• Authors:
    • Tyler, D. D.
    • Keyser, P. D.
    • Allen, F. L.
    • Reed, D. L.
    • Taylor, A. M.
    • Ashworth, A. J.
  • Source: JOURNAL OF CLEANER PRODUCTION
  • Volume: 87
  • Year: 2015
  • Summary: As the use of second-generation biofuel crops increases, so do questions about sustainability, particularly their potential to affect fossil energy consumption and greenhouse gas emissions. This study used a life-. cycle approach to compare environmental impacts associated with three switchgrass (Panicum virgatum L) production scenarios: i) regional production from a pool of Tennessee farmers based on in-field inputs and biomass yield; ii) varying nitrogen (N)-input levels from a replicated field study for 8-yrs i.e., a 100% and 9% decrease, and an 81% and 172% increase from 'baseline levels' of N inputs used under objective i; and, iii) a legume-intercrop system compared to baseline levels in order to determine effects of displacing synthetic-N with legumes. When compared across all agricultural inputs, nitrogen fertilizer production and breakdown resulted in the greatest environmental impacts. Although fertilization increased lignocellulosic yields, a 100% reduction in N-inputs from baseline levels reduced the formation of carbon, methane, and nitrous oxides per unit of production, (or dry tonne of biomass over 10-yrs) compared to a 172% increase. Switchgrass yield response indicated a 'less is more' scenario, as inputs beyond the current recommended input level (67 kg N ha(-1)) are not environmentally remunerating. During switchgrass biomass production, inputs with lesser impacts included phosphorus, herbicides, pesticides, and diesel fuel. Legume-intercropping reduced greenhouse gas emissions and groundwater acidification (5% and 27% reduction in global warming potential and formation of acidifying species, respectively) compared with the 67 kg N ha irate. Although N-fertilizers impact environmental sustainability of regional switchgrass feedstock production, environmental consequences can be reduced under proper N-management i.e., <= 67 kg N ha(-1) or legume intercropping. However, given that the aim of second-generation feedstocks is to reduce the current reliance on fossil fuels, their production still requires fossil energy-based inputs. Consequently, greenhouse gas reductions and the extent of cleaner feedstock production during the agricultural biofuel supply chain is contingent upon input management and optimizing synthetic fertilizer usage. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.
  • Authors:
    • Riseman, A.
    • Chapagain, T.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 1
  • Year: 2015
  • Summary: Enhancing soil organic carbon (SOC), nitrogen (N) and water use efficiency (WUE) are significant challenges in intensive wheat production. An intercropping system combining wheat and grain legumes may help maintain SOC, soil mineral N and WUE while also providing an opportunity to sequester carbon (C) in low input organic systems. We grew wheat (Triticum aestivum cv. 'Scarlet') as a monoculture and intercropped with either common bean (Phaseolus vulgaris cv. 'Red Kidney', or cv. 'Black Turtle'), or fava bean (Vicia faba cv. 'Bell') in rows of 1:1, 2 wheat: 1 bean or broadcast arrangement without fertilizers for 2 years to assess the effects of genotype and spatial arrangement on biological nitrogen fixation and seasonal transfer, WUE, gross ecosystem photosynthesis (GEP), and net ecosystem productivity (NEP). Stable isotope methods (C-13 and N-15 natural abundance) were used to quantify C and N within the plant and soil system. Field CO2 exchange measurements used a dynamic closed transparent chamber connected to a portable CO2 analyzer. Intercropped plots had higher percent N derived from symbiotic N-2 fixation, and increased C and N accumulation compared to monocultured wheat. The fava bean cv. Bell intercrops showed increased nodulation (60-80 % more nodules) and percent N derived from symbiotic N-2 fixation (10-12 % higher) compared to common beans resulting in the fixation of 74 kg N ha(-1) biologically from the 1:1 arrangement. The highest rate of N-transfer (13 %) was observed in the wheat-fava bean cv. Bell combination when planted in the 1:1 arrangement. All intercrops accumulated more N in shoot biomass compared to monoculture wheat with wheat-fava bean cv. Bell (1:1 arrangement) accumulating the highest N (34 kg N ha(-1), i.e., 176 % higher) and C (214 g C m(-2) year(-1), i.e., 26 % higher). All plots fixed the most CO2 (i.e., greatest GEP) during mid-growth stage (50 days after seeding i.e., prior to flowering) however, wheat-fava bean cv. Bell in the 1:1 arrangement displayed the greatest NEP sequestering C at the seasonal daytime average rate of 208 mg C m(-2) h(-1) (i.e., 7 % higher than wheat monoculture plots). Intrinsic WUE of wheat, as indicated by delta C-13, was also improved when grown with fava bean cv. Bell or common bean cv. Red Kidney. This study demonstrated that intercropping wheat and fava bean is an effective strategy to achieve greater nitrogen fixation and transfer to the wheat counterparts, higher WUE, and ecosystem productivity than wheat monocultures in areas with low soil N and C. Furthermore, the wheat-fava bean cv. Bell (1:1 arrangement) was more productive than either the 2:1 or mixed planting arrangements.
  • Authors:
    • Stoddard, F. L.
    • Simojoki, A.
    • Makela, P.
    • Jaakkola, S.
    • Santanen, A.
    • Saikkonen, L.
    • Epie, K. E.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 2
  • Year: 2015
  • Summary: Bioenergy cropping, like all agricultural practices, may lead to the release of greenhouse gases. This study was aimed at determining biomass and energy yields of reed canary grass (RCG) (Phalaris arundinacea), galega (Galega orientalis) and a mixture of these, and to relate these to fluxes of nitrous oxide (N2O), a potent greenhouse gas, emitted from the soils. Plots including a bare fallow as control were established in 2008. Gases emitted from the soil surface were collected in closed chambers from May 2011 to May 2013, except during periods of snow cover, and analysed by gas chromatography. Seasonal and annual cumulative emissions of N2O and CO2 equivalents per unit energy yield were calculated. Soil moisture content, nitrate (NO3 (-))-N and ammonium (NH4 (+))-N were also determined. Both species composition and crop yields affected energy yields and N2O emission from the soil. The annual cumulative emissions from mixture were marginally lower than those from fertilized RCG soils. Fertilized RCG produced twice as much biomass and correspondingly higher nitrogen and energy yields, so its low emission of N2O per Mg of dry matter was not significantly different from that of the mixtures. Cropping an RCG-galega mixture for biofuel may replace N fertilizer input since it resulted in lowering N2O fluxes, but requires management to maintain grass as the major component in order to minimize N2O emissions. In a time of climate change, low-input bioenergy crops may be a suitable strategy for land left uncropped after ploughing for one season or longer.
  • Authors:
    • van der Werf, W
    • Zhang, F. S.
    • Six, J.
    • Cong, W. F.
    • Hoffland, E.
    • Li, L.
    • Sun, J. H.
    • Bao, X. G.
  • Source: GLOBAL CHANGE BIOLOGY
  • Volume: 21
  • Issue: 4
  • Year: 2015
  • Summary: Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greater input of root litter. Here, we demonstrate a divergence in soil organic carbon (C) and nitrogen (N) content over 7 years in a field experiment that compared rotational strip intercrop systems and ordinary crop rotations. Soil organic C content in the top 20 cm was 4%1% greater in intercrops than in sole crops, indicating a difference in C sequestration rate between intercrop and sole crop systems of 18486 kg C ha -1 yr -1. Soil organic N content in the top 20 cm was 11%1% greater in intercrops than in sole crops, indicating a difference in N sequestration rate between intercrop and sole crop systems of 4510 kg N ha -1 yr -1. Total root biomass in intercrops was on average 23% greater than the average root biomass in sole crops, providing a possible mechanism for the observed divergence in soil C sequestration between sole crop and intercrop systems. A lowering of the soil delta 15N signature suggested that increased biological N fixation and/or reduced gaseous N losses contributed to the increases in soil N in intercrop rotations with faba bean. Increases in soil N in wheat/maize intercrop pointed to contributions from a broader suite of mechanisms for N retention, e.g., complementary N uptake strategies of the intercropped plant species. Our results indicate that soil C sequestration potential of strip intercropping is similar in magnitude to that of currently recommended management practises to conserve organic matter in soil. Intercropping can contribute to multiple agroecosystem services by increased yield, better soil quality and soil C sequestration.
  • Authors:
    • Gan, Y. T.
    • Cui, H. Y.
    • Yin, W.
    • Yu, A. Z.
    • Chai, Q.
    • Hu, F. L.
  • Source: AGRONOMY FOR SUSTAINABLE DEVELOPMENT
  • Volume: 35
  • Issue: 2
  • Year: 2015
  • Summary: Intercropping is used to increase grain production in many areas of the world. However, this increasing crop yield costs large amounts of water used by intercropped plants. In addition, intercropping usually requires higher inputs that induce greenhouse gas emissions. Actually, it is unknown whether intercropping can be effective in water-limited arid areas. Here, we measured crop yield, water consumption, soil respiration, and carbon emissions of wheat-maize intercropping under different tillage and crop residue management options. A field experiment was conducted at Wuwei in northwest China in 2011 and 2012. Our results show that wheat-maize intercropping increased grain yield by 61 % in 2011 and 63 % in 2012 compared with the average yield of monoculture crops. The intercropping under reduced tillage with stubble mulching yielded 15.9 t ha(-1) in 2011 and 15.5 t ha(-1) in 2012, an increase of 7.8 % in 2011 and 8.1 % in 2012, compared to conventional tillage. Wheat-maize intercropping had carbon emission of 2,400 kg C ha(-1) during the growing season, about 7 % less than monoculture maize, of 2,580 kg C ha(-1). Reduced tillage decreased C emission over conventional tillage by 6.7 % for the intercropping, 5.9 % for monoculture maize, and 7.1 % for monoculture wheat. Compared to monoculture maize, wheat-maize intercropping used more water but emitted 3.4 kg C per hectare per millimeter of water used, which was 23 % lower than monoculture maize. Overall, our findings show that maize-wheat intercropping with reduced tillage coupled with stubble mulching can be used to increase grain production while effectively lower carbon emissions in arid areas.
  • Authors:
    • Sucre, E. B.
    • Strahm, B. D.
    • Seiler, J. R.
    • Shrestha, P.
    • Leggett, Z. H.
  • Source: Conference: 17th Biennial Southern Silvicultural Research Conference, Shreveport, Louisiana, USA, 5-7 March 2013. General Technical Report - Southern Research Station, USDA Forest Service Issue: SRS-203
  • Issue: SRS-203
  • Year: 2015
  • Authors:
    • Sheaffer, C. C.
    • Fernandez, A. L.
    • Wyse, D. L.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Field pea ( Pisum sativum L.) and lentil ( Lens culinaris Medik.) have potential as grain-producing legumes in organic rotations, but their yield is limited by weed competition. Intercropping can control weeds and increase total grain productivity per land area compared to sole cropping. A field experiment was conducted to investigate the effect of intercropping on field pea and lentil yields. Intercrop treatments were spring wheat ( Triticum aestivum L.), oat ( Avena sativa L.), and radish ( Raphanus sativus L.), which were harvested for grain; and winter rye ( Secale cereale L.) and rapid-cycling brassica ( Brassica campestris L.), which were not harvested. Intercropped lentil yields and total (lentil plus intercrop) yields were lower than or equal to weeded and unweeded sole cropped lentils in 5 of 6 site-years. Intercropped pea yields and total (pea plus intercrop) yields were lower than or equal to weeded and unweeded sole cropped pea in all site-years. Unharvested intercrops showed variable effectiveness at suppressing weeds. In lentil, winter rye intercropping reduced weed biomass compared to the unweeded control in 4 site-years, and rapid-cycling brassica reduced weed biomass in 2 site-years. In pea, winter rye, and rapid-cycling brassica treatments reduced weed biomass in all site-years. However, reductions in weed biomass were not associated with increases in grain yield. Estimated net returns to intercropping were variable, but generally similar for sole crops and intercrops on average. We did not observe consistent agronomic or economic advantages to the use of intercrops with field pea and lentil in the Minnesota environments studied.
  • Authors:
    • Franco,J. G.
    • King,S. R.
    • Masabni,J. G.
    • Volder,A.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 203
  • Year: 2015
  • Summary: In natural ecosystems, plant communities composed of functionally diverse species produce more biomass overall than less diverse communities. This increased biomass production is thought to occur due to complementary use of resources such as nutrients and water, and facilitation during sub-optimal environmental conditions. Using the same concept in a crop setting may lead to increased yield (overyielding) in diverse cropping systems when compared to monocultures. Different combinations of peanut, watermelon, okra, cowpea, and pepper planted alone or in various intercropping combinations were investigated over two growing seasons in a low-input system in the peak of summer heat in Texas. Each species was selected to perform a specific function within the system. Results from land equivalent ratio (LER) indicate that the within-row combination with peanut, watermelon and okra ( Wpwo) and peanut, watermelon, okra and cowpea ( Wpwoc) consistently overyielded in 2011 and 2012. LER values were 1.17 each for Wpwo and Wpwoc in 2011 and 1.17 and 1.20 in 2012, respectively. In 2011, watermelon was the dominant crop and was up-regulated in all intercropping combinations while all other component crops were down-regulated. Watermelon per plant production was significantly higher in the combination containing all species ( Wall) when compared to its monoculture, 5.50 and 2.09 kg fruit plant -1, respectively. In 2012, okra was the dominant crop and was up-regulated in all intercropping combinations while watermelon, cowpea, and pepper were down-regulated. Okra per plant production was significantly higher in Wpwoc and Wall than in monoculture, 2.28, 2.46, and 1.13 kg fruit plant -1, respectively. These findings suggest that three and four species intercropping combinations, whereby each crop is selected to perform a specific function within the system, may provide small-scale sustainably-minded producers a model system that can be utilized in suboptimal conditions and allow them to reduce inputs while increasing overall yields.
  • Authors:
    • Holland,R. A.
    • Eigenbrod,F.
    • Muggeridge,A.
    • Brown,G.
    • Clarke,D.
    • Taylor,G.
  • Source: Renewable and Sustainable Energy Reviews
  • Volume: 46
  • Year: 2015
  • Summary: The production of bioenergy from second generation (2G) feedstocks is being encouraged by legislation targeted at addressing a number of controversial issues including carbon emissions driven by land-use change and competition for crops used in food production. Here, we synthesise the implications of 2G feedstock production for a range of key ecosystem services beyond climate regulation. We consider feedstocks typical of temperate systems (Miscanthus; short-rotation coppice, short rotation forestry) and transitions from areas of forest, marginal land and first generation (1G) feedstock production. For transitions from 1G feedstocks, studies suggest significant benefits may arise for a number of ecosystem services, including hazard regulation, disease and pest control, water and soil quality. Although less evidence is available, the conversion of marginal land to 2G production will likely deliver benefits for some services while remaining broadly neutral for others. Conversion of forest to 2G production will likely reduce the provision of a range of services due to increased disturbance associated with shortening of the management cycle. Most importantly, further research is needed to broaden, and deepen, our understanding of the implications of transitions to 2G feedstocks on ecosystem services, providing empirical evidence for policy development, particularly for commercial deployment where landscape scale effects may emerge. A programme of research that mixes both the natural and social sciences based on an ecosystem service framework, and occurs concurrently with large scale commercial deployment of 2G feedstocks, would address this gap, providing evidence on the effectiveness of policies to promote production of 2G feedstocks on a wide range of ecosystem services. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Miao,Shujie
    • Qiao,Yunfa
    • Zhang,Futao
  • Source: Polish Journal of Environmental Science
  • Volume: 24
  • Issue: 3
  • Year: 2015
  • Summary: In converting cropland to grassland and forest, more carbon is sequestered in grassland soil and forest biomass, but the mitigation of global warming potential (GWP) is not clear. In this study, we use the lon-gterm conversion from cropland to grassland (28 y) and forest (14 y) to comprehensively assess the impact on GWP of soil carbon (C), nitrogen (N), CO2 and N2O emissions. The results showed that compared to the original cropland, conversion to grassland increased soil C content by 51.1%, soil N content by 28.4%, soil C stock (SCS) by four times, CO2 emission by 17%, and N2O emission by 40%; soil N stock (SNS) decreased by half. The corresponding values after afforestation were 7.2%, 5.2%, three times, 3%, -80%, and half, respectively. Overall GWP in the cropland system was calculated using the fuel used for farming production, the change in soil C, and N2O emissions. Due to large C sequestration, the GWP of conversion to grassland (-1667 kg CO2-C equivalent ha(-1).y(-1)) and forest (-324 kg CO2-C equivalent ha(-1).y(-1)) were significantly lower than the cropland system (755 kg CO2-C equivalent ha(-1).y(-1)). The relationship between GWP and greenhouse gas, between GWP and the change of total C and N, suggest that in rain-fed agricultural systems in northeast China, the conversion from cropland to grassland and forest can mitigate GWP through changing CO2 and N2O emissions.