Amount Of Crop Residues Research Articles

Testing the RothC and DNDC models against long-term dynamics of soil organic carbon stock observed at cropping field soils in North China

RothC and DNDC, two process-based agroecosystem models widely utilized for quantifying soil carbon (C) sequestration, were tested against datasets of soil organic carbon (SOC) measured in two long-term experiments with winter wheat-summer maize rotation at field soils in North China. In the study, the two models were utilized in conjunction in three modes, i.e., using DNDC alone, using RothC driven by soil C inputs of measured crop residue, and using RothC driven by soil C inputs derived from DNDC simulations. In general, results from the three ways of simulations were in agreement with the measured SOC dynamics for the two experimental sites with varied treatments. However, discrepancies in the results revealed the differences between the two models regarding their functionality. The simulations with RothC driven by the measured crop residue as C input produced the best results on SOC dynamics in comparison with observations. Results from the simulations with DNDC alone were less correlated to observations mainly due to the approximation of the modeled amount of crop residue. Due to the same reason, the simulations with RothC but driven by DNDC-modeled crop residue poorly fit to observations. The results conclude that given the similarity between RothC and DNDC regarding their routines modeling SOC transformations it is crucial for improving the models’ performance to provide accurate C input data (mainly crop residue) to the SOC turnover modules in the models.

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.

Current and future technical, economic and environmental feasibility of maize and wheat residues supply for biomass energy application: Illustrated for South Africa

This study assessed the feasibility of mobilising maize and wheat residues for large-scale bioenergy applications in South Africa by establishing sustainable residue removal rates and cost of supply based on different production regions. A key objective was to refine the methodology for estimating crop residue harvesting for bioenergy use, while maintaining soil productivity and avoiding displacement of competing residue uses. At current conditions, the sustainable bioenergy potential from maize and wheat residues was estimated to be about 104 PJ. There is potential to increase the amount of crop residues to 238 PJ through measures such as no till cultivation and adopting improved cropping systems. These estimates were based on minimum residues requirements of 2 t ha−1 for soil erosion control and additional residue amounts to maintain 2% SOC level.At the farm gate, crop residues cost between 0.9 and 1.7 $ GJ−1. About 96% of these residues are available below 1.5 $ GJ−1. In the improved scenario, up to 85% of the biomass is below 1.3 $ GJ−1. For biomass deliveries at the conversion plant, about 36% is below 5 $ GJ−1 while in the optimised scenario, about 87% is delivered below 5$ GJ−1. Co-firing residues with coal results in lower cost of electricity compared to other renewables and significant GHG (CO2 eq) emissions reduction (up to 0.72 tons MWh−1). Establishing sustainable crop residue supply systems in South Africa could start by utilising the existing agricultural infrastructure to secure supply and develop a functional market. It would then be necessary to incentivise improvements across the value chain.

The effects of conservation tillage practices and fertiliser management on soil structural properties at an experimental farm

Crop rotation and reduced tillage under conservation agriculture (CA) practices may induce higher soil organic carbon (SOC) and nitrogen (N) levels compared with conventional (Con) tillage practices. Soil organic carbon may increase soil aggregate stability (AS). The study site was a rain-fed CA field trial with a randomised split-plot design. The effects were evaluated over four experimental seasons of CA and Con on AS, SOC, soil N and on temporal trends of soil properties. Soil aggregate samples were taken annually on plots representing two tillage practices and four fertiliser/crop systems. Standard laboratory and statistical procedures were performed to determine soil properties and to test for relationships between soil properties and differences between treatments. Soil aggregate stability significantly (p<0.001) increased from 90 to 140 cm3 as SOC and total N increased from 11.5 to 21.5 g kg−1 and 0.77 to 1.43 g kg−1, respectively. Reduced tillage increased AS and SOC to 126.6 cm3 and 17.2 g kg−1, respectively, compared with Con. Seasonal trends showed increases of AS and SOC under reduced tillage compared with Con, whereas under both tillage practices increasing trends in total and inorganic soil N were observed. Conservation agriculture practices that retain large quantities of crop residues are recommended to enhance AS.

Evaluating spectral indices for determining conservation and conventional tillage systems in a vetch-wheat rotation

Conservation tillage (CT) systems, which consist of reduced and no-tillage systems, retain considerable quantities of crop residues on the soil surface. These crop residues perform as a barrier to wind and water to decrease soil erosion and evaporation. The use of remote sensing technology provides fast, objective and effective tool for estimating and measuring any agricultural event. The challenge is to differentiate the tillage systems by the crop residue cover on the soil surface. Spectrally derived normalized difference tillage index (NDTI), Shortwave infrared normalized difference residue index (SINDRI), cellulose absorption index (CAI) and Lignin-cellulose absorption index (LCA) were examined to distinguish their value as remote sensing methods for identifying crop residue cover in conventional and conservation tillage systems. Tillage treatments included conventional tillage (MD: Mouldboard plow+Disk harrow), reduced tillage (CD: Chisel plow+Disk harrow), minimum till (MT: Stubble cultivator), and no-tillage (NT1 and NT2: with standing stubble and standing stubble plus threshing residue, respectively).CAI had a linear relationship with crop residue cover, which the comparative intensity of cellulose and lignin absorption features near 2100nm can be measure by it. Coefficients of determination (r2) for crop residue cover as a function of CAI and LCA were 0.89 and 0.79 respectively. Absorption specifications near 2.1 and 2.3µm in the reflectance spectra of crop residues in minimum and no- tillage systems were related to cellulose and lignin. These specifications were not evident in the spectra of conventional tillage system. In this study the best index to use was CAI, which showed complete separation tillage systems, followed by LCA and NDTI. Four tillage intensity classes, corresponding to intensive (<6% residue cover), reduced (10–20% cover) minimum (25–40%) and no-tillage (>60% cover) tillage, were recognized in this study.

Production of 15N-Labelled Liquid Organic Fertilisers Based on Manure and Crop Residue for Use in Fertigation Studies.

Large quantities of crop residue and animal manure from agricultural and livestock activities are annually produced worldwide. With proper management, these residues are potentially valuable sources of plant nutrients, mainly N. Recycling such subproducts in sustainably-based agricultural systems can minimise the use of mineral fertilisers, and hence reduce the potential risk of surface and groundwater pollution. Therefore, the purpose of this study was to obtain (small scale) two liquid labelled-organic fertilisers, an animal- and a vegetal-based organic (AO and VO, respectively) fertiliser, to be used as organic N sources in subsequent fertigation studies. Forage maize (Zea mays L.) grown under 15N-labelled fertiliser supply was used as raw material for VO fertiliser production, and also as 15N-labelled sheep feed to obtain 15N-labelled manure. The labelled faeces fraction was used as raw material for the AO fertiliser. The VO fertiliser was obtained after an acidic and an enzyme-driven hydrolysis. The AO fertiliser was obtained after acidic hydrolysis. The VO liquid fertiliser presented an N concentration of 330 mg·L-1, 85% of total N was organic, while ammonium and nitrate N accounted for 55% and 45% of the mineral nitrogen fraction, respectively. This fertiliser also exhibited high K, Ca and S concentrations and notable values for the remaining macro- and micronutrients. The AO liquid fertiliser had a similar total N concentration (496 mg·L-1, 82% of total N in an organic form) to that of VO, but its mineral N fraction significantly differed, which came in a predominantly (95%) ammonia form. It also had a high content of N, P, K and other macronutrients, and sufficient Fe, Zn, Mn, Cu and B levels, which suggests its suitability as a potential fertiliser. The percentage of 15N enrichment in both VO and AO liquid fertilisers exceeded 2% 15N atom excess, which enabled their use in subsequent assays run to assess nitrogen uptake efficiency.

Windrow Burning Eliminates Italian Ryegrass (Lolium perenne ssp. multiflorum) Seed Viability

Windrow burning is one of several harvest weed seed control strategies that have been developed and evaluated in Australia to address the widespread evolution of multiple herbicide resistance in annual weeds. Herbicide-resistant Italian ryegrass populations are common in the Palouse region of eastern Washington and northern Idaho. Field and greenhouse studies were conducted to evaluate the effects of burning standing stubble and narrow windrows on the survival of Italian ryegrass seed on the soil surface and to determine the amount of crop residue remaining after both practices. Italian ryegrass emergence was 63, 48, and 1% for the nonburned check, burned standing stubble, and burned windrow treatments, respectively. Crop-residue dry weights were 9.94, 5.69, and 5.79 Mg ha−1 for these same treatments. Windrow burning can be an effective tactic in an integrated weed management strategy for Italian ryegrass control in the Palouse region of eastern Washington and northern Idaho.

Soil properties and carbon stocks in a grey Vertosol irrigated with treated sewage effluent

Treated sewage effluent may contain large amounts of nitrogen and phosphorus, and moderate to high amounts of salts. With good management, it can be used as a source of irrigation water and nutrients for a range of crops and soils under different climatic conditions and irrigation systems. However, there are few long-term studies of irrigation with treated sewage effluent in swelling soils such as Vertosols. This study was established in 2000 on a cotton farm near Narrabri, north-western New South Wales, to assess long-term (14-year) changes in soil salinity, sodicity and carbon storage in a self-mulching, medium-fine, grey Vertosol under conservation farming and furrow-irrigated with tertiary-treated sewage effluent and stored rainfall runoff. Experimental treatments in 2000–02 were gypsum applied at a rate of 2.5t/ha in June 2000 and an untreated control. In 2003–13, the gypsum-treated plots received a single pass with a combined AerWay cultivator and sweeps to ~0.15m depth before sowing cotton; in the control plots, wheat stubble was undisturbed. By retaining significant amounts of crop residues on the soil surface, both practices are recognised as conservation farming methods. Parameters for water sampled from the head-ditch during each irrigation included electrical conductivity (ECw), pHw, concentrations of cations potassium (K+), calcium (Ca2+), magnesium (Mg2+) and sodium (Na+), and sodium adsorption ratio (SAR). Parameters for soil sampled to 0.6m depth before sowing cotton were pH (0.01M CaCl2), salinity (EC of 1:5 soil:water suspension), bulk density, soil organic carbon (SOC), exchangeable Ca, Mg, K and Na, exchangeable sodium percentage (ESP) and electrochemical stability index (ESI). SOC storage (‘stocks’) in any one depth was estimated as the product of bulk density, sampling depth interval and SOC concentration. Management system had little or no effect on cotton lint yields and the soil properties measured. Major changes in soil properties were driven by a combination of irrigation water quality and seasonal variations in weather. The cultivated treatment did not degrade soil quality compared with the control and may be an option to control herbicide-resistant weeds or volunteer Roundup-Ready cotton. Irrigation water was alkaline (average pHw 8.9), moderately saline (average ECw 1.0dS/m) and potentially highly dispersive (average SAR 12.1). Long-term irrigation with tertiary-treated sewage effluent resulted in sodification (ESP &gt; 6) at all depths, alkalinisation at 0–0.10 and 0.30–0.60m, and accumulation in the surface 0.10m of Ca and K. Average ESP at 0–0.6m depth increased from 3.8 during 2000 to 13.2 during 2013. Sodification occurred within a few years of applying the effluent. Exchangeable Ca at 0–0.10m depth increased from 19cmolc/kg during 2000 to 22cmolc/kg during 2013, and exchangeable K from 1.5cmolc/kg during 2000 to 2.1cmolc/kg during 2013. Drought conditions caused an increase in salt accumulation, alleviated by a subsequent period of heavy rainfall and flooding. The reduction in salinity was accompanied by a fall in exchangeable Mg concentrations. Salinity and exchangeable Mg concentration were strongly influenced by interactions between seasonal rainfall (i.e. floods and drought) and the quality of the effluent, whereas ESP and exchangeable K concentration were not affected by variations in seasonal rainfall. SOC stocks declined until the flooding events but increased thereafter.

Autumn Maize Intercropped with Tropical Forages: Crop Residues, Nutrient Cycling, Subsequent Soybean and Soil Quality

Autumn maize intercropped with tropical forages can raise the amount of crop residues and improve nutrient cycling, favoring subsequent soybean crop. The objective of this study was to evaluate the effect of forms of implementation of intercropping of irrigated autumn maize with tropical forages on yield, decomposition, nutrient accumulation and release, and on the ratio of lignin/total N of forage residues, yield components, and grain yield of subsequent soybean, and on soil physical and chemical properties, under no-tillage in lowland Cerrado. The experiment was arranged in randomized blocks in a factorial (4 × 3 + 1) design with one control and four replications. The treatments consisted of four forages: Palisade grass, Congo grass, and two Guinea grass cultivars (Tanzânia and Aries); and three methods of sowing intercrops of forage-autumn maize: forage sown simultaneously with maize in the sowing furrow, mixed with fertilizer; forage sown by broadcasting on the day of maize sowing; and forage seeds mixed with fertilizer broadcast on maize in growth stage V4; plus a control (maize monoculture). The decomposition and nutrient release rate of the forage residues were evaluated by the litter bag method, 30, 60, 90, and 120 days after desiccation. Sowing the forages in the furrow and by broadcasting raise the total amount of maize residues compared to method V4. Regardless of the forage type and sowing methods, intercropping increases the amount of residues compared to maize monoculture. The forages and sowing methods had no influence on nutrient accumulation in the residues at the time of desiccation and at the lowest lignin/total N ratio in Congo grass residues, and a logarithmic decay was observed. Forage and sowing methods did not influence the macronutrient release rate from crop residues for 120 days after desiccation; the release of N, P, K and Mg is logarithmic and the release of Ca and S exponential. Forage and sowing methods do not influence yield components and grain yield of subsequent soybean. However, intercropping increased grain yield of subsequent soybean compared to soybean after maize monoculture, and preserved the soil chemical and physical properties.

Fermentation Quality and Additives: A Case of Rice Straw Silage.

Rice cultivation generates large amount of crop residues of which only 20% are utilized for industrial and domestic purposes. In most developing countries especially southeast Asia, rice straw is used as part of feeding ingredients for the ruminants. However, due to its low protein content and high level of lignin and silica, there is limitation to its digestibility and nutritional value. To utilize this crop residue judiciously, there is a need for improvement of its nutritive value to promote its utilization through ensiling. Understanding the fundamental principle of ensiling is a prerequisite for successful silage product. Prominent factors influencing quality of silage product include water soluble carbohydrates, natural microbial population, and harvesting conditions of the forage. Additives are used to control the fermentation processes to enhance nutrient recovery and improve silage stability. This review emphasizes some practical aspects of silage processing and the use of additives for improvement of fermentation quality of rice straw.

GERMINACIÓN Y EMERGENCIA DE Megathyrsus maximus VAR.maximus

RESUMEN Se estudió la germinación de semillas de Megathyrsus maximus al exponerlas a altas temperaturas y el efecto de diferentes profundidades de siembra y cantidades de residuos de cosecha en la emergencia de las plántulas. En laboratorio, se determinó la germinación y biomasa de semillas con y sin glumas y glumelas, expuestas a 0, 40, 60, 80 y 100 oC durante cinco minutos. Se realizaron dos experimentos en invernáculo para evaluar la emergencia de la maleza, primero a diferentes profundidades de siembra: 0, 0.5, 1, 2, 3, 4, 5, 7 y 8 cm. Posteriormente, se evaluó emergencia con diferentes cantidades de residuos de cosecha: 0, 5, 8, 11, 13, 15 y 18 t ha-1. Los resultados de los ensayos de temperatura se analizaron mediante análisis de covarianza y los datos de los ensayos de invernáculo mediante regresión. Los máximos porcentajes de germinación para semillas con y sin glumas y glumelas se obtuvieron a 40 oC y fueron del 35 y 48%, respectivamente; los mínimos valores se registraron a los 80 oC y fueron del 7 y 28%, respectivamente. La profundidad de siembra afectó la emergencia: un 51% se registró en el testigo, valor que disminuyó al 23,3% a los 7 cm y a 0% a los 8 cm. Los residuos de cosecha también afectaron la emergencia: con 0 a 18 t ha-1, esta disminuyó del 64,8 al 0%. Puede concluirse que las estrategias implementadas en el manejo del cultivo de caña de azúcar afectarán la germinación y emergencia de M. maximus

Remote sensing to monitor cover crop adoption in southeastern Pennsylvania

In the Chesapeake Bay Watershed, winter cereal cover crops are often planted in rotation with summer crops to reduce the loss of nutrients and sediment from agricultural systems. Cover crops can also improve soil health, control weeds and pests, supplement forage needs, and support resilient cropping systems. In southeastern Pennsylvania, cover crops can be successfully established following corn (Zea mays L.) silage harvest and are strongly pro- moted for use in this niche. They are also planted following corn grain, soybean (Glycine max L.), and vegetable harvest. In Pennsylvania, the use of winter cover crops for agricultural con- servation has been supported through a combination of outreach, regulation, and incentives. On-farm implementation is thought to be increasing, but the actual extent of cover crops is not well quantified. Satellite imagery can be used to map green winter cover crop vegetation on agricultural fields and, when integrated with additional remote sensing data products, can be used to evaluate wintertime vegetative groundcover following specific summer crops. This study used Landsat and SPOT (System Probatoire d' Observation de la Terre) satellite imagery, in combination with the USDA National Agricultural Statistics Service Cropland Data Layer, to evaluate the extent and amount of green wintertime vegetation on agricultural fields in four Pennsylvania counties (Berks, Lebanon, Lancaster, and York) from 2010 to 2013. In December of 2010, a windshield survey was conducted to collect baseline data on winter cover crop implementation, with particular focus on identifying corn harvested for silage (expected earlier harvest date and lower levels of crop residue), versus for grain (expected later harvest date and higher levels of crop residue). Satellite spectral indices were successfully used to detect both the amount of green vegetative groundcover and the amount of crop residue on the surveyed fields. Analysis of wintertime satellite imagery showed consistent increases in vegetative groundcover over the four-year study period and determined that trends did not result from annual weather variability, indicating that farmers are increasing adoption of practices such as cover cropping that promote wintertime vegetation. Between 2010 and 2013, the occurrence of wintertime vegetation on agricultural fields increased from 36% to 67% of corn fields in Berks County, from 53% to 75% in Lancaster County, from 42% to 65% in Lebanon County, and from 26% to 52% in York County. Apparently, efforts to promote cover crop use in the Chesapeake Bay Watershed have coincided with a rapid increase in the occurrence of wintertime vegetation following corn harvest in southeastern Pennsylvania. However, despite these increases, between 25% and 48% of corn fields remained without substantial green vegetation over the wintertime, indicating further opportunity for cover crop adoption.

Long-term effect of residue return and fertilization on microbial biomass and community composition of a clay loam soil

SUMMARYA field study was carried out to examine the response of microbial communities of a clay loam soil to long-term (30 years) effects of residue return and fertilization. The experimental design was a split-plot arrangement of treatments, consisting of three residue treatments (crop residues returned at rates of 0, 2500 and 5000 kg/ha) in combination with eight fertilization treatments (control, no fertilizer; N, mineral nitrogen (N) fertilizer; P, mineral phosphorus (P) fertilizer; K, mineral potassium (K) fertilizer; NP, mineral NP fertilizer; NK, mineral NK fertilizer; PK, mineral PK fertilizer; and NPK, mineral NPK fertilizer). Soil microbial communities were characterized by phospholipid fatty acid analysis. Results indicated that the more crop residues were returned, the lower ratio of fungi to bacteria was observed. However, soil microbial biomass was only found to be significantly higher in plots with residues returned at a rate of 5000 kg/ha but not 2500 kg/ha. This suggested there was a threshold for microbial biomass to increase under residue return for the clay loam soil studied. The fertilization effect on soil microbial biomass gradually decreased with increases in the amount of crop residues returned. A significant composition change was observed under N fertilization. Structural equation modelling indicated that soil microbial communities were influenced directly by residue return and indirectly by residue-induced change in ratio of carbon to N and fertilization-induced change in soil pH.

Umidade e temperatura de argissolo amarelo em sistemas de preparo e estádios de desenvolvimento do milho

RESUMO Os sistemas de preparo do solo afetam a quantidade de resíduo vegetal sobre a superfície do solo e, consequentemente, sua umidade e temperatura. Objetivou-se avaliar a temperatura e a umidade do Argissolo Amarelo em estádios de desenvolvimento da cultura do milho sob sistemas de preparo mecanizado. O experimento foi conduzido no delineamento em blocos inteiramente casualizados, com quatro repetições, em Petrolina - PE. Os sistemas de preparo do solo foram: sem preparo primário, grade off-set de discos de 0,56 m, grade off-set de discos de 0,61 m, escarificador e arado de aivecas. As leituras de umidade e temperatura foram realizadas ao longo do dia, nos horários de 6; 9; 12; 15 e 18 h, nos estádios de desenvolvimento V3, V8, R3 e R6 do milho. A umidade do solo foi avaliada na camada de 0,00-0,05 m utilizando-se do método gravimétrico, e a temperatura do solo na superfície, utilizando-se de termômetro infravermelho. Os sistemas de preparo do solo e os horários de leitura influenciaram na umidade e na temperatura do solo. Os maiores valores de umidade ocorreram no período da manhã, enquanto a maior temperatura do solo ocorreu na parte da tarde.

Energy Generation Potential in Greece From Agricultural Residues and Livestock Manure by Anaerobic Digestion Technology

Greece is an agricultural country producing a significant amount of crop residues as well as livestock manure. The use of agricultural waste as a major component of renewable energy is suitable for improving energy security. Thus, studying the energy generation potential of these wastes is important. The theoretical annual potential of agro-industrial residues (such as wheat products, industrial plants, potatoes, vegetables, olives, fruits, nuts, dairy products etc.) was estimated equal to 19,005,490 t/y, taking into consideration their annual production and their respective residue production in Greece. Accordingly, the theoretical annual potential of livestock manure, including the residues from animal husbandry in Greece (cattle, chicken, goats, pigs, sheep etc.) was estimated equal to 26,952,500 t/y. In this study, the possibility of energy production through anaerobic digestion was investigated. Taking into account the biodegradability of the residues, it was estimated that the total 45,957,990 t/y residues may produce 330,000 t/y fertilizer and 1.97 × 109 m3/y methane. Taking advantage of the energy content of biogas by co-generation of energy and heat, 4.9–7.9 ΤWh/y of electrical energy and 6.9–12.8 ΤWh/y of thermal energy could be produced. Given the annual electrical energy consumption in Greece, about 39 % of this energy need could be replaced by electrical energy produced from agricultural residues and livestock manure. Conclusively, crop residues and livestock manure may stand as an energy source with significant contribution to the Greek energy balance.

English

Crop production in Mt. Elgon region (Uganda) generates a significant amount of crop residues (CR) that have for a long time been considered as ‘trash’ or agricultural waste. This neglect is due, in part, to the absence of a clear institutional framework governing utilization of CR. This paper presents a case for understanding of institutions that govern practices of CR utilization. It adopts the Institutional Analysis and Development framework to trace the evolution of institutional mechanisms governing utilization of CR; review the role of current institutional arrangements in influencing CR utilization among farming households; and recommend options that bolster household actions towards the utilization of CR. A synthesis of colonial institutional frameworks including bylaws showed that farmers were encouraged to engage in several soil conservation practices. Strict enforcement of these laws weakened after independence and almost collapsed with successive regimes. There is still a lack of an appropriate institutional framework at local level to influence the utilization of CR in Mt. Elgon region. The paper argues that proper institutional frameworks that penalize improper land use and incentivize better land use practices; build the capacity of farmers through awareness raising programs; and encourage better technologies for CR handling and storage should be strengthened. Key words: Crop residues, policies, smallholder farmers, Mt. Elgon Uganda.

Net primary productivity and below-ground crop residue inputs for root crops: Potato (Solanum tuberosum L.) and sugar beet (Beta vulgaris L.)

Bolinder, M. A., Kätterer, T., Poeplau, C., Börjesson, G. and Parent, L. E. 2015. Net primary productivity and below-ground crop residue inputs for root crops: Potato (Solanum tuberosum L.) and sugar beet (Beta vulgaris L.). Can. J. Soil Sci. 95: 87–93. Root crops are significant in agro-ecosystems of temperate climates. However, the amounts of crop residues for these crop types are not well documented and they need to be accounted for in the modeling of soil organic carbon dynamics. Our objective was to review field measurements of root biomass left in the soil as crop residues at harvest for potato and sugar beet. We considered estimates for crop residue inputs as root biomass presented in the literature and some unpublished results. Our analysis showed that compared to, for example, cereals, the contribution of below-ground net primary productivity (NPP) to crop residues is at least two to three times lower for root crops. Indeed, the field measurements indicated that root biomass for topsoils only represents on average 25 to 30 g dry matter (DM) m−2 yr−1. Other estimates, albeit variable and region-specific, tended to be higher. We suggest relative plant DM allocation coefficients for agronomic yield (RP), above-ground biomass (RS) and root biomass (RR) components, expressed as a proportion of total NPP. These coefficients, representative for temperate climates (0.739:0.236:0.025 for potato and 0.626:0.357:0.017 for sugar beet), should be useful in the modeling of agro-ecosystems that include root crops.

Nitrogen and phosphorus fertilization with crop residue retention enhances crop productivity, soil organic carbon, and total soil nitrogen concentrations in sandy-loam soils in Ghana

Sustainable management practices are needed to enhance soil organic carbon (SOC) in degraded soils in semi-arid West Africa. We studied the effects of three amounts of nitrogen (N) (0, 60 and 120 kg N ha−1) and three amounts of phosphorus (P) fertilizer (0, 26 and 39 kg P ha−1) application over four seasons on maize residue production, residue C, N, and P concentrations, and their impacts on SOC, total soil nitrogen (TSN), and total soil phosphorus (TSP) in the 0–20 cm soil layer. Combined application of N and P fertilizers substantially increased maize grain yield on average by 294 % and biomass produced and returned to the soil by about 60–70 % compared with no fertilization. Annual C, N, and P inputs from crop residue were significantly higher with combined application of N and P fertilizer. The increased amount of crop residue and consequent increased residue C, N and P returned to the soil significantly increased SOC, TSN and TSP in the 0–20 cm soil layer after four seasons. There was a significant correlation between the amount of crop residues returned to the soil over four seasons and SOC (r = 0.82; P = 0.007), TSN (r = 0.75; P = 0.020) and TSP (r = 0.69; P = 0.039). We concluded from these experiments that returning crop residues, application of inorganic fertilizer improves SOC, TSN and TSP concentrations and enhances crop productivity. The farmers who traditionally remove crop residues for fodder and fuel will require demonstration of the relative benefits of residues return to soil for sustainable crop productivity.

Effects of straw mulch on growth and yield of durum wheat during transition to Conservation Agriculture in Mediterranean environment

In Mediterranean environment, the transition to Conservation Agriculture (CA) poses as major issue the scarce accumulation of residues on soil surface; covering the soil with additional straw mulch could be a proven strategy for soil and water conservation, especially where durum wheat is the main crop, until reaching a layer of adequate thickness, typical of the stabilized CA systems.Two field trials were carried out from 2010 to 2012 in a representative area of Southern Italy during the first two years of transition to CA. Durum wheat was grown under three increasing levels of straw added as soil mulching: 5.0tha−1 (100% mulch cover (100%MC)), 2.5tha−1 (50%MC) and 1.5tha−1 (30%MC), plus a CONTROL. The influence of such additional straw on soil water and nutrient availability, physiological traits, growth and yield of durum wheat was assessed, as well as the necessary amount of additional straw was estimated.Both years of study indicated that root-zone moisture contents, monitored at 5cm depth starting from the beginning of head emergence, were significantly improved by mulching, with the highest differences detected between 100%MC and CONTROL (36 and 41% higher in 2011 and 2012, respectively). 100%MC exhibited also the significant lowest concentration of nitrate-N (9mgL−1 on average), K, Ca and Mg in soil solution. Additional straw at higher rates improved crop physiology: leaf water content (LWC) was highest in 100%MC (48.3%) and lowest in CONTROL (38.2%); SPAD and NDVI values (chlorophyll content) were respectively increased by 25% and 22% in 100%MC and by 15% and 17% in 50%MC, with respect to CONTROL. Nitrogen Nutrition Index (NNI) at anthesis was highest in 100%MC (0.97 vs. 0.50 in CONTROL). Significant high correlations were found between yield components and water as well as NO3− availability in soil solution (number of grainsm−2 vs. NO3− in soil solution R2 0.89; number of grainsm−2 vs. soil water R2 0.96). Yield was significantly affected by crop dry weight and N status at anthesis (0.49kgm−2 in 100%MC vs. 0.27kgm−2 in CONTROL, averaged over years). Moreover, the plots with higher amount of additional straw (100%MC and 50%MC) promoted significantly the accumulation of nitrogen in grains (0.56mgNgrain−1 in 2011 and 0.51mgNgrain−1 in 2012 in 50%MC).Under our experimental conditions, 1.5tha−1 of straw added as mulching are enough to significantly produce higher yields, although to exert significant positive effects both on soil and on crop physiological indicators, 2.5tha−1 of wheat straw are necessary. However, increasing the amount of crop residues until 5tha−1, crop performances and soil characteristics continue to significantly improve.

Study on the supply capacity of crop residue as energy in rural areas of Heilongjiang province of China

Abstract Heilongjiang is the most northeastern province of China. The climate of Heilongjiang consists of very cold winters, leading to large energy demands for space heating by local residents. Rich food crop yields in Heilongjiang results in large amounts of crop residues. To fully accommodate rural energy demand and facilitate the effective utilization of crop residues, this study builds a mathematical model of supply capacity of crop residues as energy, then, based on the data from a field survey and literature review, calculates the local annual effective heat demands for living, the supply rates for effective heat of different crop residue utilization patterns, and the supply capacities of crop residues as energy in rural areas of Heilongjiang. Results show that the supply capacity of traditional direct burning of crop residues is less than 1, indicating that direct burning of crop residues cannot fully supply rural living heat demands. The supply capacity of densification is more than 1.6, indicating that introducing densification can not only achieve full supply for rural living heat demands, but also result in a large proportion of crop residues remaining for other uses. Because part of the crop residues is converted to products other than gas, dry distillation can only supply 55% of the rural living heat demands. Introducing efficient technologies of crop residue utilization for energy in rural areas of Heilongjiang can make the available amount of energy from crop residues larger than the amount of energy demand. This study found that the combination of densification and dry distillation of crop residues can be used as a high-efficiency centralized supplement of living heat, achieving multiple benefits such as use of alternatives to fossil fuel energy, economic development, environment protection, and improvement in quality of life.