Amount Of Crop Residues Research Articles

Use of Urea Treated Crop Residue in Ruminant Feed

Large amounts of crop residues are produced annually globally which are hitherto rendered waste. Various farm wastes i.e. crop residue have been effectively, efficiently and economically employed in form of all-inclusive diets. This study summarizes the importance of this waste to ruminant animals especially in developing nations where there is major feeding requirements constraint mostly during the dry seasons of the year. The all-inclusiveness of these residues are created by treating and fortifying these wastes with technologies highlighted in this review. The development and improvement of the quality of this fibrous crop residue is the main thrust of this study through nutrient balancing and amend major nutritional flaws inherent in them. Few practical ways were mentioned and described, others ways to harvest more gains from crop residues were highlighted.

Annual emissions of air toxics emitted from crop residue open burning in Southeast Asia over the period of 2010–2015

Southeast Asia (SEA) has large agricultural crop production and huge amounts of crop residues generated annually are commonly burned in the field to quickly clear land for the next crop planting. This study developed annual emission inventory for crop residue open burning (CROB) covering 17 emission species/groups for 10 SEA countries during 2010–2015, illustrated with relative contributions by country and by crop type. The fractions of crop residue subjected to open burning (OB), a large source of uncertainty in the activity data, compiled from surveys in SEA were significantly higher than those suggested in international databases. Emission factors for rice and maize residue OB were obtained from field experiments conducted in Thailand. The best estimates of the annual emissions averaged over 6 years, of air toxics were: 32 Gg of polycyclic aromatic hydrocarbons, 0.03 Gg organo-chlorinated pesticides, 292 Gg total chlorines, and 94 g I-TEQ dioxins. Emissions of PM2.5, BC and OC, in Tg yr−1, were respectively 1.8, 0.08 and 0.8. The coefficients of variation of annual emissions during the period were relatively small (2.6–8.6% depending on species) but still showed an increasing trend that reflected the changes in production of major crops during the period. Regionally, CROB shared 10–43% of the total biomass open burning emissions but varying with country: by far dominant in Vietnam and Philippines, and much less dominant in Indonesia, Myanmar, and Thailand. Rice straw open burning was the most dominant (19–97%) in the total CROB emissions of the 8 considered crops. The spatial distributions of annual emissions (0.1° x 0.1°) showed higher emission intensity over the areas cultivated with rice and sugarcane, while higher monthly emissions coincided with major harvesting periods in the dry season. The obtained EI data can be further used for air quality modeling to assess effects of CROB emission and to promote non-OB alternatives in the region.

Impact of crop residue management on crop production and soil chemistry after seven years of crop rotation in temperate climate, loamy soils.

Society is increasingly demanding a more sustainable management of agro-ecosystems in a context of climate change and an ever growing global population. The fate of crop residues is one of the important management aspects under debate, since it represents an unneglectable quantity of organic matter which can be kept in or removed from the agro-ecosystem. The topic of residue management is not new, but the need for global conclusion on the impact of crop residue management on the agro-ecosystem linked to local pedo-climatic conditions has become apparent with an increasing amount of studies showing a diversity of conclusions. This study specifically focusses on temperate climate and loamy soil using a seven-year data set. Between 2008 and 2016, we compared four contrasting residue management strategies differing in the amount of crop residues returned to the soil (incorporation vs. exportation of residues) and in the type of tillage (reduced tillage (10 cm depth) vs. conventional tillage (ploughing at 25 cm depth)) in a field experiment. We assessed the impact of the crop residue management on crop production (three crops—winter wheat, faba bean and maize—cultivated over six cropping seasons), soil organic carbon content, nitrate (n}{}{mathrm{NO}}_{3}^{-}), phosphorus (P) and potassium (K) soil content and uptake by the crops. The main differences came primarily from the tillage practice and less from the restitution or removal of residues. All years and crops combined, conventional tillage resulted in a yield advantage of 3.4% as compared to reduced tillage, which can be partly explained by a lower germination rate observed under reduced tillage, especially during drier years. On average, only small differences were observed for total organic carbon (TOC) content of the soil, but reduced tillage resulted in a very clear stratification of TOC and also of P and K content as compared to conventional tillage. We observed no effect of residue management on the n}{}{mathrm{NO}}_{3}^{-} content, since the effect of fertilization dominated the effect of residue management. To confirm the results and enhance early tendencies, we believe that the experiment should be followed up in the future to observe whether more consistent changes in the whole agro-ecosystem functioning are present on the long term when managing residues with contrasted strategies.

Nitrous oxide mitigation potential of reduced tillage and N input in durum wheat in the Mediterranean

In Italy, managed soils account for about 50% of annual national emissions of nitrous oxide (N2O), thus the effect of agricultural practices on N2O emissions must be studied in order to develop mitigation strategies. Soil N2O emissions were measured in two field campaigns (2013–2014 and 2014–2015) on durum wheat in a Mediterranean environment to test the mitigation potential of reduced tillage and nitrogen (N) fertilization rate. N2O emissions were measured with a fully-transportable instrument developed during the project LIFE + IPNOA “Improved flux Prototypes for N2O emission reduction from Agriculture” and equipped with an infrared laser detector. Reducing tillage from ploughing to minimum tillage had no effect on average daily N2O flux, while decreasing the N rate from 170 to 110 kg N ha−1 reduced the average daily N2O flux, without negatively affecting the grain yield. Furthermore, N2O daily flux were positively correlated with soil water filled pore space, NO3-N, and NH4-N concentrations, and they were largely variable between the two field campaigns as a result of different environmental and management conditions (i.e.: rainfall, different amount of crop residues incorporated in soil). Overall, the innovative fully-transportable instrument performed well in the field and allowed us to conclude that decreasing the N fertilizer rate was a valuable option to mitigate N2O emissions without negative effects on wheat productivity.

Degradation of Rice Straw with Microbial Consortium

Rice cultivation generates large amount of crop residues in which only 20% is utilised for industrial and domestic purpose. In developing countries especially in India, rice straw is used as part of feeding ingredient for the ruminants, however, due to its low protein content and high level of lignin and silica it has limited digestibility and nutrient value. For ultimate utilisation there is a need to improve its nutrient and promote its utilisation through ensiling. The factors that influence quality of silage depend upon the fermentation process used to enhance the nutrient recovery and improve in silage stability. This review emphasises in various aspects of silage process and microbial additives in order to improve fermentation of rice straw.

Influence of Cover Crop and Tillage Systems on Optimal Nitrogen Rate for Tennessee Cotton Considering Risk

Upland cotton fields have minimal amounts of crop residue after harvest to cover the soil surface, which exposes the soil and increases the risk of soil erosion. This is especially challenging in the Mid-South U.S. where cotton is commonly grown on sandy or silty soils that are naturally prone to soil erosion. Winter cover crops and no-till planting are two practices that can mitigate soil erosion by increasing soil surface biomass. However, there is uncertainty on how these practices can impact producers’ profits and risk. We determine the influence of four winter cover crops and two tillage systems on the optimal nitrogen rates, cotton yields, and net returns for risk-neutral to risk-averse cotton producers. Data came from a long-term nitrogen (N), tillage, and cover crop experiment in Tennessee. A flexible moment model was used to estimate the impact of risk on the decision to plant cover crops and tillage system. Planting cover crops on till planted cotton decreased optimal N fertilizer rate as well as optimal yields. However, the impact of cover crops on optimal N rate, yields, net returns for no-till planting depends on the cover crop species. A risk-neutral producer would select a till and no cover crop system, but as risk aversion increases, no-till planting with no cover crop system was optimal. Results improve the understanding into the profitability and risk of using cover crops and no-till, which will assist producers in making optimal production systems.

Germination ecology of Sonchus oleraceus L. in the northern region of Australia

In Australia, Sonchus oleraceus has been emerging as a major weed in conservation agricultural systems. The effect of environmental factors on germination and emergence of S. oleraceus was assessed on populations collected from Gatton (SOG) and St. George (SOS) regions of Australia, which are high and low rainfall regions respectively. Germination of both populations responded similarly to various environmental factors studied. Although S. oleraceus seeds germinated under a broad range of temperatures (15/5, 20/10, 25/15 and 30/20°C day/night), germination was lower at 15/5°C. There was only 47–53% germination under dark conditions compared with 62–87% under alternating light–dark. Germination was only 2 and 3% at –0.8 MPa osmotic potential for SOG and SOS populations respectively, and no germination occurred at –1 MPa. Germination was 6 and 8% at 200 mM NaCl for SOG and SOS populations respectively. Although S. oleraceus seed germination exceeded 80% for pH 6–7, germination was reduced at pH outside this range. Germination was 83 and 87% for SOG and SOS populations respectively at the soil surface; and emergence decreased with increasing depth, with none from seeds buried at 6 cm depth. Wheat residue amount within the range of 0–2000 kg ha–1 did not alter germination; however, germination was significantly reduced when the crop residue amount increased to 4000 kg ha–1 and the lowest germination was at 6000 kg ha–1. The potential to germinate under diverse environmental conditions correlates with the widespread occurrence of this weed in the northern region of Australia. High residue amounts and occasional tillage leading to deep burial of seeds may reduce its emergence and incidence.

Japanese Foxtail (Alopecurus japonicus) Management in Wheat in China: Seed Germination, Seedling Emergence, and Response to Herbicide Treatments

AbstractLittle information is published related to seed germination and seedling emergence of Japanese foxtail, a troublesome annual grass weed widely distributed in winter wheat fields in China. Three Japanese foxtail populations were studied under laboratory and greenhouse conditions, to determine the effects of different environmental factors on seed germination or seedling emergence. Chemical control is absolutely necessary in integrated management, and efficacy of POST herbicides against different growth stages of Japanese foxtail was evaluated. Germination rate was 90% or more when temperature ranged from 5 to 25 C, with germination onset shortened as temperature increased. Light was not required for germination to occur. For pH values ranging from 5 to10 there was no effect on seed germination. Japanese foxtail seed germination was sensitive to osmotic stress and completely inhibited at an osmotic potential of -1.1 MPa. The ‘1513’ population of Japanese foxtail demonstrated tolerance to soil salinity, with 98% germination at 80 mM NaCl compared with 25 and 40% germination for populations ‘1532’ and ‘1544’, respectively. High amounts of crop residue (10 t ha−1) suppressed Japanese foxtail emergence 38 to 55%. Germination of seeds placed at 160 C for 5 min was completely inhibited for dry seeds, with a similar effect at 130 C for pre-soaked seeds. Seed burial in the soil from 0 to 4 cm had no effect on seedling emergence, but burial at 7 cm completely inhibited seedling emergence. POST herbicides mesosulfuron-methyl (13.5 g ai ha−1), clodinafop-propargyl (67.5 g ai ha−1), pyroxsulam (13.5 g ai ha−1), pinoxaden (67.5 g ai ha−1) and isoproturon (1125 g ai ha−1) reduced plant dry weight 80% or more when applied at three- to seven-leaf stage, but control declined with application at later growth stages. The information from this study helps to develop an integrated approach to Japanese foxtail management.

Cover Crop Residue Amount and Quality Effects on Soil Organic Carbon Mineralization

Decline in soil organic carbon (SOC) and the associated impacts on crop production under conventional farming raises concerns on how alternative management practices increase SOC sequestration and improve agricultural sustainability. This study aimed to understand SOC mineralization kinetics with different cover crop (CC) residue amendments. Soil samples were collected from a fallow and three CC (pea, oat, and canola) plots. Soil samples from the CC plots were manipulated with zero, five, and 10 Mg ha−1 of the respective CC residues. All soil samples were incubated for eight weeks, SOC mineralization was monitored, and the first order kinetic and parabolic equation models were fitted to the observed data for estimating labile SOC (C0), and the decomposition rate constant (k). Subsequent comparisons of fitted model parameters were based on the first order kinetic model. The C0 varied with the residue amount while k varied with CC type. C0 was 591–858% greater with 10 Mg ha−1 and 289–456% greater with five Mg ha−1 residue additions while k was 122–297% greater with 10 Mg ha−1 and 94–240% greater with five Mg ha−1 residue additions when compared to the fallow treatment. The CC residue stimulated cumulative carbon mineralization (Cmin) irrespective of CC type, suggesting that cover cropping has potential to improve SOC cycling in agroecosystems.

Is mulching an efficient way to control weeds? Effects of type and amount of crop residue in rainfed rice based cropping systems in Madagascar

Weeds are a major constraint to crop yields in tropical production systems, especially for smallholder farmers who cannot afford to purchase herbicides. It has been argued that the practice of mulching with crop residues can suppress weeds in conservation agriculture systems. However, few data are available on the effect of crop residue mulching on weed infestation. In this study we quantified the effect of increasing amounts of surface crop residues on weed emergence, weed biomass production and rice yield. The experiment was conducted during four growing seasons in the Lake Alaotra region, Madagascar. Two types of mulch were applied on a no-tilled soil, Stylosanthes guianensis and a mixture of maize and Dolichos lablab, with different amounts ranging from 0 to 45Mg dry matter ha−1. Weed emergence was measured every week from the day of the first rain that triggered weed germination to 100days thereafter, and weed biomass was monitored at four dates during the cropping season. Our results show that weed emergence and weed biomass decreased with increasing amount of residue. More than 10Mgha−1 was, however, needed to significantly reduce weed emergence and weed biomass as compared to the bare soil treatment without surface residues. Rice grain yields decreased by 16% for an increase in weed biomass of one Mgha−1. Our results indicate that mulching is not a viable option of weed control for smallholder farmers, given the low amounts of residue currently retained on their fields, which is at best about 4Mgha−1 in the case of a stylosanthes crop and about 5Mgha−1 in case of dolichos intercropped with maize.

Genotype by tillage interaction and performance progress for bread and durum wheat genotypes on irrigated raised beds

Agronomic systems based on zero tillage and residue retention are becoming more important due to their potential for climate change adaptation through the reduction of soil erosion and improved water availability. Denser soil surface conditions and large amounts of crop residues, however, may be a constraint for early plant establishment, especially in irrigated production areas with high yield potential. Genotype by tillage interactions for yield are not well understood and it is unknown whether tillage should be an evaluation factor in breeding programs.Twenty-six CIMMYT bread (Triticum aestivum) and durum (Triticum turgidum) wheat genotypes, created between 1964 and 2009, were tested for yield and agronomic performance at CIMMYT’s experimental station near Ciudad Obregon, Mexico, over six years. Treatments included conventional and permanent raised beds with full and reduced irrigation. The objectives were to study breeding progress in distinct agronomic systems and to elucidate the importance of tillage and genotype by tillage interaction for yield and agronomic traits.Breeding progress was achieved irrespective of agronomic treatment. Tillage influenced plant growth and number of grains per m2 in both wheat types. In bread wheat, genotype by tillage interaction was significant for yield, test weight, and growth parameters. However, no cross-over effects were detected and rank changes were small. In durum wheat, genotype by tillage interaction was only significant for plant growth. The results do not indicate the need for separate breeding programs. However, the question of a need for selection under zero tillage to increase breeding progress is yet to be answered.

Dynamics of major air pollutants from crop residue burning in mainland China, 2000–2014

Based on satellite image data and China’s Statistical Yearbooks (2000 to 2014), we estimated the total mass of crop residue burned, and the proportion of residue burned in the field vs. indoors as domestic fuel. The total emissions of various pollutants from the burning of crop residue were estimated for 2000-2014 using the emission factor method. The results indicate that the total amount of crop residue and average burned mass were 8690.9Tg and 4914.6Tg, respectively. The total amount of emitted pollutants including CO2, CO, NOx, VOCs, PM2.5, OC (organic carbon), EC (element carbon) and TC (total carbon) were 4212.4–8440.9Tg, 192.8–579.4Tg, 4.8–19.4Tg, 18.6–61.3Tg, 18.8–49.7Tg, 6.7–31.3Tg, 2.3–4.7Tg, and 8.5–34.1Tg, respectively. The emissions of pollutants released from crop residue burning were found to be spatially variable, with the burning of crop residue mainly occurring in Northeast, North and South China. In addition, pollutant emissions per unit area (10 km × 10 km) were mostly concentrated in the central and eastern regions of China. Emissions of CO2, NOx, VOCs, OC and TC were mainly from rice straw burning, while burning of corn and wheat residues contributed most to emissions of CO, PM2.5 and EC. The increased ratio of PM2.5 emissions from crop residue burning to the total emitted from industry during the study period is attributed to the implementation of strict emissions management policies in Chinese industry. This study also provides baseline data for assessment of the regional atmospheric environment.

Crop residue harvest impacts wind erodibility and simulated soil loss in the Central Great Plains

AbstractCrop residue removal can affect the susceptibility to soil wind erosion in climates such as those of the Central Great Plains, United States. Six on‐farm trials were conducted in Kansas from 2011 to 2013 to determine the effects of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor (L.) Moench), residue removal at 0, 25, 50, 75, and 100% of initial height on soil wind erosion parameters. Those parameters include soil surface random roughness (RR), and wind erodible fraction (EF; aggregates <0.84 mm), geometric mean diameter (GMD) and geometric standard deviation (GSD), stability of dry aggregates (DAS). Complete (100%) residue removal decreased the surface RR, increased EF, and decreased GMD. Overwinter EF values increased for five of six sites from fall 2011 to spring of 2012, particularly for the uppermost removal height (≥75%). Measured EF, GMD, GSD, DAS, and RR were also input into the Single‐event Wind Erosion Evaluation Program (SWEEP) to determine the effect of these parameters on simulated soil loss. The SWEEP simulated the wind velocity needed to initiate wind erosion as well as soil loss under each residue removal height at a wind velocity of 13 m s−1 for three hours. Threshold wind velocity required to initiate wind erosion generally decreased with increasing crop residue removal height, particularly for >75% removal. Total estimated soil loss over the three‐hour event ranged from ≈2 to 25 Mg ha−1, depending on EF, GMD, GSD, RR, and percent crop residue cover. Removing 75% residue increased simulated wind erosion at three of six sites while removing 50% appears sustainable at all six study sites. Findings reinforce the need for site‐by‐site consideration of the potential amount of crop residue that may be harvested while mitigating wind erosion. Study results indicate the value of maintaining residue at >75% of original height.

Long-term no-till as a means to maintain soil surface structure in an agroecosystem transformed into irrigation

The aim of this study was to determine the most appropriate soil management to reduce the structural degradation of soils susceptible to crusting in Mediterranean areas recently transformed into irrigation. A long-term field experiment (LTE) under rainfed conditions was established in 1996 in NE Spain to compare three tillage systems (no-tillage, NT; reduced tillage, RT; conventional tillage, CT). The experiment was transformed to irrigated corn in 2015. In 2015, an adjacent experiment with the same layout was created (short-term experiment, STE) in an area previously managed under long-term NT. The study was carried out during the second corn growing season (i.e. year 2016). Soil samples were collected from 0 to 5cm depth at different dates during corn season. Dry and water-stable macroaggregates and their C concentration, soil organic carbon (SOC) and labile C concentration, soil respiration, bulk density, penetration resistance (PR), water infiltration, macroporosity, microporosity, amount of crop residues and ground cover, corn development, aerial biomass, and grain yield were measured. In LTE and STE tillage led to a breakdown of dry sieved aggregates (of 2–4 and 4–8mm size) in RT and CT, being slowly reconsolidated throughout the corn growing season. However, macroaggregate water-stability did not increase in CT and RT compared to NT due to a lower SOC concentration, making the soil more susceptible to its degradation by the action of water. SOC differences between treatments were more pronounced in LTE than STE given the long-term differential management in the first, which allowed greater accumulation of SOC under NT. In LTE, PR between corn rows was greater under NT than CT and RT and non-significantly different between treatments within the row. In the case of STE, PR increased over time after tillage (CT and RT) to match NT in the last sampling. Crop establishment was slower in CT than NT in LTE highlighting the impact of soil surface degradation on crop development. However, contrarily to the differences in corn yield in 2015, a careful planting in 2016 led to a lack of differences between tillage systems on corn yield. Our results indicate that in areas transformed into irrigation intensive tillage leads to greater susceptibility to soil structural degradation. Thus, in these areas the adoption of conservation agriculture practices such RT and NT enhances soil resilience to degradation processes and ensures an adequate development of the crop.

Carbon budget measurement over 12 years at a crop production site in the silty-loam region in Belgium

Carbon dioxide (CO2) exchanges between crops and the atmosphere are influenced by both climatic and management drivers. In this study, a site at the Lonzée Terrestrial Observatory (candidate ICOS site) in Belgium that had been managed for more than 70 years using conventional farming practices, was monitored over three complete rotation cycles (sugar beet/winter wheat/seed potato/winter wheat) from 2004 to 2016. Continuous eddy-covariance measurements and regular biomass samplings were performed in order to obtain the daily and seasonal Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), Total Ecosystem Respiration (TER), Net Primary Productivity (NPP) and Net Biome Production (NBP). Meteorological data and crop management practices were also recorded.Over the 12 crop seasons, total NEE varied both between and within crop types. Crop type influenced net carbon (C) sequestration, with the seed potato crop exhibiting the smallest C fluxes. Despite differences in CO2 assimilation response to weather variables and in cumulated TER/GPP dynamics, the sugar beet, winter wheat and maize crops had similar seasonal NEE values. The NEE inter-annual variability, both between and within crop types, was explained mainly by the length of the active vegetation period, as well as the cumulated photosynthetic photon flux density and average air temperature during this period.The establishment of the C budget over the 12 years of study showed that NEE was a downward (negative) flux (−4.40±0.05kgCm−2), but NBP was an upward (positive) flux (0.99±0.22kgCm−2). That is, as soon as C exportation at harvest and C importation (manure, slimes) were included in the budget, the site behaved as a C source. The intercrop periods contributed significantly to the total C budget, and the C fluxes generated during these periods were positively related to crop residue amount and temperature. The largest uncertainties about the crop C budget were those relating to biomass measurements. Carrying out a soil C inventory would help to validate the NBP-based estimate of soil C loss.

English

An experiment was conducted at the Agronomic Institute of Parana – IAPAR, at the Experimental Station of the municipality of Santa Tereza do Oeste – PR, in Hapludox of clayey soil. Studies with the use of plants cover crops with vigorous root system in different systems of soil management systems are needed, in order to have a diversity of species capable of producing different amounts of crop residues which by decomposing, can alter the physical attributes and consequently, the productivity of the successor culture. The objective of this study was to evaluate the effect of crambe crop and plant cover crops in succession on the physical characteristics of a Haplortox under no-tillage system. The experimental area has been cultivated under no-tillage system for 18 years. The experimental area consisted of 15 plots, each plot with 20x25 m. In 12 plots, plant cover crops were planted, six species of summer and six of winter and the last three consisted of plots with no-tillage system with gypsum application, no-tillage system with scarification and traditional no-tillage (control) in a completely randomized design. The physical attributes of this soil were soil density (DS), total porosity (PT), microporosity (Micro), macroporosity (Macro) and saturated hydraulic conductivity (Ksat) of the soil in the periods of 2014 (initial characterization of the soil) and 2015 (after crambe culture). The microporosity (0.0-0.1 m layer) and Ksat (all soil layers) presented significant differences between treatments in the period of 2015. Microporosity was lower in the pigeon pea coverage (PP) (36.08%), while the largest occurred in the coverage of crambe C5 (45.38%). The Ksat was higher in the dwarf pigeon pea (DPP) (298.20 mm h-1) and sunn hemp (SH) (163.39 mm h-1) coverage in the 0.0-0.1 m layer. The highest Ksat was observed for crambe C9 (96.81 mm h-1), C8 (74.13 mm h-1), velvet bean (70.95 mm h-1) and C5 (53.94 mm h-1) respectively, in the soil layer of 0.1-0.2 m. Key words: Soil management, soil structure, residues.

Sugarcane mulch C and N dynamics during decomposition under different rates of trash removal

Abstract Sugarcane is a worldwide crop that leaves a considerable amount of crop residues (called trash) on the soil surface each year after green cane harvesting. However, the recent industrial valorization of these residues raises the question of how much trash to leave as mulch after harvest. Here, we studied the decomposition of three different trash quantities (4, 8 and 12 Mg ha −1 ) across five experimental sites from a subtropical climate over one year. We quantified the dry matter (DM), carbon (C) and nitrogen (N) contents of the remaining mulch at one-month intervals for one year after trash addition at all sites. The chemical composition of the trash was characterized by proximate analysis at one site. Our results showed that mulch degradation was proportional to the initial amount of trash left on the soil surface, i.e., the degradation rates were similar for the three trash treatments at each site, suggesting no limiting factor to decomposition associated with trash quantity and its contact with the soil. On average, 64% of the trash was degraded after 12 months in all treatments, leading to considerable differences in the mass of C degraded after one year (1.2 ± 0.1, 2.3 ± 0.2 and 3.5 ± 0.3 Mg ha −1 for the 4, 8 and 12 Mg ha −1 treatments, respectively). An interaction between trash quantity and site was observed, which translated into more differences in the C degradation rates between sites for the 4 Mg ha −1 trash treatment. The N content of the remaining mulch was rather stable throughout the year, which indicated the efficient use and recycling of N by the decomposing microflora during trash decomposition. These results will help determine the amount of sugarcane trash that should be left on fields to preserve soil C and soil fertility.

Nitrogen, Phosphorus, and Antioxidant Contents in Crop Residues for Potential Cascade Utilization

Crop residues are produced intensively in some places, such as plant factories. These residues have further potential as a source of bioactive compounds. Cascade-approach valorization, an approach to recovering bioactive compounds, energy, and fertilizer, could be used for crop residue recycling. In this study, nitrogen, mineral, and bioactive compound contents in crop residues (tomato, watermelon, broccoli, and others) were investigated. The crop residues contained higher mineral amounts than corresponding edible portions in published data, indicating that they could be utilized as an alternative fertilizer. The nitrogen content also tended to be high, and the nitrogen-to-carbon ratio was around ten for the tomato residue. Dilution of nitrogen might be required before bioconversion process such as methane fermentation. Phenolic concentrations were similar for the crop residue and the edible portion, but carotenoids were more concentrated in the residues, especially for the tomato and broccoli cases. High concentrations of quercetin in the tomato residue and chlorogenic acids in the watermelon residue were also measured. Large amounts of crop residues could therefore be a source of bioactive compounds. Because of the negative effects antioxidants have on microbial activity, extracting bioactive compounds prior to the bioconversion process might be advisable.

Assessment of the energy potential of crop residues and animal wastes in Tanzania

Energy access has a significant contribution to the social, economic and environmental dimensions of the human development. The access to clean and safe energy can improve the human health and quality of ecosystems by reducing the extent of pollution caused by use of inefficient cooking equipments and processes, and by slowing environmental degradation. In this paper Monte Carlo simulation was applied to evaluate the amount of crop residues available which provided the basis for the quantity of energy that can be generated from the crop residues and animal wastes in Tanzania. The amount of crop residues and animal wastes was estimated from the agricultural statistical data obtained from the Food and Agriculture Organization of the United Nations (FAO) from 1961 – 2012. The analysis revealed the bioenergy potential of crop residues in Tanzania to be 5,714 TJ in 2012, which is extremely larger than the installed electric energy generation capacity of 1564 MW in 2013. Besides, the estimation of renewable energy potential of live animals indicated the ability to generate 1,397 TJ/year if exploited. Thus, effective utilization of crop residues and animal wastes without compromising the amount required for the soil fertility and animal feeds can contribute greatly to the access of safe and clean anergy for sustainable development of the rural and urban areas of Tanzania.

Soil shear properties as influenced by straw content: An evaluation of field-collected and laboratory-remolded soils

Following a rice or wheat harvest, a large amount of crop residue (straw) is retained in fields. The straw is often incorporated into the soil in order to increase the soil organic carbon storage and to reduce soil erosion. However, it has become apparent that the incorporated straw can significantly alter soil shear properties, which can dramatically affect energy inputs for tilling and other soil management practices. In this study, laboratory-remolded wheat straw-soil samples were compared with field-collected straw-soil samples; we found high correlations for the cohesion (R2=0.9084) and internal friction angle (R2=0.9548) properties of the samples. Shear tests on rice and wheat straw with different moisture content levels clearly demonstrated the relatively higher shear strength of wheat straw compared to rice straw. The cohesion of remolded rice and wheat straw-soil samples exhibited an increasing linear trend with an increase in densities, whereas the internal friction angle data for these samples exhibited a quadratic trend. Overlapping the cohesion curves revealed that the wheat straw-soil and rice straw-soil samples had the same cohesion at a straw density of 0.63%. Similar results were obtained when the internal fraction angle curves overlapped; the resultant point of intersection was observed at a straw density of 0.46%. As a whole, the remolded sample methodology was found suitable to simulate the shear properties of soils sampled directly from fields.