Trash Blanket Research Articles

Simulando a resposta da produtividade da cana-de-açúcar a reposições da ETc e quantidade da palhada no Brasil

ABSTRACT Determining the proper crop water requirement associated with the optimum amount of green cane trash blanket (GCTB) on the soil is one of the most discussed issues for sugarcane growers. In this context, this research aimed to evaluate the effects of different amounts of GCTB and ETc replacement scenarios on sugarcane yields across key producing regions in Brazil using the agricultural production systems simulator (APSIM). The sugarcane APSIM (APSIM-Sugar) was parameterized and validated for sugarcane in Brazil, compared to both 100% GCTB cover and bare soil, both fully irrigated. After validation through field data, the APSIM-Sugar model was used to simulate 25 different scenarios with varying GCTB amounts and irrigation demands in 12 regions of Brazil for a 30-year period to estimate stalk yield. Overall, modeled and field data agreed very well regarding soil moisture and biometric and physiological variables, achieving strong modeling efficiency. For most producing regions of Brazil, interaction between the factors did not increase stalk yield significantly, and up to 50% of ETc replacement resulted in the highest increases in stalk yield, with the greatest improvement between 0-25%, producing an average increase of 30 Mg ha-1 per year. The recommended amount of GCTB is at least 5.50 Mg ha-1, taking into account soil health and the need for biofuel generation.

Impacts of sugarcane (Saccharum sp.) soil and fertiliser management practices on nutrients and sediment in plot-scale runoff from simulated rainfall

Runoff of nutrients and sediment from agricultural catchments can impair the health and resilience of aquatic ecosystems in receiving waterbodies. The sugarcane (Saccharum sp.) industry in Australia has adopted strategies to improve farm runoff water quality. Rainfall simulation trials were conducted to quantify the relative effectiveness of some sugarcane soil and fertiliser management practices on nutrient and sediment loss in runoff. The trials were conducted within the Herbert River catchment in the Wet Tropics of Queensland. Simulated rainfall (~76 mm h–1) was used to generate runoff from 1.70 m2 plots in first ratoon sugarcane on well-drained Ferralsols at Abergowrie and from 1.55 m2 plots in sugarcane planted into furrows and mound beds on an imperfectly drained Luvisol at Trebonne. At Abergowrie, the practices studied were; crop residue retention after harvest (green cane trash blanketing), applying a liquid rather than a granular fertiliser, and applying fertiliser to the sub-surface rather than to the surface on ratoon phase sugarcane. At Trebonne, sub-surface fertiliser placement was studied on plant cane and after varying amounts of time and repeated rainfall after fertiliser application. Comparisons were made with a similar study in plant cane at Macknade. Particulate nitrogen (N), particulate phosphorus (P), and suspended sediment losses in runoff were reduced by crop residue retention, which was expected. Dissolved inorganic N (DIN) loads (but not concentrations) were also reduced by residue retention. Dissolved inorganic N and filterable reactive P concentrations in runoff were reduced by sub-surface fertiliser placement, as expected, and by the liquid fertiliser that was studied. In contrast to expectations, DIN concentrations increased in mound beds (but not in furrows) with increasing time and rainfall after fertiliser application. The increase was attributed mainly to increases in soil mineral N and runoff volume. The practice that was most effective at reducing DIN loads in runoff (64–85% reduction) was sub-surface rather than surface placement of fertiliser.

Ten years of monitoring dissolved inorganic nitrogen in runoff from sugarcane informs development of a modelling algorithm to prioritise organic and inorganic nutrient management

Reducing nitrogen (N) losses from cropping systems to aquatic ecosystems is a global priority. In Australia, N losses from sugarcane production in catchments adjacent to the Great Barrier Reef (GBR) are threatening the health of this World Heritage-listed coral reef ecosystem. N losses from sugarcane can be reduced by improving fertiliser management. However, little is known about the contribution of organic sources of N, such as mill mud. We used more than 10 years of data from two of the main Australian sugarcane regions, a high (Wet Tropics) and moderate (Mackay Whitsundays) rainfall area, to calibrate and validate a model to predict dissolved inorganic nitrogen (DIN) losses in runoff from both inorganic and organic fertilisers. DIN losses in runoff were well simulated (RMSE = 0.37 and 2.0 kg N ha−1 for the Wet Tropics and Mackay Whitsunday regions, respectively). Long-term simulations of rate and fertiliser deductions to account for N from organic sources showed that adopting best management practices for organic fertiliser (applying ≤50 wet t ha−1 mill mud) can significantly reduce DIN in runoff losses compared with applications of 150 wet t ha−1. Simulations of typical farmer practices in relation to fallow management (bare fallow vs. legume fallow) and organic fertiliser placement (buried in a fallow but surface applied to a green cane trash blanket in ratoons) showed that inorganic fertiliser rates need to be adjusted to account for N inputs from both mill mud and legume crops. Rates of application of organic N had a larger impact on DIN runoff losses than placement or timing of application. This work presents a DIN in runoff modelling algorithm that can be coupled with nitrogen models readily available in agricultural models to assess the impact of nutrient management on the quality of water leaving agricultural systems.

Global sensitivity and uncertainty analysis of a sugarcane model considering the trash blanket effect

The deterministic approach in crop modeling simplifies uncertainty present in the environment using a unique parameter set. In practice, this uncertainty is seen in the variability of data collected in a field experiment. One way to exploit this uncertainty is to use the stochastic approach, by inserting the range of plausible variability into the simulation’s parameters and inputs. This study aims to evaluate the ability of a process-based crop model to simulate the uncertainty of a sugarcane field. We employed the recently updated version of SAMUCA model to simulate the sugarcane growth and development in a 4-year field experiment, where the crop was grown under the effect of green cane trash blanket (GCTB) and bare soil (Bare). To analyze the effect of genotype and soil variability on output variables, a stochastic approach was applied to the corresponding parameters of the SAMUCA model. A global sensitivity analysis was utilized to prioritize and identify the most important parameters to explain the model uncertainty. Then, the uncertainty was analyzed in three different ways: uncertainty analysis only for genotype parameters (UG), uncertainty analysis only for soil parameters (US) and the analysis of both soil and genotype parameters (UGS). We quantified the variability of the stochastic simulation by the ratio between the average of the standard deviation of the simulations and the average of the standard deviation of the observed data. The variability observed in the field is not fully explained by the hydraulic parameters of the soil, possibly due to irrigation and good rainfall distribution in the area. Furthermore, the variability in US simulations were higher for GCTB than in Bare treatment, suggesting that the GCTB has a larger influence in SAMUCA’s variability than for the hydraulic parameters in the conditions of this study. The UG and UGS had the same capacity to quantify the variability present in the environment for the treatments Bare and GCTB. In this case, sensitivity to soil parameters can simply be ignored and genotype parameters can be chosen as the only source of variability for practical applications. Our suggestion for future work is to explore environments without irrigation, different amounts of GCTB and other soil parameters present in the model.

Corrective and maintenance phosphorus fertilization on sugarcane yield in Oxisols

Abstract The objective of this work was to evaluate sugarcane (Saccharum spp.) yield in response to corrective and maintenance phosphorus fertilization in Oxisols. Two experiments were carried out in randomized complete blocks with four replicates. In the corrective fertilization treatments, 150 kg ha-1 P2O5 were broadcast and incorporated before planting. In the maintenance fertilization treatments, 40 kg ha-1 P2O5 per year were applied over the trash blanket. All treatments, except the control, were fertilized with 170 kg ha-1 P2O5 in the planting furrow. The first experiment was carried out in a sugarcane expansion area and the second, in a replanting area, in Oxisols with a low and high phosphorus availability, respectively. In the first experiment, corrective fertilization increased cane yield in 13.4 Mg ha-1 for plant cane and in 14.6 Mg ha-1 for the average of four ratoon crops, whereas maintenance fertilization increased yield in 17.7 and 8.1 Mg ha-1 for the average of four ratoon crops for the treatments without and with corrective fertilization, respectively. In the second experiment, there were no significant differences between treatments regarding yield. Corrective and maintenance phosphorus fertilization should be considered for sugarcane in areas where soil phosphorus availability is limiting.

Sugarcane straw preservation results in limited immobilization and improves crop N-fertilizer recovery

Current knowledge indicates that sugarcane straw is a short-term sink of fertilizer nitrogen (N) due to N immobilization during the decomposition process. This study aimed to determine whether sugarcane straw removal from the field benefits the N-fertilizer recovery by plant (NRP), and if legume cultivation will further improve NRP. Half of a field was planted with sunn hemp (Crotalaria spectabilis) and half was left fallow. In the second ratoon, treatments with 0, 50, and 100% of sugarcane straw maintenance levels were installed, receiving 120 kg ha−1 N over straw. A microplot of ammonium nitrate labeled with 1.99% atoms 15N was included. NRP was quantified at 92, 164, and 264 days after fertilization (DAF). At harvest (264 DAF), soil samples and straw (<4 mm and >4 mm fractions) were collected to determine N-fertilizer recovery in the soil (NRS) and in the straw (NRSt). Maintaining 50 and 100% of straw improved NRP over the sugarcane cycle. NRP was not improved by crop rotation cultivation and NRS averaged 50% in the entire soil profile. NRSt at harvest averaged 1–3% in the 50% and 100% straw levels. Contrary to the current view, N-fertilizer immobilization in the straw was negligible and keeping straw could improve NRP. The findings indicate that increasing N rates in green cane trash blanket system to compensate for the N-fertilizer immobilization is not necessary, and that straw removal for bioenergy production will change the short-term demand for N-fertilizer.

Short Communication: Investigating environmental impacts of long-term monoculture of sugarcane farming in Indonesia through DPSIR framework

Abstract. Putra RP, Ranomahera MRR, Rizaludin MS, Supriyanto R, Dewi VAK. 2020. Short Communication: Investigating the environmental impacts of long-term monoculture of sugarcane farming in Indonesia through DPSIR framework. Biodiversitas 21: 4945-4958. An increasing trend of sugar demand in Indonesia due to the rising population has forced the government to boost its national sugarcane production through intensification program. Long-term monoculture system has long been practiced by sugarcane growers in Indonesia, particularly by large sugar companies for more than 30 years. This farming method bolsters the government’s program in scaling-up national sugar production. Through a literature study, the present study analyzed the impacts of long-term sugarcane monoculture in Indonesia on agroecosystem functions by using the Driver-Pressure-State-Impact-Response (DPSIR) framework. Results showed that long-term sugarcane monoculture leads to decreased soil quality, lowered hydrological functions, reduced agrobiodiversity, and increased greenhouse gas emissions. Those conditions corresponded to reduced sugarcane yield and productivity, increased pests and diseases, decreased income gained by growers, higher dependencies on chemicals, and higher cultivation costs. In the end, we proposed several sustainable crop management to mitigate the detrimental effects of sugarcane monoculture practice in Indonesia. These include performing crop break or rotation with legume or the other cash crop, intercropping, green harvesting and trash blanket, precision agriculture methods, and soil amendment with organic matters. However, some constraints in implementing those sustainable crop management, such as inadequate knowledge and capital, should be considered. The information given in this study can be used by sugarcane growers or companies, policymakers, and sugarcane-related stakeholders as considerations to improve sugarcane productivity while at the same time minimizing its impact on the environment.

Effect of crop residue management on damage by Diatraea saccharalis (Lepidoptera: Crambidae), its egg parasitoids and the ants associated with sugarcane.

In the American continent, the sugarcane borer Diatraea saccharalis (F.) is the main pest in sugarcane producing areas. The objective of this study was to assess the effect of crop residue management on damage by D. saccharalis, its egg parasitoids and the ants associated with sugarcane. The study was carried out during 2011-2012, 2012-2013 and 2013-2014 crop cycles, in three commercial fields located in different regions of Tucumán state, Argentina. Two types of crop residue management (= treatments) were compared: conservation of trash at the soil surface (CT) and trash burning (TB). In 'trash conservation' treatment, crop residue was allowed to remain over the soil surface during the whole sugarcane growing season, while the second treatment consisted of complete burning of trash blanket approximately 2 weeks after harvest. The injury level was measured by recording the number of stalks bored and internodes bored. Parasitism was estimated by counting the total number of eggs and number of black eggs (which indicates the occurrence of egg parasitoids). Ants (Formicidae) richness was calculated by two estimators; abundance-based coverage estimator and incidence-based coverage estimator, using the non-parametric richness estimators: Chao 2 and Jackknife. Finally, the indicator value was estimated through the measurement of specificity and fidelity. In all the parameters studied no significant difference was found between TB and CT treatments.

Modelling the trash blanket effect on sugarcane growth and water use

The traditional practice of burning at the pre-harvesting of sugarcane has being phased-out in Brazil, resulting in the maintenance of a crop s residue layer on soil surface, namely the Green Cane Trash Blanket (GCTB). New technologies for electricity and second-generation ethanol (2G) production from crop residues have raised the question on what would be the optimum amount of crop residue left on the field to keep the agronomic and environmental benefits of GCTB. To support informed decision making on sugarcane trash management, we updated, evaluated and applied a new version of the SAMUCA model to simulate the sugarcane growth and water use under the GCTB effect. The updated model was calibrated and parameterized for bare soil and GCTB conditions and evaluated across different Brazilian regions. Thirty-year simulations were then conducted with the updated model to quantify the effects of GCTB on sugarcane growth and water use where sugarcane is traditionally grown in Brazil. The updated version of SAMUCA model showed equal or superior performance when compared with widely-used process-based models for sugarcane. Based on our 30-year simulations, the GCTB exhibited a high probability to promote a beneficial effect on sugarcane yields in dry climates (>90%), with the potential for increasing, on average, 14 ton ha−1 of fresh cane yield in Petrolina, Brazil. Although the beneficial effect on yields were not significant in humid regions, the maintenance of 12 ton ha−1 of GCTB was associated with a high probability (>87%) in reducing the water use of sugarcane cropping system by 89 mm, on average, potentially reducing irrigation demand in the early stages of crop development while protecting crop production under dry spell events. The new version of SAMUCA model offers as a tool for decision making on mulch management in sugarcane plantations.

Effects of a mulch layer on the assemblage and abundance of mesostigmatan mites and other arthropods in the soil of a sugarcane agro-ecosystem in Australia

Sugarcane farmers can utilise a soil conservation technique called green cane trash blanketing, a form of mulching that can increase plant productivity through a number of channels, e.g., via altering soil physical, chemical and biological characteristics, and influence soil arthropod assemblages. Predatory mites (Mesostigmata) are important components of soil communities because they can control populations of other soil-dwelling pest species. Our aim was to characterise mulch-influenced predatory Mesostigmata community assemblages in sugarcane soils in Queensland, Australia. We found that application of a mulch layer significantly increased the abundance of Mesostigmata, and oribatid mites and collembolans, in soils. Furthermore, we observed that the assemblages of Mesostigmata in soil covered by mulch were significantly different to those in bare soil; and the assemblages of Mesostigmata changed over time. The assemblages of Mesostigmata, but not Oribatida or collembolans, were significantly different in soil under mulch depending on whether the mulch was freshly laid, or decomposing. Our results show that the use of mulch, specifically the green cane trash blanket, can increase overall microarthropod abundance including Mesostigmata. This is likely due to increased habitat complexity and changing resource availability.

Liming improves soil microbial growth, but trash blanket placement increases labile carbon and nitrogen availability in a sugarcane soil of subtropical Australia

Liming has been widely used to decrease soil acidity, but its effects on soil nitrogen (N) availability and microbial processes in sugarcane fields are largely unknown. Adjacent sugarcane soils at 26 months after liming (26ML), 14 months after liming (14ML) and with no lime amendment (CK) in Bundaberg, Australia, were selected to investigate the effect of liming on soil N bioavailability and microbial activity in a long-term subtropical sugarcane cropping system. Liming in both 14ML and 26ML treatments significantly increased soil pH (by 1.2–1.4 units) and exchangeable Ca2+ (&gt;2-fold) compared with the CK treatment. The lower concentrations of hot water extractable organic carbon (C) and total N and ammonium-N in the 14ML, compared with the CK and 26ML treatments, can be attributed to the absence of trash blanket placement in the former. Enhanced microbial immobilisation due to improved soil pH by liming (14ML and 26ML treatments) led to increased soil microbial biomass C and N, particularly in the presence of a trash blanket (26 ML treatment), but decreased soil respiration and metabolic quotient indicated that acidic stress conditions were alleviated in the liming treatments. Soil pH was the main factor governing soil enzyme activities, with an overall decrease in all enzyme activities in response to liming. Overall, liming and trash blanket practices improved sugarcane soil fertility. Further study is warranted to investigate the shifts in soil microbial community composition and the diversity and abundance of N-associated functional genes in response to liming in sugarcane fields.

Optimizing urease inhibitor usage to reduce ammonia emission following urea application over crop residues

Abstract Nitrogen loss as ammonia (NH3) is a major problem when urea is topdressed over crop residues. The treatment of urea with N-(n-butyl) thiophosphoric triamide (NBPT) temporarily inhibits urease activity and reduces NH3 volatilization loss under many agro­ecological conditions. However, the amount of straw on the soil in green sugarcane trash blanketing (GCTB) systems affects the success of NBPT in reducing NH3 loss. We hypothesized that an increase in the NBPT concentration in urea above the current level (530 mg NBPT kg−1 urea) in Brazil is necessary to reduce the NH3 volatilization and to improve the efficiency of urea in GCTB systems. We evaluated the NH3 loss from urea treated with NBPT under field conditions in GCTB systems. Six field trials were conducted across the State of Sao Paulo, the main sugarcane-growing region in Brazil. The treatments were urea, ammonium nitrate, urea treated with NBPT at concentrations of 530, 850, 1500, and 2000 mg kg−1, and a control plot without N fertilizer. The amount of volatized NH3 was assessed through a closed semi-static collector containing two acid-trap foam disks, and analyzed by colorimetry using flow injection analysis. NBPT concentrations above 530 mg kg−1 delayed the time of maximum rate of loss and also reduced cumulative NH3 loss. Ammonia emissions were linearly reduced with increasing NBPT concentrations until 1000 mg kg−1. Any further increase in the NBPT concentration did not result in a substantial reduction of NH3 volatilization. Increasing the NBPT concentration in urea is an effective approach to optimize the adoption of urea-based fertilizers in tropical GCTB systems.

Long Term Sugarcane Crop Residue Retention Offers Limited Potential to Reduce Nitrogen Fertilizer Rates in Australian Wet Tropical Environments.

The warming of world climate systems is driving interest in the mitigation of greenhouse gas (GHG) emissions. In the agricultural sector, practices that mitigate GHG emissions include those that (1) reduce emissions [e.g., those that reduce nitrous oxide (N2O) emissions by avoiding excess nitrogen (N) fertilizer application], and (2) increase soil organic carbon (SOC) stocks (e.g., by retaining instead of burning crop residues). Sugarcane is a globally important crop that can have substantial inputs of N fertilizer and which produces large amounts of crop residues (‘trash’). Management of N fertilizer and trash affects soil carbon and nitrogen cycling, and hence GHG emissions. Trash has historically been burned at harvest, but increasingly is being retained on the soil surface as a ‘trash blanket’ in many countries. The potential for trash retention to alter N fertilizer requirements and sequester SOC was investigated in this study. The APSIM model was calibrated with data from field and laboratory studies of trash decomposition in the wet tropics of northern Australia. APSIM was then validated against four independent data sets, before simulating location × soil × fertilizer × trash management scenarios. Soil carbon increased in trash blanketed soils relative to SOC in soils with burnt trash. However, further increases in SOC for the study region may be limited because the SOC in trash blanketed soils could be approaching equilibrium; future GHG mitigation efforts in this region should therefore focus on N fertilizer management. Simulated N fertilizer rates were able to be reduced from conventional rates regardless of trash management, because of low yield potential in the wet tropics. For crops subjected to continuous trash blanketing, there was substantial immobilization of N in decomposing trash so conventional N fertilizer rates were required for up to 24 years after trash blanketing commenced. After this period, there was potential to reduce N fertilizer rates for crops when trash was retained (≤20 kg N ha–1 per plant or ratoon crop) while maintaining ≥95% of maximum yields. While these savings in N fertilizer use were modest at the field scale, they were potentially important when aggregated at the regional level.

Best Practices of Nitrogen Fertilization Management for Sugarcane Under Green Cane Trash Blanket in Brazil

The low efficiency of nitrogen (N) use from fertilizer applied to sugarcane is a major concern worldwide threatening the sustainability of sugarcane production. Further, the significance of N losses to the environment is becoming more important as global warming becomes a more significant issue. Improving nitrogen use efficiency is a major challenge for sugarcane cropping systems worldwide. Amongst other factors, N application method has a significant effect on the efficiency with which N is used by the crop. In Brazil, the sugar industry is rapidly moving towards green cane harvesting and the maintenance of a trash blanket (GCTB) between crops in a cycle. However, there is limited information regarding the most appropriate nitrogen fertilizer placement between ratoon crops in a GCTB system. The aim of this research was to evaluate the effect of different nitrogen application methods on the productivity of ratoon sugarcane being grown under a green cane trash blanket (GCTB) system. The application methods tested were: (1) control (no fertilizer applied), (2) fertilizer incorporated at 0.2 m in the centre of each interrow, (3) fertilizer applied to the GCTB surface in both sides of the row, and (4) fertilizer incorporated at 0.08 m depth in both sides of the row. The incorporation of the fertilizer at 0.08 m depth on both sides of the row resulted in the best agronomic performance, producing approximately 13 and 12 % more cane tonnage and sugar yield, respectively, when compared to band surface application, which was the second best method.

Impacts of Crop Residue on Damage by Sugarcane Pests During the Tillering Phase in Argentina

One of the most important recent changes in sugarcane cultural practices in Tucuman, Argentina, is the adoption of the practice of green-cane harvesting, which involves harvesting the sugarcane crop in the absence of burning. The objective of this study was to assess the impact of the postharvest crop residue (also sometimes known as “trash blanket”) on Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) and Pseudaletia uni puncta Haworth (Lepidoptera: Noctuidae) population dynamics in sugarcane. The study was conducted in ratoon crops for 3 growing seasons (2011, 2012, and 2013) and at 3 locations in the state of Tucuman, Argentina. The treatments consisted of rows with the crop residue burned and the crop residue retained. Removal of the crop residue by burning, compared with retention, resulted in significantly greater crop damage by E. lignosellus in all locations and years. In contrast, damage by P. unipuncta was observed exclusively on plots where crop residue was retained. Comparing the pest status of 2 insects, E. lignosellus seems to be more consistently deleterious to sugarcane yield than P. unipuncta, and chemical control of this species is not very effective. Therefore, leaving the crop residue in place seems to be the most appropriate crop management approach, although it is important also to monitor P. unipuncta populations in order to implement control should it be necessary.

The Practice of Green Cane Trash Blanketing in the Irrigated Zone of Mauritius: Effects on Soil Moisture and Water Use Efficiency of Sugarcane

Sugarcane growers in Mauritius are using mechanized harvesting to reduce costs. This practice results in a trash blanket which contributes to conserve soil moisture, but potential savings in irrigation water have yet to be quantified. An on-farm study was undertaken at three sites in the irrigated coastal zone of Mauritius under sub-humid to humid mega-thermal climate and soils that were oxisol or inceptisol. Trials were conducted in ratoon crops under centre pivot irrigation and treatments with or without trash blanket, as well as different irrigation regimes. Sensors were used to log soil moisture data at 20, 40 and 60 cm depths. Increased drainage was observed under trash blanket during rainfall events and cumulative drainage for a 4-month wet period amounted to 43 and 240 mm for no-trash and trash blanket treatments respectively. Daily crop water use was higher with trash blanket, consumption being 4.9 and 5.1 mm day−1 compared to 4.2 and 4.6 mm day−1 for no-trash during peak growth at Savannah and Medine. Sugarcane yield was higher by 7.2 and 6.6 t ha−1 year−1 with trash blanket compared to no-trash, whereas water use efficiency increased by 8 and 9 kg ha−1 mm−1. At Saint Antoine, trash blanket increased the yield difference between irrigated and rainfed crops by 8.6 t ha−1 and improved water use efficiency by 7 kg ha−1 mm−1 when irrigated. Seasonal water equivalence of the trash blanket amounted to 62, 54 and 72 mm water at Savannah, Medine and Saint Antoine, a potential saving of 10–15 % in irrigation water.

THE RESPONSE OF SUGARCANE TO TRASH RETENTION AND NITROGEN IN THE BRAZILIAN COASTAL TABLELANDS: A SIMULATION STUDY

SUMMARYTo evaluate the impact of trash management on sugarcane production and N fertiliser requirements in environmental conditions of Brazilian coastal tablelands, a simulation was conducted with APSIM-Sugar cropping systems model. The model was parameterised for, and validated against results from a long term (over 23 years) experiment comparing the system-burnt trash and green cane trash blanketing (GCTB), in Linhares-ES. Simulations were conducted over two crop cycles (14 years) with different management (100%, 75%, 50%, 25% GCTB and burnt trash), and N fertiliser rates from 0 to 240 kg ha−1 (in 40 kg ha−1 increments) on the ratoon crops, and 75% of these rates on the plant crops. Measured cane yields and soil carbon were simulated well by the model. The RMSE (root mean square error) of predictions in burnt and GCTB treatments were 14.02 Mg ha−1 and 13.45 Mg ha−1 for yield, and 0.09 and 0.13% for soil carbon. In the simulation, the cane yield responded positively to the GCTB systems. Optimum N rates were higher in the 100%, 75% and 50% GCTB than with burnt trash and 25% GCTB reflecting the greater yields under GCTB systems. The response to trash retention was dependent on N fertiliser, and it was smaller or even negative at lower N rates. With adequate N, the positive responses were predicted to occur in all crops after the imposition of GCTB system. The removal of any proportion of the trash reduced the potential sugarcane yield. The simulations showed that average environmental losses of N are likely to be greater from trash-retained systems at all N fertiliser rates.

Simulating Long-Term Effects of Trash Management on Sugarcane Yield for Brazilian Cropping Systems

Historically, trash has been burnt in Brazil. Recently, increasingly crops are being harvested green with trash retailed as blanket (GCTB) due to environmental restrictions, and because of the trash use as a feedstock for bioenergy. The presence of a trash blanket affects sugarcane crops, by conservation of soil moisture and a potential to increase soil carbon (C) and nitrogen (N). To gain insights into the impacts of the burnt-to-green cane trash blanket transition, a simulation study was conducted with the APSIM-Sugar crop model. Simulations were conducted over 100 years for 3 locations: Piracicaba-SP, Palmas-TO, and Maceio-AL, addressing 2 research questions: (1) what is the yield impact of the transition from burnt to GCTB due to soil N, C and water changes; and (2) what is the impact of trash removal on yield in fields managed under GCTBs. Both questions were answered based on the same set of simulations. We simulated the transition to GCTB after 25 years of burnt management combining four N rates and 3 trash removal treatments [no trash removal, 50 % trash removal (50 %) and 90 % trash removal (90 %)]. Simulated sugarcane yields have potential to respond positively to trash retention, and stalk yield for 50 and 90 % treatments decreased at rates proportional to the trash removal rates for Maceio and Piracicaba. In Palmas, located in a drier region, simulations showed trash retention having a positive effect firstly due to soil water retention. In Piracicaba, simulations also illustrated the potential negative, short-term impact of trash blanketing on yields due to the N immobilization by the decomposing trash.

Effects of residue management on nitrogen losses in surface and sub-surface water from sugarcane fields

The effect of three sugarcane (Saccharum officinarum L.) residue-management plans on nitrogen losses in surface runoff and sub-surface leachate was studied for 3 years. The three management plans evaluated were conventional burning (CB), compost application with burning (COMB), and remaining green cane trash blanketing (GCTB) treatment. In the CB treatment, sugarcane residue was burned after harvest. The COMB treatment consisted of compost applied at ‘off bar’ with sugarcane residue burned immediately after harvest. Compost was applied in the amount of 13.4 Mg ha−1 annually. Surface runoff was collected with automatic refrigerated samplers and sub-surface leachate was collected with pan lysimeters over a period of 3 years. Total nitrogen (TN), NO3/NO2–N, and NH4–N were measured. The mean losses of nitrogen (TN, NO3/NO2–N, and NH4–N) from the COMB treatment after the burning procedure (post-harvest, years 2 and 3) were on average 2.7 times higher than those before harvest and burning (pre-harvest, year 1). Mean leaching losses of NO3/NO2–N were 0.36, 0.82, and 0.10 kg ha−1 for the CB, COMB, and GCTB treatment, respectively. The losses of NO3/NO2–N from the GCTB treatment in surface runoff and sub-surface leachate were significantly reduced compared to the CB and COMB treatment.

Long-term decomposition of sugarcane harvest residues in Sao Paulo state, Brazil

Abstract Crop residues returned to the soil are important to preserve fertility and sustainability. This research addressed the long-term decomposition of sugarcane post-harvest residues (trash) under reduced tillage, therefore field renewal was performed with herbicide followed by subsoiling and ratoons were deprived of interrow scarification. The trial was conducted in the northern Sao Paulo State, Brazil during four consecutive crops (2005–2008) where litter bags containing 15 N-labeled trash were disposed in the field attempting to simulate two distinct situations: the previous crop trash (PCT) or residues incorporated in the field after tillage, and post-harvest trash (PHT) or the remains of plant-cane harvest. Decomposition rates regarding dry matter (DM), carbon (C), root growth, plant nutrients (N, P, K, Ca, Mg and S), lignin (LIG) cellulose (CEL) and hemicellulose (HCEL) contents were assessed for PCT (2005 ndash;2008) and for PHT (2006–2008). There were significant reductions on DM and C:N ratio due to C losses and root growth within the litter bags over time. The DM from PCT and PHT decreased 96% and 73% after four and three crops, respectively, and the higher nutrients release were found for K, Ca and N. The LIG, CEL and HCEL concentrations in PCT decreased 60%, 29%, 70% after four crops and 47%, 35%, 70% from PHT after three crops, respectively. Trash decomposition was driven mainly by residues biochemical composition, root growth within the trash blanket and the climatic conditions during the crop cycles.