Soil organic matter,greenhouse gases and net global warming potential of irrigated conventional,reduced-tillage and organic cropping systems

Reducing tillage intensity and diversifying crop rotations may improve the sustainability of irrigated cropping systems in semi-arid regions. The objective of this study was to compare the greenhouse gas (GHG) emissions, soil organic matter, and net global warming potential (net GWP) of a sugar beet (Beta vulgaris L.)-corn (Zea mays L,) rotation under conventional (CT) and reduced-tillage (RT) and a corn-dry bean (Phaseolus vulgaris L.) rotation under organic (OR) management during the third and fourth years of 4-year crop rotations. The gas and soil samples were collected during April 2011–March 2013, and were analyzed for carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) emissions, water-filled pore space (WFPS), soil nitrate (NO₃ ^?–N) and ammonium (NH₄ ⁺–N) concentrations, soil organic carbon (SOC) and total nitrogen (TN), and net global warming potential (net GWP). Soils under RT had 26% lower CO₂ emissions compared to 10.2 kg C ha^?1 day^?1 and 43% lower N₂O emissions compared to 17.5 g N ha^?1 day^?1 in CT during cropping season 2011, and no difference in CO₂ and N₂O emissions during cropping season 2012. The OR emitted 31% less N₂O, but 74% more CO₂ than CT during crop season 2011. The RT had 34% higher SOC content than CT (17.9 Mg ha^?1) while OR was comparable with CT. Net GWP was negative for RT and OR and positive for CT. The RT and OR can increase SOC sequestration, mitigate GWP and thereby support in the development of sustainable cropping systems in semiarid agroecosystems.     

Exploitation of allelopathy for weed control in annual and perennial cropping systems

A variety of crops, cultivars, and accessions have been evaluated over the past six years for superior capability to suppress weed growth. The most successful of these approaches has been to grow cover crops of rye (Secale cereale), wheat (Triticum aestivum), sorghum (Sorghum bicolor), or barley (Hordeum vulgare) to a height of 40–50 cm, desiccate the crops by contact herbicides or freezing, and allow their residues to remain on the soil surface. Often, up to 95% control of important agroecosystem weed species was obtained for a 30- to 60-day period following desiccation of the cover crop. The plant residues on the soil surface exhibit numerous physical and chemical attributes that contribute to weed suppression. Physical aspects include shading and reduced soil temperatures which were similarly achieved using poplar (Populus) excelsior as a control mulch. Chemical aspects apparently include direct release of toxins, as well as production of phytotoxic microbial products. Numerous chemicals appear to work in concert or in an additive or synergistic manner to reduce weed germination and growth.     

Management of soil organic matter in semiarid Africa for annual cropping systems

Ensuring sustainable agriculture in semiarid Africa requires the implementation of methods to balance nutrients and to conserve soil organic matter (SOM). There is an urgent need to improve the management of all types of SOM input. In this paper; the authors review a wide range of agricultural practices and discuss their advantages, limitations and feasibility. They distinguish ‘traditional systems’ such as traditional fallow, parkland and manuring from ‘improved systems’ such as ‘improved fallow’, forest fallow, alley cropping, cover crops and application of composted manure. Biomass production (BMP) for ‘improved systems’ is mainly linked: (i) for agroforestry, to the tree species used in forest fallow, to the synchronization of nutrient supply by the soil with the cereal demand in alley cropping, and generally to the efficiency of the root system and its development with the depth; (ii) for cover crops, BMP is mainly linked to the initial soil fertility and to the ecological zone: establishment and management of cover crops are not yet fully mastered under some conditions such as an annual rainfall below 800 mm and/or on very clayey soils; (iii) for manure, BMP is mainly linked to the improvement of fallow in order to ensure sufficient forage resources. Because semiarid Africa is mainly a livestock zone, the authors emphasise manure: constraints, quality indicators and tools used to encourage its production, are analysed. Thus it was concluded that the intensification of manure production and its rational use in semiarid African regions, threatened by drought and malnutrition, is very important: this cannot be separated from the production of plant biomass, whose possibilities have been examined above. This revised version was published online in June 2006 with corrections to the Cover Date.     

Trade-off between productivity enhancement and global warming potential of rice and wheat in India

Increased use of irrigation and nitrogen (N) in rice and wheat would increase productivity. It would also enhance the emission of greenhouse gases from soil causing global warming and climate change. This study quantified the trade-offs between increased production with N fertilizer and irrigation application and the global warming potential (GWP) in the major rice and wheat growing regions of India. The InfoCrop model was used to simulate yield and GWP of rice and wheat for five regions in the country for two climatic scenarios i.e., current (1990–1999) and future (2050), two irrigation practices i.e., supply-driven irrigation (SDI) and demand-driven irrigation (DDI), and 10 levels of N and organic manure. Rice and wheat productivity of India can be increased from their current productivity of 3.26 and 2.73 Mg ha⁻¹ to 5.66 and 6.15 Mg ha⁻¹, respectively with increased irrigation and N use. But this would increase the GWP by 27 and 40%, respectively. In spite of the increased GWP the carbon efficiency ratio (CER) would increase from the current values of 0.67 and 0.85 to 1.06 and 1.75 in rice and wheat, respectively. Thus there is a ‘win-win’ situation in terms of increased CER for increasing productivity. These situations need to be identified to harness the benefit with more rational management practices including efficient use of irrigation and N, the major drivers for yield and GWP.     

Nitrogen fixation and productivity of winter annual legume cover crops in Upper Midwest organic cropping systems

Nutrient Cycling in Agroecosystems - Legume cover crops can play a valuable role in maintaining and increasing soil quality and nitrogen availability, but are infrequently grown in the Upper...     

Nutrient recycling potential of Tephrosia candida in cropping systems of southeastern Nigeria

Improving fallow quality in cassava–fallow rotations in southeastern Nigeria through the use of leguminous cover crops has been shown to sustain the productivity of such systems. We studied the effects of age (1 or 2 years) of Tephrosia candida fallow on biomass and nutrient accumulation, on weed biomass and yield response of cassava/maize intercrop and on changes in soil chemical properties in a 3 yr field trial. Results were compared with those obtained in natural fallow. Total biomass and litter were three times higher in plots fallowed for 2 yr with Tephrosia candida than in those under natural fallow for the same period. Weed biomass was 205% lower in T. candida plots fallowed for 2 yr than in the natural fallow and was 174% smaller in T. candida plots fallow for 1 yr than in the natural fallow. Nutrient (nitrogen, phosphorus, calcium, magnesium and potassium) yields in leaves of T. candida fallow for 2 yr were on average 200–300% higher than in leaves of other fallows. The same trend was observed for cassava and maize yields. Soil chemical changes at soil depth 0 to 5 cm showed significant increases in N and C concentrations after 2 yr fallowing and a year of cropping, particularly in the planted fallow plots. Conversely, soil pH, available P and the exchangeable cations, especially Ca were lower, while Al was higher than the initial values, mainly in plots fallowed under T. candida, indicating a tendency of this fallow species to further exacerbate the soil acidification problem of the acid Ultisol at the study site in southeastern Nigeria.     

Greenhouse gas emissions from simulated beef and dairy livestock systems in the United States

Computer spreadsheets were developed to evaluate greenhouse gas (GHG) emissions from U.S. beef and dairy livestock systems from nine locations. Of the beef systems the cow-calf herd emitted the most and feedlot cattle the least methane (CH₄) and nitrous oxide (N₂O) per unit product. Carbon dioxide (CO₂) emissions per unit product were the least for the cow-calf and greatest for the feedlot scenarios. In the dairy systems approximately one-half of the total GHG CO₂ equivalents were from CH₄ and one-third from N₂O. Mitigation strategies, such as intensive grazing, reduced GHG emissions by approximately 10%. This revised version was published online in August 2006 with corrections to the Cover Date.     

Greenhouse gas emissions in an agroforestry system of the southeastern USA

Agroforestry systems may provide diverse ecosystem services and economic benefits that conventional agriculture cannot, e.g. potentially mitigating greenhouse gas emissions by enhancing nutrient cycling, since tree roots can capture nutrients not taken up by crops. However, greenhouse gas emission data from agroforestry systems are not available in the southeastern USA, thus limiting our ability to optimize agroforestry management strategies for the region. We hypothesized that tree-crop interactions could prevent excess N from being released to the atmosphere as nitrous oxide (N₂O). We determined N₂O and carbon dioxide (CO₂) emissions, soil temperature, water content, and surface-soil inorganic N in an 8-year-old agroforestry site at the Center for Environmental Farming Systems in Goldsboro, North Carolina, USA. The experimental design was a factorial arrangement of soil texture (loamy sand, sandy loam, and clay loam) and canopy cover (cropped alley, margin between crops and trees, and under Pinus palustris, Pinus taeda, and Quercus pagoda) with three replications. Sampling occurred 42 times within a year using static, vented chambers exposed to the soil for 1-h periods. Soil N₂O emission was lower under tree canopies than in cropped alleys, and margin areas were intermediate. Soil texture, water content, and inorganic N were key determinants of the magnitude of N₂O emission. Soil CO₂ emission was controlled by temperature and water content as expected, but surprisingly not by their interaction. Soil temperature was 1.8 ± 1.3 °C lower and soil water content was 0.043 ± 0.15 m³ m^?3 lower under tree canopy than in cropped alleys, which helped to reduce CO₂ emission under trees relative to that in cropped alleys. Our results provide a foundation for reducing greenhouse gas emissions in complex agricultural landscapes with varying soil texture by introducing timber production without abandoning agricultural operations.     

Carbon,nitrogen and phosphorus stoichiometric ratios under cotton cropping systems in Australian Vertisols: a meta-analysis of seven experiments

Enhancing storage of carbon (C) in agricultural soil has been proposed as a partial solution to offset the accelerated release of greenhouse gases associated with global warming. A net loss of soil C is common in most cotton (Gossypium hirsutum L.)-based farming systems in Australian Vertisols. Some authors have suggested that an “ideal” stoichiometric ratio C:N:P:S of 10,000:833:200:143 was required for sustained C sequestration. The objective of this study was to determine the C, N, and P stoichiometric ratios that were present under cotton cropping systems sown in some typical irrigated and dryland Vertisols of Eastern Australia. Measurements were made on archived soil samples from seven experiments conducted between 1993 and 2012. Soil C sequestration was mostly negative in many of these sites or at best neutral. The archived soils were analysed for total P by digestion, and total C and N by dry combustion. The results were grouped and analysed according to four rotation types (continuous cotton systems, and cotton fb. (followed by) cereal, cotton fb. legume and cotton fb. cereal and legume, and two water management practices (irrigated and dryland) using a mixed model approach for meta-analysis of multiple experiments. Although small differences in C:N:P ratios existed among rotation types, values were much lower with irrigation (30:3:1) than in the dryland sites (263:14:1) and the “ideal” ratio (50:4:1). Low nutrient availability may not be the cause of soil C losses under irrigation but it may be one factor that inhibits C sequestration under dryland conditions.     

Impact of organic residue management on nitrogen use efficiency in an annual rice cropping sequence of lowland Central Thailand

Field experiments were conducted in Central Thailand under a rice–fallow–rice cropping sequence during consecutive dry and wet seasons of 1998 to determine the impact of residue management on fertilizer nitrogen (N) use. Treatments consisted of a combination of broadcast urea (70 kg N ha^–1) with rice straw (C/N 67) and rice hull ash (C/N 76), which were incorporated into the puddled soil 1 week before transplanting at a rate of 5 Mg ha^–1. Nitrogen-15 balance data showed that the dry season rice recovered 10 to 20% of fertilizer N at maturity. Of the applied N, 27 to 36% remained in the soil. Loss of N (unaccounted for) from the soil–plant system ranged from 47 to 54% of applied N. The availability of the residue fertilizer N to a subsequent rice crop was only less than 3% of the initial applied N. During both season fallows NO₃-N remained the dominant form of mineral-N (NO₃+NH₄) in the aerobic soil. In the dry season grain yield response to N application was significant (P=0.05). Organic material sources did not significantly change grain yield and N accumulation in rice. In terms of grain yields and N uptake at maturity, there was no significant residual effect of fertilizer N on the subsequent rice crop. The combined use of organic residues with urea did not improve N use efficiency, reduced N losses nor produced higher yields compared to urea alone. These results suggested that mechanisms such as N loss through gaseous N emissions may account for the low fertilizer N use efficiency from this rice cropping system. Splitting fertilizer N application should be considered on the fertilizer N use from the organic residue amendment.     

Total and organic soil carbon in cropping systems of Nepal

The significance of soil organic matter (SOM) in sustaining agriculture has long been recognized. The rate of change depends on climate, cropping system, cropping practice, and soil moisture. A 3-yr on-farm study was conducted in two major agro-ecologies (hills with warm-temperate climate and plains with subtropical climate) of Nepal. The soils in warm-temperate climate are Lithic subgroups of Ustorthents with well-drained loamy texture, and in subtropical climate are Haplaquepts with imperfectly drained loamy texture. Farmers’ predominant cropping systems were selected from different cultivation length in addition to a reference sample collected from adjacent virgin forest. The objectives were to examine the effect of cultivation length and cropping system on total carbon, KMnO₄-oxidizable soil C, C storage, and C/N ratio in two climatic scenarios: warm-temperate and subtropical. A large difference in KMnO₄-oxidizable soil organic C was observed due to the effect of cultivation length and cropping system. However, TC remained similar during the 3-year study. The decrease in KMnO₄-oxidizable C due to cultivation was more in the surface layer (43–56%) than in the subsurface layer (20–30%). Total C in uncultivated, < 10-year cultivated, and > 50-year cultivated soil was 22, 13, and 10 g kg⁻¹ in warm-temperate climate and 10, 6, and 5 g kg⁻¹ in subtropical climate, respectively. During the 3-year study period in both climates, large changes in soil C were observed for KMnO₄-oxidizable C but not for TC, confirming our earlier work on the usefulness of the KMnO₄ oxidized fraction for detecting a relatively short-term increase or decrease in soil C pool. The TC storage in uncultivated, < 10-year cultivated, and > 50-year cultivated soil was 38, 25, and 19 Mg ha⁻¹ in warm-temperate climate and 22, 15, and 12 Mg ha⁻¹ in subtropical climate, respectively. The rice–wheat and maize–potato cropping systems were good in storing soil C of 30 and 20 Mg ha⁻¹ for 0–15-cm soil depth in warm-temperate climate. The rice–wheat cropping system was also good in storing soil C in subtropical climate (19 Mg ha⁻¹) compared with other cropping systems studied.     

Nutrient recycling and physical indicators of an alley cropping system in a sandy loam soil in the pre-Amazon region of Brazil

The sustainable management of soils has proved a key challenge for the smallholder agriculture in southeastern Amazonia, Brazil. We assessed the capacity of an alley cropping system to sustain corn productivity. The experiment included six treatments: Clitoria + Pigeon Pea; Leucaena + Pigeon Pea; Acacia + Pigeon Pea; Clitoria + Leucaena; Leucaena + Acacia and Control treatment (no legumes). We determined chemical and physical indicators of soil quality. Leucaena had the highest macronutrient concentrations (40.17 g N kg⁻¹), except for P. All legumes had high Ca (13.82–17.84 g kg⁻¹) and very low P (0.51–2.83 g kg⁻¹) and Mg (1.73–2.92 g kg⁻¹) concentrations. Acacia had the lowest N, P, K and Mg concentrations. Pre-planting soil analysis indicated that soil quality indicators were below the critical levels needed for a productive agricultural system, especially for phosphorus, sum of bases and base saturation. Physical indicators of quality, such as bulk density (1.40–1.30 Mg m⁻³), total porosity (0.46–0.50 m m⁻³) and soil aeration capacity (0.10–0.17 m m⁻³), were substantially improved as a result of the surface application of residues. There was a cumulative effect of residue application on corn crop productivity. Because of its capacity to recycle nutrients and improve soil quality over the period of 3 years, alley cropping in association with no-tillage, can be an efficient strategy for maintaining productivity in the low-fertility soils of the humid tropics.     

Long-term effect of nutrient management and cropping system on cotton yield and soil fertility in rainfed vertisols

The effect of different N, P and K combinations with and without FYM on cotton productivity and the changes in soil fertility of three rainfed cotton based cropping systems were analyzed through a field experiment, conducted for 11 yr. Monoculture of G. arboreum (Asiatic) cotton, out-yielded monoculture of G. hirsutum (upland) cotton in 9 out of 11 yr. except in years of heavy rainfall. G. hirsutum cotton in rotation with sorghum produced 8% more yield than monocultured G. hirsutum. Significant responses to N and P application were consistently observed, while the response to K was inconsistent. Substituting half the N dose with FYM, gave 162 kg/ha and 222 kg/ha more seed cotton at low (N60 P13 K25) and high (N90 P20 K38) doses respectively. Also substituting half the N dose with FYM built up soil organic C from 4.2 to 5.4 g/kg, and increased available P from 4.5 to 6.4 mg/kg. The variations in the performance of the cropping systems and the response to fertilizers could not be accounted for by total rainfall alone. However, there was significant positive correlation between cotton yield and post September rainfall. Multiple regression equations were fitted to estimate G. arboreum and G. hirsutum yields based on the monthly distribution of rainfall.     

Agronomic potential and seed composition of cuphea,an annual crop for lauric and capric seed oils

Cuphea is an herbaceous summer annual plant native to Mexico. The seed oil contains various medium-chain fatty acids which, depending on the species, account for 40 to more than 80% of the total fatty acids. Cuphea oil could be a substitute for conconut- and palm kernel oil because of the high lauric acid content, but also could serve as a natural source of capric acid, which presently comes mainly from petrochemicals. Agronomic research recently begun at Oregon State University is directed toward adaptation and yield improvement of Cuphea. Initial Oregon field experiments in 1983 indicated that Cuphea is well adapted to the Willamette Valley. The plant, however, is not yet adapted to current farm production technology. Slow emergence and seedling growth may be altered by breeding and selection. Seed indehiscence and indeterminate growth already have been altered through mutations. In recent experiments seed yield could be increased significantly by multiple harvests, which indicates that further gain could be expected through improved technology. Present yield potential of Cuphea is about 300 kg of oil per hectare.     

Effect of long-term application of organic amendment on C storage in relation to global warming potential and biological activities in tropical flooded soil planted to rice

The impact of long term organic amendments on the functional microbial activities, soil carbon (C) storage in relation to greenhouse gas (GHG) emission from rice field was investigated in a tropical Aeric Endoaquept. The treatments included unamended control, farmyard manure (FYM), green manure (GM) (Sesbania aculeata), FYM?+?GM and rice straw (RS)?+?GM combination. Our results suggest that the FYM?+?GM treatment has increased the global warming potential (GWP) by 110?% as well decreased the C efficiency ratio by 24?% in comparison to control. On the other hand, under RS?+?GM treatment the soil organic C and total C contents were significantly higher to the tune of 34 and 53?%, respectively. Our studies clearly reveal that the application of RS?+?GM at 1:1 [Nitrogen (N) basis] could probably be the best soil amendment to sequester the soil organic C. Such amendments may not only have practical application value but also lead to higher yield capacity and minimize emission of GHG under flooded tropical rice soil systems.     

Some physical characteristics and heavy metal analyses of cotton gin waste for potential use as an alternative fuel

The use of cotton gin waste as a fuel is an attractive solution to the problems of disposing of a surplus agricultural waste as well as supplementing energy resources. Because a qualified alternative fuel must meet both environmental emission standards and industrial fuel standards, the physical characteristics of cotton gin waste and its toxic element concentrations are important for its initial objective evaluation as a fuel. Constituent components, moisture contents, and ash contents of four separate parts of cotton gin waste were determined and evaluated, closely following the American Society for Testing and Materials (ASTM) test methods. The three most toxic heavy metals, arsenic (As), chromium (Cr), and lead (Pb), chosen for quantitative analyses were also determined by using an inductively coupled plasma atomic emission spectrometry and a microwave oven sample digestion method. This study revealed that the lint component is the leading candidate for fuel, which closely meets both environmental emission and industrial fuel standards.     

Adsorption and fixation of a reactive dye on cotton in non-aqueous systems

The dyeability of a reactive dye, CI Reactive Red 2, on cotton in non-aqueous media has been investigated using a reverse-micellar solution. Reverse micelles comprising Aerosol-OT/iso-octane were taken as a model for dyeing in non-aqueous systems. The reactive dye was satisfactorily solubilised in the interior of the reverse micelle. Exhaustion of the reactive dye on cotton from the reverse micellar solution was excellent even in the absence of a dyeing auxiliary. Effective fixation was achieved by the use of a separate reverse-micellar solution containing a suitable alkali. It has also been shown that fixation can be successfully achieved using an alternative thermal process without the need for alkali.     

Camouflage of cotton fabrics in visible and NIR region using three selected vat dyes

To provide camouflage in near infrared (NIR) region and imitate reflectance profile of greenish leaves, cotton fabrics were dyed with three selected vat dyes, namely C.I. Vat Blue 6, C.I. Vat Yellow 2, and C.I. Vat Red 13. Reflectance curves of two types of fresh greenish leaves were measured as standard reference. Transmittance curve of vat dyes in acetone solution indicated that selected vat dyes have suitable structure to provide camouflage in NIR region. According to reflectance profiles, reflectance curve of Vat Blue 6 has more similarity with that of green leaf at the concentration of 0.85% owf (on weight of fiber) and 1.2% owf in comparison with those of C.I. Vat Yellow 2 and C.I. Vat Red 13. Cotton fabrics were dyed with different mixtures of the dyes to obtain a standard shade to reach camouflage in visible range. Chromatic values of dyed fabrics were measured (CIE1976 L*, a*, and b*) and two standard shades of the 1948 US army pattern, NATO and forest green, were obtained on cotton fabrics with ΔE_CMC < 2. Reflectance profiles of these two shades were located between the reflectance of green leaves. So, two vat dyes were introduced to camouflage dyes group, C.I. Vat Blue 6 and C.I. Vat Red 13, and used to achieve NATO green and forest green shades for first time. All dyed samples showed good fastness properties. The effect of washing and light exposure on camouflage properties of fabrics in visible and NIR region was inconsiderable. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 200–207, 2014     

桂中双季稻区磷肥用量对水稻生长与产量的影响

为探讨桂中双季稻区磷肥施用效应,2009年在广西进行了不同施磷水平对该地区早稻与晚稻的肥效试验。结果表明,与不施磷（P0）相比,早稻施磷处理产量平均提高9．83％,晚稻产量平均提高16．03％,而且当施P2O5量≤525kg／hm^2时,水稻产量随着施磷水平的增加而提高。可见,在桂中双季稻区适当增施磷肥是保证水稻高产稳产的主要措施之一。