Effects Of Straw Removal Research Articles

Straw removal reduces Cd availability and rice Cd accumulation in Cd-contaminated paddy soil: Cd fraction, soil microorganism structure and porewater DOC and Cd

The impacts of straw removal on rice Cd absorption, behaviour of Cd and microbial community in rhizosphere soil were investigated in paddy fields over two consecutive seasons. The results of the experiments in two fields revealed that straw removal promoted the transformation of soil Cd from acid-extractable and oxidisable fraction to residual fraction and reduced soil DTPA-Cd content with the reduction in DOC and Cd ions in soil porewater, thereby decreasing Cd content in rice. Specifically, the Cd content in brown rice was below 0.2 mg·kg−1 when all rice straw and roots were removed in the slightly Cd-contaminated soils. The α-diversity of soil microbial communities was less influenced by continuous straw removal, β-diversity was altered and the relative abundances of Anaeromyxobacter, Methylocystis and Mycobacterium microbes were increased. Redundancy analysis and network analysis exhibited that soil pH predominantly influenced the microbial community. Path analysis revealed that the Cd content in brown rice could be directly influenced by the soil Total-Cd and DTPA-Cd, as well as soil pH and OM. Straw removal, including roots removal, is an economical and effective technique to reduce Cd accumulation in rice plants.

Linking soil physical quality to shoot and root biomass production in scenarios of sugarcane straw removal

Understanding how sugarcane straw removal affects soil physical attributes and root development over successive cultivation years is critical for sustainable straw-based bioenergy production. The aim of this study was to evaluate the effects of straw removal on soil physical quality and its relationship with sugarcane root development and crop yield in soils with contrasting textures. Three straw removal rates corresponding to total removal (TR), moderate removal (MR), and no removal (NR) were arranged in a randomized block design with four replicates. Soil was sampled at depths of 0–0.10, 0.10–0.20, and 0.20–0.40 m to determine soil bulk density, macro- and microporosity, soil penetration resistance, and carbon stock. Annual assessments of sugarcane root and stalk dry biomass were conducted. Overall, excessive straw removal rates were detrimental to soil porosity, C stock, and increased bulk density in the surface layer over successive years compared to moderate and no removal rates. Higher soil penetration resistance levels were observed under total removal, reaching values of 2.6 MPa in the 0–0.10 m layer in both soils. Average reductions in root biomass of 23–33% were verified at moderate and total removal rates in both soils, which affected sugarcane stalk yield, with maximum losses of 24% over crop cycles in the clayey soil. In the sandy loam soil, increases in soil C were correlated with reduced soil penetration resistance, which positively influenced root biomass production. Soil compaction over the years was particularly detrimental in the clayey soil, where the biomass production performance of sugarcane roots and stalk yield decreased in response to increased soil bulk density. Our results suggest that reductions in root biomass may occur in response to straw removal, as well as the loss of soil physical quality induced by soil compaction, with negative effects on C accumulation and soil resistance to root penetration.

An integrated analysis of transcriptome and metabolome provides insights into the responses of maize (Zea mays L.) roots to different straw and fertilizer conditions

Returning straw back to the field with an appropriate amount of fertilizer has been proven to be beneficial in the promotion of soil fertility, crop yield, and the sustainability of an agricultural system. However, little is known regarding the molecular and metabolic understandings of enhanced crop growth in a straw return system. By performing an integrated transcriptomic and metabolomics analysis, we investigated the effects of straw removal and straw return with two chemical fertilizer rates on root morphology in a mesh bag field experiment on maize in northwest China. Our results showed that straw return played a role in root thickening (bigger root diameter), while fertilization enhanced root branching (more root number). Different from straw return alone, straw return with fertilizer significantly decreased the root/shoot ratio ( p < 0.01) and increased the total root number ( p < 0.01), and root total nitrogen concentration ( p < 0.001). Root morphological responses were tightly associated with transcriptional regulation (e.g., root dry weight, Mantel’s r = 0.6468, p < 0.001) and metabolism modulation (e.g., root/shoot ratio, Mantel’s r = 0.7229, p < 0.001), mainly including the activation of genes related to phenylpropanoid and flavonoid metabolic pathways (e.g. , BGLU , PAL and POD ), the fine regulation of genes associated with auxin synthesis, homeostasis, flow and signaling (e.g., YUC , AUX1 and SAUR ), and cell wall remodeling (e.g., CESA and EXPA ), and the regulation of transcription factors and genes that function in the development of roots (primary, seminal, and lateral), root hairs, root tips, and root caps (e.g., BBM , LRP1 and RTCS ), and the accumulation of different metabolites (e.g., indole, esculin, and sucrose) under straw return with fertilization. We revealed important insights into the growth-promoting and morphology-modifying effects of straw return, as well as its highly novel effects on the transcriptional regulation and metabolism reprogram of maize root, which may help to elucidate how maize roots respond under straw return conditions to optimize soil resource acquisition and then guide the suitable utilization of crop residue resources in the agricultural system. • Straw played different roles from fertilizer in maize roots morphological modification. • Root growth response to straw was tightly associated with transcriptional regulation. • Genes related to IAA synthesis, homeostasis, flow and signaling were fine-regulated. • R/T ratio showed the strongest Mantel’s correlate with metabolism modulation. • Mechanism governing the enhanced maize growth in a straw-return system was revealed.

Effects of long-term straw return on soil organic carbon fractions and enzyme activities in a double-cropped rice paddy in South China

Long-term straw return is an important carbon source for improving soil organic carbon (SOC) stocks in croplands, and straw removal through burning is also a common practice in open fields in South China. However, the specific effects of long-term rice straw management on SOC fractions, the related enzyme activities and their relationships, and whether these effects differ between crop growing seasons remain unknown. Three treatments with equal nitrogen, phosphorus, and potassium nutrient inputs, including straw/ash and chemical nutrients, were established to compare the effects of straw removal (CK), straw return (SR), and straw burned return (SBR). Compared to CK, long-term SR tended to improve the yield of early season rice (P=0.057), and significantly increased total organic carbon (TOC) and microbial biomass carbon (MBC) in double-cropped rice paddies. While SBR had no effect on TOC, it decreased light fraction organic carbon (LFOC) in early rice and easily oxidizable organic carbon (EOC) in late rice, significantly increased dissolved organic carbon (DOC), and significantly decreased soil pH. These results showed that MBC was the most sensitive indicator for assessing changes of SOC in the double-cropped rice system due to long-term straw return. In addition, the different effects on SOC fraction sizes between SR and SBR were attributed to the divergent trends in most of the soil enzyme activities in the early and late rice that mainly altered DOC, while DOC was positively affected by β-xylosidase in both early and late rice. We concluded that straw return was superior to straw burned return for improving SOC fractions, but the negative effects on soil enzyme activities in late rice require further research.

Soil dissolved organic carbon responses to sugarcane straw removal

AbstractGlobal demand for bioenergy increases interest in biomass‐derived fuels, as ethanol from sugarcane straw. However, straw is the main carbon source to soil and its removal reduces C input, affecting active fractions (dissolved organic carbon, DOC) and C storage. To quantify the effects of straw removal on DOC and C stocks, we built lysimeter system using soil (Rhodic Kandiudox) from sugarcane field. We evaluated four soil depths (1, 20, 50 and 100 cm) and four straw removal rates: no removal NR, medium MR, high HR and total TR, leaving 12, 6, 3 and 0 Mg/ha on the soil surface, respectively. After rainfall, drainage water was collected and analysed for DOC content. Soil C stocks were determined after the 17‐month. Total DOC released at 1‐cm depth amounted to 606, 500, 441 and 157 kg/ha in NR, MR, HR and TR, respectively. Net‐DOC suggests straw as the main source of DOC. Most of DOC in NR (50%) was retained within the 1–20 cm layer, resulting in higher C stock (10 Mg/ha) in the topsoil. In HR and MR, DOC retention was higher within 20–50 cm, suggesting differences in DOC composition. DOC in TR was 40% higher at 20 cm than at 1 cm, indicating C losses from topsoil. Low concentrations of DOC were found at 100‐cm depth, but representing 30% in TR. Straw removal for bioenergy production is sustainable, but we should leave at least 3 Mg/ha of straw to ensure DOC production and soil C storage, taking account the DOC contribution to key soil functions.

Pine Straw Raking and Growth of Southern Pine: Review and Recommendations

Pine straw, the uppermost forest floor layer of undecayed, reddish-brown pine needles, is raked, baled, and sold as a landscaping mulch throughout the southeastern United States. Loblolly (Pinus taeda, L.), longleaf (P. palustris, Mill.), and slash (P. elliottii Engelm. var. elliottii) pine are the three southern pine species commonly raked for pine straw. The value of pine straw as a forest product is large. Private landowner pine straw revenues have steadily increased throughout the southeastern United States over the past two decades and now total more than USD 200 million. Information is limited on the short- or long-term effects of pine straw removal on foliage production or stand growth in southern pine stands. Results from most published studies suggest that annual pine straw raking without fertilization on non-old-field sites reduces straw yields compared to no raking. Old-field sites often do not benefit from fertilization with increased pine straw or wood volume yields. Though fertilization may be beneficial for pine straw production on some sites, understory vegetation presence and disease prevalence may increase following fertilization. This review addresses pine straw removal effects on pine straw production and stand growth parameters based on recent studies and provides fertilization recommendations to maintain or improve pine straw production and stand growth and yield.

Straw Removal Effects on Sugarcane Root System and Stalk Yield

The sugarcane (Saccharum spp. L.) mechanical harvesting system leaves a large amount of straw mulch on the soil surface. The straw mulch may affect soil conditions, root regrowth, and sugarcane yield. Thus, this study assessed the response of sugarcane root system growth and stalk yield to different rates of straw removal. An experiment was conducted in a Rhodic Kandiudox with sand clay loam texture to test the impact of four rates of straw removal: no removal (18.9 Mg ha−1 of dry mass); moderate removal (8.7 Mg ha−1); high removal (4.2 Mg ha−1) and total removal on sugarcane root system and stalk yield. Higher concentrations of roots (60%) were found in the first 40 cm of soil. Moderate straw removal resulted in higher root mass (3.6 Mg ha−1) and stalk production (23 Mg ha−1 of dry mass). However, no straw removal reduced root mass by &lt;40% (2099 kg ha−1) and reduced stalk yield by &gt;20% (105 Mg ha−1). Through regression analysis, it was estimated that retaining between 8.5 and 13 Mg ha−1 of straw resulted in the highest root mass and stalk yield. Managing straw removal to retain a moderate amount enables producers to sustain suitable soil conditions for sugarcane root growth and stalk production while providing straw for industrial use.

Soil Macrofauna Responses to Sugarcane Straw Removal for Bioenergy Production

Sugarcane (Saccharum officinarum) residue (straw) has been identified as a promising feedstock for bioenergy production, but excessive straw removal may impair soil macrofauna and related ecosystem services. To quantify straw removal effects on abundance, richness, and diversity of soil macrofauna, four experiments were conducted in Sao Paulo state, Brazil, under different edaphoclimatic conditions. A secondary goal was to evaluate seasonal changes on soil macrofauna and identify linkages between those changes and soil chemical and physical attributes. Four straw removal treatments (NR, no removal, LR, low removal, HR, high removal, and TR, total removal) were evaluated. Macrofauna and other soil attributes were sampled within the 0- to 0.30-m depth increment. Soil macrofauna were impaired by TR with the magnitude of response being related to both edaphoclimatic conditions and management practices. Numerous interactions among seasons, straw removal rates, and soil macrofauna were found, especially for total abundance and diversity of organisms. Partial straw removal (HR and LR) may be a strategy to protect soil health and increase bioenergy production with minimal effects on soil macrofauna, although long-term experiments are needed to confirm our hypothesis. The NR treatment generally had better soil quality as indicated by greater soil moisture, macropore number, soil organic carbon (SOC) content, and soil fertility, which led to a higher abundance of most macrofauna organisms. Total removal resulted in greater soil compaction and decreased macrofauna abundance, especially in clay soils. Our findings confirm that an integrated approach using soil indicators as guidelines should be adopted to better predict sustainable straw management practices for sugarcane in Brazil.

Multilocation Straw Removal Effects on Sugarcane Yield in South-Central Brazil

Sugarcane straw is a crop residue that has a dual purpose and can be maintained on the fields or used to produce bioenergy. The straw retention in the field provides multiple ecosystem services, and the complex interactions between straw and yield responses are hard to predict by local studies. The aim of this study was to investigate the straw removal effects on sugarcane yield in south-central Brazil. To achieve the objective, a set of 21 field studies was conducted in contrasting edaphoclimatic conditions. In addition, data of seven studies from the literature were included to build a more robust dataset. Since straw removal treatments were not homogeneous in all experiments, they were grouped as follows: NR, no removal (baseline treatment); LR, low removal; MR, moderate removal; and TR, total removal. To facilitate the data analysis, the experiments were gathered in four macroregions: southern Goiás, western São Paulo, central-eastern São Paulo, and northeastern São Paulo. The site location was the most effective individual factor to explain the straw removal effects on sugarcane yields. Compared with NR treatment, the average yield losses induced by LR, MR, and TR were 2, 10, and 13 Mg ha−1 in southern Goiás and 2, 4, and 6 Mg ha−1 in western São Paulo states, respectively. In other regions, no clear pattern was observed, and only site-specific effects were observed. Straw removal affected sugarcane yields in all soil types, but higher responses were observed under best conditions for sugarcane growth (i.e., clayey soils in southern Goiás). Our findings indicated harvesting season has a relevant role on determining yield responses to straw removal and younger ratoons are more responsive to straw removal. Conclusions from this study suggest straw removal recommendations cannot be designed based on isolated factors but require holistic and integrated knowledge to ensure that the straw amount left on field is enough to sustain multiple soil ecosystem services and crop yields.

Straw Removal Affects Soil Physical Quality and Sugarcane Yield in Brazil

Industrial use of sugarcane straw for bioenergy production represents a promising opportunity for the Brazilian sugarcane sector. Nonetheless, intensified straw removal may aggravate the effects of mechanized harvesting and increase the risks of soil compaction, declining sugarcane yield. An experiment was designed, and four field studies were conducted to evaluate the cumulative effects of straw removal on soil physical attributes (bulk density, BD; soil resistance to penetration, SRP; macroporosity, MaP; microporosity, MiP, and mean weight diameter of soil aggregates, MWD) and their relationship with crop yield under clayey and sandy soils in the Sao Paulo state, Brazil. In each field study, four straw removal rates (no removal, NR; low removal, LR, removal of 5 Mg ha−1; high removal, HR, removal of 10 Mg ha−1; and total removal, TR, removal of 15 Mg ha−1) were arranged in a randomized block design with four replicates. The 4-year intensive management of straw removal (HR and TR) resulted in an increased soil compaction (BD and SRP values) and reduced the MWD in both sandy and clayey soils. Our findings also showed that these effects are more significant in sandy soils, where soil carbon content was substantially reduced in HR and TR treatments. Sites with higher BD and SRP induced by straw removal were strongly associated with lower sugarcane yields, especially in sandy soils. Conversely, our findings indicate that LR was not detrimental to soil physical quality and sugarcane yield. Nevertheless, considering the multifunctionality of straw in sustaining multiple ecosystem services in different soil types, straw management should be defined taking into consideration site-specific conditions. We advocate that recommendations for straw removal should also be combined with other conservationist soil management practices in order to minimize soil compaction and its negative implications on sugarcane yield and other ecosystem services.

Straw Removal Effects on Soil Water Dynamics, Soil Temperature, and Sugarcane Yield in South-Central Brazil

The use of sugarcane straw as bioenergy feedstock has been encouraged in recent years due to its potential to mitigate greenhouse gases emissions. Nevertheless, the indiscriminate straw removal causes soil damages, impairing crop development and productivity. Experiments in three sugarcane growing locations (Quata-SP, Chapadao do Ceu-GO, and Quirinopolis-GO) were conducted over 2 years to evaluate soil water dynamics, soil temperature, and sugarcane yield under diverse edaphoclimatic conditions. Straw removal of 0%, 50%, and 100% was arranged in a randomized block design with four replications. Dielectric water potential sensors were used to record soil water potential (ψ, kPa) and soil temperature (°C) every 6 h at a 0.15-m depth. Sugarcane yields were measured annually using an instrumented truck equipped with load cells. In general, the complete and partial straw removals were detrimental to water storage and therefore to plant available water causing an increase in soil temperature during sprouting and tillering phases, which are extremely important periods for a good crop establishment and, consequently, for yield increase. For the experimental sites presenting high fertility, greater water holding capacity, high sugarcane yield potential, and considering an extended water deficit in early stages of crop development, the complete straw removal resulted in yield losses of up to 16 and 40 Mg ha−1, respectively. For the experimental site presenting low sugarcane yield potential, even with low water deficit at the beginning of crop seasons, straw removal had no significant influence on sugarcane yield in the short term, since straw did not produce enough improvements to soil in order to enable benefits for water retention.

Prediction of Sugarcane Yield by Soil Attributes under Straw Removal Management

Core Ideas Soil changes induced by short‐term sugarcane straw removal did not influence the crop yield. The yield of sugarcane straw and stalk can be predicted using soil attributes under fields managed with straw removal. Meteorological conditions may alter the straw/stalk ratio and thus influence the sugarcane straw yield. Sugarcane (Saccharum spp.) straw removal from the field has the potential to produce short‐term gains at the cost of long‐term sustainability. The objective of this study was (i) to develop a model capable to predict sugarcane yield (straw and stalk) by soil attributes and (ii) to discover why yields are minimally impacted following straw removal. In this 2‐yr experiment, the sugarcane straw removal effects on crop yields and soil attributes were investigated at two sites, Valparaíso and Capivari, in southeastern Brazil. Soil samples from the 0–5, 0–10, 0–20, and 0–30 cm were analyzed for C, N, Ca, Mg, P, K, pH, bulk density (BD), and soil penetration resistance (PR). The data were subjected to descriptive statistical, geostatistical, correlation and regression analyses. The findings showed that the straw and stalk yield can be predicted using soil attributes data at sites where the straw is removed. The best modeling coefficients for stalk yield were obtained using soil data from the 0–20 cm layer. The straw removal induced reduction in soil C, chemical and physical quality (0–5 cm) depending on site, but did not result in lower yields. The research findings provide important information that will lead to sustainable bioenergy production in Brazil.

Sugarcane straw removal effects on soil water storage and drainage in southeastern Brazil

To enhance global bioenergy production, the Brazilian industry9s interest in using sugarcane (<i>Saccharum officinarum</i>) straw as a feedstock for electricity and cellulosic ethanol production has increased recently. However, indiscriminate straw removal may negatively affect key soil functions related to water infiltration, retention, and availability to plants. Therefore, a microlysimeter system with a 0.2 m soil column was built to evaluate the effects of straw removal rates on water drainage and water storage in a sandy clay loam soil from a commercial sugarcane field in southeastern Brazil. The experiment was conducted in an open area where the lysimeter system was subjected to rainfall. After assembly, the treatments consisting of four straw amounts of 0, 3, 6, and 12 Mg ha⁻¹ were applied, representing straw removal rates of 100% (bare soil), 75%, 50%, and 0%, respectively. The water drainage was quantified and collected for 17 months, and the soil water storage was measured over a two-month period. The soil water holding capacity was calibrated by an inverse modeling approach minimizing the differences between soil water storage measured in the field and simulated by a water balance model. Our results reveal that the amount of water drained from bare soil was 30% lower than no removal treatment. Bare soil had the lowest water storage for most of the days, indicating a greater susceptibility to losing water through evaporation and drying. The long-term simulation for early, mid, and late sugarcane harvest seasons suggests longer periods of water restriction to crop growth under higher straw removal rates (i.e., 100% and 75%), potentially impairing sugarcane growth and thus yield. Also, the findings suggest that partial residue maintenance, up to 6 Mg ha⁻¹ of straw (50% removal) on the soil surface, seems to be sufficient to prevent excessive water losses and daily variations of soil water content, sustaining soil water storage rates above the critical point for sugarcane growth.

Soil physical quality response to sugarcane straw removal in Brazil: A multi-approach assessment

Crop residues have an essential role in sustaining soil functions and the removal of sugarcane straw for bioenergy production can exacerbate the adverse impacts of mechanized harvesting on soil quality. A long-term field experiment was carried out to evaluate the effects of straw removal on soil physical quality in southern Brazil. We performed a multi-approach assessment including quantitative physical indicators (bulk density–BD; soil resistance to penetration–SRP; macroporosity–MaP; microporosity–MiP; mean weight diameter of aggregates–MWD), biological indicator (earthworm abundance), apparent electric conductivity (ECa) and visual evaluation of soil structure (VESS). In addition, VESS scores were correlated with quantitative indicators for testing its potential as a feasible integrative soil quality indicator. Straw removal rates (total removal, TR–0 Mg ha−1; high removal, HR–5 Mg ha−1; low removal, LR–10 Mg ha−1; no removal, NR–15 Mg ha−1) were arranged in a randomized block design with four repetitions. Except for MaP, straw removal for four years affected all soil physical attributes, with higher soil degradation observed in TR and HR plots. Soil moisture, earthworm abundance and ECa values were reduced by higher rates of straw removal. The VESS method was able to detect the changes in soil structural quality, and VESS scores averaged 4.5 and 3.9 for the TR and HR plots respectively, thus revealing signals of severe structural degradation. The data also showed that VESS scores correlated with quantitative indicators broadly used for soil assessments, which suggest VESS as a reliable and integrative indicator for monitoring soil structural quality in sugarcane fields. Our findings support that LR, keeping about 10 Mg ha-1 of straw on the soil surface, can be a management target to ensure the sustainability of bioenergy production.

Sugarcane yield and soil carbon response to straw removal in south-central Brazil

Understanding the impacts of straw removal on quantity and quality of soil organic carbon (SOC) is crucial for sustaining or improving soil functions and producing economically viable sugarcane yields. Field experiments were carried out on commercial farms to quantify effects of straw removal on sugarcane yields, SOC stocks and the degree of soil organic matter (SOM) humification under three diverse edaphoclimatic conditions (Quirinópolis-GO, Chapadão do Céu-GO and Quatá-SP) in Brazil, while considering the effects of cover crop on sugarcane yields during two harvest seasons. Three straw removal rates (0, 50, and 100%) were arranged in a randomized block design with four replications within two paired areas, one seeded with Crotalaria spectabilis (cover crop–CC) and the other kept under bare fallow (BF) during the sugarcane-replanting period. Sugarcane yields were measured annually using an instrumented truck equipped with load cells, and soil samples were collected to a depth of 40-cm two years after establishing the trials. Straw removal for two years did not significantly influence cane yields in Quatá-SP, but in Chapadão do Céu-GO and Quirinópolis-GO, complete straw removal resulted in cumulative yield losses of up to 28 and 62 Mg ha−1 respectively. The inclusion of Crotalaria spectabilis within sugarcane cropping cycle increased two-year cumulative yields by 25 and 27 Mg ha−1 in Chapadão do Céu-GO and Quirinópolis-GO respectively. SOC response to straw removal was highly site-specific after two years. In fine-textured soils, straw removal rates did not significantly affect SOC stocks in Chapadão do Céu-GO, but in Quirinópolis-GO complete straw removal favored the depletion of SOC stock relative to partial or no straw removal in both soil layers (0–10 and 0–40 cm) of the BF area, while within the CC area SOC depletion was observed in the 0–40 cm layer. For sandy soil (Quatá-SP), complete straw removal decreased SOC stock only in the top 10 cm of the CC area. Laser-Induced Fluorescence Spectroscopy showed high degree of SOM humification in soils with depleted SOC stock, indicating that excessive straw removal was degrading soil quality by reducing the amount of labile C in the SOM. Conclusions drawn from this study indicate that, even on a short-term basis, complete straw removal already began to modify the quantity and quality of SOC, while both moderate or complete removals adversely affected sugarcane yields.

Sugarcane straw removal effects on plant growth and stalk yield

There is growing interest in sugarcane straw removal from the field to use as raw material for bioenergy production. In contrast, sugarcane straw removal may have negative implications for many soil ecosystem services and subsequent plant growth. A two-year experiment was conducted at Bom Retiro and Univalem mills within the dry and wet seasons for assessing the impact of straw rates removal on plant production. The experimental design was randomized blocks with five treatments proportional to 0, 25, 50, 75 and 100% of straw removal. Plant parameters evaluated included: tillering, phytomass accumulation, stalk yield and stalk industrial quality. Straw removal increased plant tillering at Bom Retiro mill in both seasons and within dry season at Univalem mill, however the plant population at the end of each ratoon cycle was not affected by straw management. Phytomass yield across each ratoon cycle was fit to a sigmoidal model (R2≥0.92, p<0.05). Time necessary for plant completes its lag-phase is higher at the treatments applied in the dry season, whereas there was no time-pattern for plants to complete the linear and stationary growth phases. Moderate amounts of straw: 4–9Mgha−1 (dry base) on soil surface enhanced stalk yield. Different rates of straw removal did not affect stalk industrial quality. Overall, partial straw removal, at least in the short-term, could be a win–win situation, sustaining sugarcane yields and providing feedstock for bioelectricity cogeneration and/or 2G-ethanol production.

Sugarcane straw removal effects on Ultisols and Oxisols in south-central Brazil

The maintenance of sugarcane straw on the field has an important role in preserving the soil properties and organic carbon content. However, there is a growing interest in removing part of this residue to use in bioenergy production. The effect of straw removal on soil quality is still poorly studied. The aim of this study was to evaluate the impact of short-term (2years) straw removal from soil surface on soil quality. Two experiments were carried out in São Paulo state, Brazil: one in an Oxisol (sandy clay loam soil) and another in an Ultisol (sandy loam soil). We have tested five rates of straw removal (i.e., equivalent to 0, 25, 50, 75 and 100%). Soil samples were taken from 0 to 2.5, 2.5–5, 5–10, 10–20 and 20–30cm layers to analyze pH, total C and N, P, K, Ca, Mg, bulk density and soil penetration resistance. The effects of straw removal were limited to the soil surface layer and differed between the two types of soil. Under the Oxisol, the straw removal favored soil physical degradation (i.e., increased soil compaction and resistance to penetration) and depletion of soil C stocks. On the other hand, straw removal management only affected chemical properties in the Ultisol, reducing nutrient contents (e.g., Ca and Mg). Based on a multivariate analysis that involving all attributes, the sandy texture soil (Ultisol) showed more sensitivity to straw removal management, even over this short period (2years), in which the removal of any amount of straw caused a negative impact on soil quality. In contrast, in the sand-clay-loam soil (Oxisol) the removal rate of up to 50% of the straw (i.e., the maintenance of ~ 8.7Mgha−1 of straw on soil surface) proved to be sustainable. Therefore, sugarcane straw removal should be site-specific, taking into account intrinsic soil properties and climate conditions, which preventing soil degradation and negative impacts on the provision of multiple ecosystem services. This guarantees the sustainability of the Brazilian bioenergy production.

Irrigated Small-Grain Residue Management Effects on Soil Chemical and Physical Properties and Nutrient Cycling

The effects of straw removal from irrigated wheat and barley fields cropped to wheat and barley on soil properties and nutrient cycling is a concern due to its potential impact on the sustainability of agricultural production. Increasing demand of straw for animal bedding and the potential development of cellulosic ethanol production will likely increase the demand in the future. Previous reviews addressing changes in soil properties when crop residues are removed focused primarily on rain-fed systems. This paper reviews published research assessing the effects of wheat and barley straw removal on soil organic carbon (SOC), and analyzes changes in nutrient cycling within irrigated wheat and barley production systems. The effects of straw removal on bulk density (BD), saturated hydraulic conductivity, and other properties are reported from selected studies. Six studies compared SOC changes with time in irrigated systems in which wheat straw was removed or retained. These studies indicated that SOC either increased with time or remained constant when residues were removed. It is possible that belowground biomass is supplying C to soils at a rate sufficient to maintain or in some cases, slowly increase SOC with time. A separate research review calculated the minimum aboveground residue required to maintain SOC levels (MCS) from nine wheat system studies. Calculations of the MCS values were from rain-fed systems and are some of the best information available presently for use in evaluating residue removal effects in irrigated systems. However, long-term studies are needed to obtain reliable data for diverse irrigated systems. Nutrients removed from the soil/plant system with straw can be worth $7 to $20 per Mg of straw removed. Producers will need to determine the cost of the nutrient removal from their systems to determine the value of the straw.

Effect of straw management, tillage timing and timing of fertilizer nitrogen application on the crop utilization of fertilizer and soil nitrogen in an irrigated cereal rotation

In irrigated grain-growing soils on Canada's prairies, straw management can affect nitrogen (N) fertility and long-term soil organic matter reserves. We conducted a 2-year field experiment in southern Alberta, on a Dark Brown Chernozemic Lethbridge loam (Typic Boroll), to determine the effects of straw removal, tillage, and fertilizer timing on crop uptake of soil and fertilizer N. During the study (1991 and 1992), the crop was oat ( Avena sativa L.) and wheat ( Triticum aestivum L.), respectively, in an experiment that had been in a wheat-wheat-oat-wheat rotation since 1986. Five straw-tillage treatments were: straw-fall plow, straw-pring plow, no straw-fall plow, no straw-spring plow and no straw-direct seeding. Fertilizer N was applied in fall or spring. Ammonium nitrate (5 at.% 15N) was added at 100 kg N ha −1 in fall 1990 or spring 1991. For oat (1991), plant N derived from soil was higher under fall plow than under spring plow, higher with tillage than direct seeding, and unaffected by straw removal. The plant N derived from fertilizer was not affected by straw removal in fall plow treatments, but under spring plow, it was higher with straw removal. The plant N derived from fertilizer showed a significant straw-tillage × fertilizer timing interaction; with fall incorporated straw, plant N derived from fertilizer was 44.0 kg N ha −1 for spring-applied, and 30.6 kg N ha −1 for fall-applied N, but in other straw-tillage treatments there was no effect of fertilizer timing. Cumulative fertilizer N recovery (plant + soil) over the 2 years averaged 64.2%, and was unaffected by straw-tillage treatment. Fertilizer N recovery, however, was less with fall-applied N (61.3%) than spring applied N (66.8%). At mid-season, fall plow treatments had higher soil inorganic N and inorganic N derived from fertilizer than spring plow treatments, apparently because of less immobilization. The fall plow treatments also retained higher inorganic N after harvest. Straw removal and fertilizer timing did not influence soil inorganic N and soil inorganic N derived from fertilizer. N removal in straw (16 kg N ha −1 yr −1) could deplete soil N in the long-term. Long-term effects of tillage timing on soil N will depend on the relative amount of N lost by leaching with fall plowing and that lost by denitrification under spring plowing. With direct seeding, crop yield and uptake of soil N was less, and N losses by denitrification could be greater. Application of N in spring, rather than fall, should enhance crop N uptake, reducing N losses and enhancing long-term soil organic N.