rate of 1.0 liter of c.p. ha -1 ; 4) Aminolon Maduracion, at a rate of 1.3 liter of c.p. ha -1 ; 5) Trinexapac-ethyl (Moddus), at a rate of 0.8 liter of c.p. ha -1 . Secondary treatments were the sampling dates: 10 days before application (- 10 d.a.a.); 11; 46; 71; 100 and 117 d.a.a. (days after application). Ripeners differently affected the technological parameters, and trinexapac-ethyl showed the best behavior, followed by Aminolon (0.7 L of c.p. ha -1 ). The best results were found at the 3 rd and 4 th sampling dates, 46 and 71 days after application, respectively

Chemical ripeners increase early season sugar content in a range of sugarcane varieties

Ripening in sugarcane refers to an increase in sugar content on a fresh weight basis before commercial harvest. Certain chemicals are applied to cane in commercial fields in some countries to accelerate ripening and improve profitability of sugar production. However, responses have usually been reported to be variety and environment specific. We examined changes in the sucrose content in the juice extracted from 43 Australian sugarcane (Saccharum spp. hybrid) varieties in response to 4 ripener treatments in the Burdekin region in northern Queensland over 2 years. The 4 treatments applied were ethephon (as Ethrel®) + fluazifop-P butyl (as Fusilade®), Fusilade® alone, glyphosate (as Weedmaster® Duo), and haloxyfop-R methyl (as Verdict®). These treatments were applied in March–April each year and compared with an untreated control. Of particular interest was whether economic responses are possible for Australian varieties harvested in the May and June period when sugar content in cane is usually low. Increases in sucrose (measured by pol) levels in cane juice were observed after combined application of Ethrel + Fusilade (E+F) and after application of glyphosate, although the result for the latter varied between years. These results suggest that opportunities exist in the Australian industry to improve the profitability of early-harvested sugarcane crops, but further research is required to quantify effects on cane yield and responses in diverse environments.

Improving biomass production and partitioning in sugarcane: theory and practice

Sucrose yields in sugarcane ( Saccharum spp.) could be improved by increasing the efficiency of biomass production per unit of intercepted radiation and/or by increasing the fraction of total biomass partitioned to stalk sucrose, or both. In theory, this could be achieved by optimally matching the physiology of genotypes to the driving environmental conditions. Quantitative knowledge of the subtle effects of climate and genotype is therefore required to optimise cultivar choice, time of harvest, irrigation and chemical ripening. The objective of this paper is to review existing knowledge of the effect of time of harvest and cultivar on the assimilation and partitioning of biomass in sugarcane by comparing modelling theory and published literature with observations from selected experiments conducted at Pongola, South Africa. Simulations were compared with observations for well-watered crops harvested at different times of the year at Pongola, South Africa. Crops started in April and May seem to have higher radiation use efficiencies than other crops, thereby compensating for lower interception of radiation during this time of the year. Winter-harvested crops partitioned a smaller fraction of final biomass to leaves and more to stalks than summer-harvested crops. This trend was not simulated by the Canegro model. Simulations were partially improved by refining the model to account for temperature control of photosynthesis and respiration. The observed seasonal peak of stalk sucrose content also occurred later than simulated, while the observed decrease in sucrose content from January to April could not be reproduced by the model. These shortcomings have serious implications for the relevance of the model as a tool for identifying crop improvement and management strategies. However, the Canegro model successfully mimicked partitioning of assimilate to stored sucrose using two cultivar parameters. Results suggest that there is scope for improving yields but that the optimisation process should include all components of the sucrose production process in sugarcane, including radiation capture, net photosynthetic efficiency and stalk partitioning. Sufficient understanding of the interactions between these components is lacking. There is a need for models to distinguish between photosynthesis and respiration and the strong dependence of both on temperature should be taken into account. Sinks for leaf, stalk structure and sucrose need to be considered separately to adequately understand the effect of temperature on partitioning.

Chemical ripening of sugarcane: global progress and recent developments in China

Chemical ripening of sugarcane is a well established practice to enhance sucrose content in many sugarcane growing countries. Chemical ripeners such as Ethephon, Glyphosate analogues, Fusilade Super, Gallant Super are being used in large scale sugarcane plantations. The gains in sucrose content in sugarcane have been reported from 0.5-2.0 units, depending upon variety-weather-ripener interaction. In mainland China, many chemicals with ripeners like properties such as Lanthanium rich rare earth mixture, lime water, potassium di hydrogen phosphate etc. have been tried. Duoxiaohao- a product consisted of multiple nutrient elements also showed good results in improving plant growth and sugar accumulation in sugarcane. However, the best results have been obtained with glyphosate-borate complex which was effective even under water deficit stress and did not affect sprouting of subsequent ratoon crop. The average improvement in pol% cane was over 1.0 unit. Due to its commercial benefits, it has been popularized in large scale of sugarcane plantations in Guangxi Province and at present about 20,000 hectares have been brought under chemical ripening using glyphosate-borate aerial spray.