• Authors:
    • Ashworth,A. J.
    • West,C. P.
    • Allen,F. L.
    • Keyser,P. D.
    • Weiss,S. A.
    • Tyler,D. D.
    • Taylor,A. M.
    • Warwick,K. L.
    • Beamer,K. P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Biological N 2 fixation (BNF) via legume intercrops can provide an alternative to inorganic N fertilizer and thereby minimize the economic and environmental costs of bioenergy feedstock and forage production. The objectives of this study were to (i) verify switchgrass ( Panicum virgatum L.) as a non-N 2-fixing reference plant for distinguishing between soil- and atmosphere-derived N; (ii) determine BNF levels via the 15N enrichment method for one cool-season legume (red clover [ Trifolium pratense L.]) and three warm-season legumes ([partridge pea] [ Chamaecrista fasciculate Michx.], sunn hemp [ Crotalaria juncea L.], and pigeonpea [ Cajanus cajan (L.) Millsp.]) when intercropped into switchgrass and a near relative, guineagrass ( Panicum maximum L.); and (iii) evaluate the validity of the N-difference method by comparing it against the 15N enrichment technique in humid temperate and semiarid tropical climates. The results revealed little difference in the N assimilation rates of legume and non-N 2-fixing reference plants, suggesting that switchgrass is an appropriate reference species. Annual fixation for red clover was greatest, followed by partridge pea, and lastly sunn hemp in temperate systems (87, 84, and 35 kg ha -1, respectively), all of which tended to supply greater amounts of N in subsequent seasons. Considerably greater BNF occurred in tropical intercrop systems (exceeding 240 kg ha -1). Consequently, the BNF of selected legumes approximates or exceeds recommended N fertilizer rates (67 kg N ha -1) in both humid temperate and semiarid tropical pasture and feedstock systems. The N-difference method did not provide estimates for BNF that were comparable to 15N-enrichment-derived values ( P>0.05).
  • Authors:
    • Chen, D.
    • Weng, B.
    • Zhang, J.
    • Zheng, X.
    • Hu, X.
    • Zhang, Y.
    • Li, S.
    • Ding, H.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 103
  • Issue: 3
  • Year: 2015
  • Summary: To investigate the fate of urea nitrogen (N) applied to vegetable fields, three N rates, N0 (0 kg N/ha), N1(225 or 240 kg N/ha) and N2 (450 or 480 kg N/ha) were applied to a rotation system. Nitrogen fertilizer recovery (NFR), N residue in soil, and N losses were measured in situ. Higher N application rates resulted in lower NFR, and increased N residues in soil and losses. The NFR, Chinese cabbage, and eggplant were different in the N1 and N2 groups (P < 0.01). The ratios of N fertilizer residue at 0-60 cm deep ranged from 30.2 to 41.1 % (N1), and 33.1 to 57.7 % (N2). The N loss ratios were only 6.6 % (N1) and 11.9 % (N2), because of the lower precipitation rates and temperatures characteristic of its growing season; meanwhile, N losses were 31.1 and 37.4 % in cayenne pepper, and 24.1 and 29.2 % in eggplants in the N1 and N2 treatments, respectively. The main pathways of N loss were leaching, followed by gaseous losses; these were major pathways of N loss in seasons with lower precipitation rates. NH3 volatilization was correlated with soil temperature (P < 0.01), and N2O emissions were correlated with soil moisture in the N1 treatment and with soil NH4 (+)-N concentration in the N2 treatment (P < 0.01). Denitrification rates were correlated with soil moisture in the N0 and N1 treatments, and with NO3 (-)-N content in the N2 treatment (P < 0.01). Finally, loss due to runoff was correlated with precipitation (P < 0.01).
  • Authors:
    • Larsen, E.
    • Grossman, J.
    • Hoyt, G.
    • Line, D.
    • Osmond, D.
    • Edgell, J.
  • Source: Journal of Environmental Quality Abstract - Surface Water Quality
  • Volume: 44
  • Issue: 6
  • Year: 2015
  • Summary: Organic agricultural systems are often assumed to be more sustainable than conventional farming, yet there has been little work comparing surface water quality from organic and conventional production, especially under the same cropping sequence. Our objective was to compare nutrient and sediment losses, as well as sweet corn ( Zea mays L. var. saccharata) yield, from organic and conventional production with conventional and conservation tillage. The experiment was located in the Appalachian Mountains of North Carolina. Four treatments, replicated four times, had been in place for over 18 yr and consisted of conventional tillage (chisel plow and disk) with conventional production (CT/Conven), conservation no-till with conventional production (NT/Conven), conventional tillage with organic production (CT/Org), and conservation no-till with organic production (NT/Org). Water quality (surface flow volume; nitrogen, phosphorus, and sediment concentrations) and sweet corn yield data were collected in 2011 and 2012. Sediment and sediment-attached nutrient losses were influenced by tillage and cropping system in 2011, due to higher rainfall, and tillage in 2012. Soluble nutrients were affected by the nutrient source and rate, which are a function of the cropping system. Sweet corn marketable yields were greater in conventional systems due to high weed competition and reduced total nitrogen availability in organic treatments. When comparing treatment efficiency (yield kg ha -1/nutrient loss kg ha -1), the NT/Conven treatment had the greatest sweet corn yield per unit of nutrient and sediment loss. Other treatment ratios were similar to each other; thus, it appears the most sustainably productive treatment was NT/Conven.
  • Authors:
    • Mondani, F.
    • Khoramivafa, M.
    • Yousefi, M.
  • Source: ATMOSPHERIC ENVIRONMENT
  • Volume: 92
  • Year: 2014
  • Summary: The main aim of this study was to determine and discuss the aggregate of energy use and greenhouse gas emission (CO 2, N 2O, and CH 4) for sugar beet agroecosystems in western of Iran. For this propose data was collected by using questionnaires and face to face interview with 50 farmers. Results showed that total inputs and output energy were 49517.2 and 1095360.0 MJ ha -1, respectively. Energy use efficiency was 22.12. Total CO 2, N 2O and CH 4 emissions due to chemical inputs were 2668.35, 22.92 and 3.49 kg, respectively. In sugar beet farms total global warming potential (GWPs) was 9847.77 kg CO 2eq ha -1. In terms of CO 2 equivalents, 27% of the GWP s come from CO 2, 72% from N 2O, and 1% from CH 4. In this research input and output carbon were 29340.0 and 2678.6 kg C ha -1, respectively. Hence, carbon efficiency ratio was 10.95.
  • Authors:
    • Radicetti, E.
    • Di Felice, V.
    • Mancinelli, R.
    • Campiglia, E.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 139
  • Year: 2014
  • Summary: There is a lack of information regarding the long-term residual effects of winter cover crops on the following cash crops. Two 2-year field experiments (from 2009 to 2012) were carried out in the Mediterranean environment of Central Italy in a Typic Xerofluvent soil. Endive (Cichorium endivia L.) and savoy cabbage (Brassica oleracea var. sabauda) were grown following a winter cover crop-pepper (Capsicum annum L.) sequence. We hypothesized that some cover crops and their residue management can have a long-term effect on the availability of soil nitrogen. The objectives were to quantify the: (i) nitrogen remaining in the soil and in the residues of cover crops after pepper cultivation; (ii) endive and savoy cabbage response due to the residual effect of cover crop residues, and (iii) mass of inorganic nitrogen required for obtaining a similar effect to that obtained with the residues of cover crops. The treatments consisted in three cover crop species [hairy vetch (Vicia villosa Roth.), oat (Avena sativa L.) and oilseed rape (Brassica napus L.)], three managements of the aboveground biomass of cover crops [incorporated into the soil 30cm depth (conventional tillage, CT), incorporated into the soil 10cm depth (minimum tillage, MT), left on the soil surface in mulch strips (no-tillage, NT)] plus a control without cover (no cover) fertilized with three levels of nitrogen (none, medium, high). At transplant of vegetables, the nitrogen in the cover crop residues ranged from 60kgha-1 in hairy vetch NT to 9kgha-1 in oilseed rape CT, while the soil inorganic nitrogen (NO3-N+NH4-N) was about twice in hairy vetch (20.9+7.4mgkg-1 dry soil, respectively) compared with oat and 1.5 times compared with oilseed rape. The marketable yield of endive and savoy cabbage was approximately tripled in hairy vetch compared to oat, oilseed rape and the unfertilized control (20.4 and 18.6 vs. 6.7 and 5.2tha-1 of FM, respectively). The endive and savoy cabbage yield was higher in NT and MT than in CT hairy vetch and similar to no cover fertilized with 50 and 75kgha-1 of N, respectively. Results confirm the hypothesis that some cover crops, such as hairy vetch, can have a long-term effect on the availability of soil nitrogen which exceeds the cultivation period of the following summer vegetable crop and can be profitably used by a second cash crop transplanted in close sequence. © 2014 Elsevier B.V.
  • Authors:
    • Cao, A. C.
    • Guo, M. X.
    • Wang, R Q.
    • Zhang, C L.
    • Liu, P. F.
    • Ma, T.T.
    • Yan, D. D.
    • Wang, D.
    • Mao, L. G.
    • Wang, Q. X.
  • Source: JOURNAL OF ENVIRONMENTAL QUALITY
  • Volume: 43
  • Issue: 5
  • Year: 2014
  • Summary: Soil fumigation is an important treatment in the production chain of fruit and vegetable crops, but fumigant emissions contribute to air pollution. Biochar as a soil amendment has shown the potential to reduce organic pollutants, including pesticides, in soils through adsorption and other physicochemical reactions. A laboratory column study was performed to determine the effects of soil applications of biochar for reducing emissions of the fumigant 1,3-dichloropropene (1,3-D). The experimental treatments comprised of unamended and amended with biochar at doses of 0, 0.5, 1, 2, and 5% (w/w) in the top 5 cm soil layer. The unamended treatment resulted in the highest emission peak flux at 48 to 66 g m -2 s -1. Among the biochar amendment treatments, the highest peak flux (0.83 g m -2 s -1) was found in the biochar 0.5% treatment. The total emission loss was 35.7 to 40.2% of applied for the unamended treatment and 99.8% and showed total 1,3-D emission loss by >92% compared with that without biochar. The amendment of surface soil with biochar shows a great potential for reducing fumigant emissions.
  • Authors:
    • Yoshihara, T.
    • Goto, F.
    • Shoji, K.
    • Kitazaki, K.
    • Johkan, M.
    • Hashida, S.
  • Source: Plant and Soil
  • Volume: 374
  • Issue: 1-2
  • Year: 2014
  • Summary: Nitrous oxide (N2O) is a strong greenhouse effective gas (GHG); the primary human source of N2O is agricultural activities. Excessive nitrogen (N) fertilization of agricultural land is now widely recognized as a major contributor. In soil, the microbial processes of nitrification and denitrification are the principal sources of N2O. However, it remains poorly understood how conventional hydroponics influences GHG emission. Here, we compared GHG fluxes from soil and rockwool used for hydroponics under identical nutrient conditions. Tomato plants (Solanum lycopersicum, momotaro) were grown in soil or by hydroponics using rockwool. In situ emissions of CH4, CO2, and N2O, and the abundance of genes involved in nitrification and denitrification were measured during cultivation. Hydroponics with rockwool mitigated CO2 emission by decreasing the microbial quantity in the rhizosphere. Dilution of the nutrient solution significantly decreased N2O emission from rockwool. Although proliferation of nitrifiers or denitrifiers in the rhizosphere did not induce N2O emission, reuse or long-term use of rockwool induced a 3.8-fold increase in N2O emission. Our data suggest that hydroponics has a lower environmental impact and that adequate fertilizer application, rather than bacterial control, governs N2O fluxes in hydroponic cultivation using rockwool.
  • Authors:
    • Wuta, M.
    • Nyamangara, J.
    • Masaka, J.
  • Source: Archives of Agronomy and Soil Science
  • Volume: 60
  • Issue: 10
  • Year: 2014
  • Summary: Agricultural soils are a primary source of anthropogenic trace gas emissions, and the subtropics contribute greatly, particularly since 51% of world soils are in these climate zones. A field experiment was carried out in an ephemeral wetland in central Zimbabwe in order to determine the effect of cattle manure (1.36%N) and mineral N fertilizer (ammonium nitrate, 34.5%N) application on N2O fluxes from soil. Combined applications of 0kgN fertilizer+0Mg cattle manure ha(-1) (control), 100kgN fertilizer+15Mg manure ha(-1) and 200kgN fertilizer+30Mg manure ha(-1) constituted the three treatments arranged in a randomized complete block design with four replications. Tomato and rape crops were grown in rotation over a period of two seasons. Emissions of N2O were sampled using the static chamber technique. Increasing N fertilizer and manure application rates from low to high rates increased the N2O fluxes by 37-106%. When low and high rates were applied to the tomato and rape crops, 0.51%, 0.40%, and 0.93%, 0.64% of applied N was lost as N2O, respectively. This implies that rape production has a greater N2O emitting potential than the production of tomatoes in wetlands.
  • Authors:
    • Mukherjee, A.
    • Lal, R.
  • Source: Soil Research
  • Volume: 52
  • Issue: 3
  • Year: 2014
  • Summary: Any strategy towards widespread adoption of biochar as a soil amendment is constrained by the scarcity of field-scale data on crop response, soil quality and environmental footprint. Impacts of biochar as a soil amendment over a short period based on laboratory and greenhouse studies are often inconclusive and contradictory. Yet biochar is widely advocated as a promising tool to improve soil quality, enhance C sequestration, and increase agronomic yield. While substantial reviews exist on positive aspects of biochar research, almost no review to date has compiled negative aspects of it. Although biochar science is advancing, available data indicate several areas of uncertainty. This article reviews a range of negative impacts of biochar on soil quality, crop yield, and associated financial risk. This review is important because advances in biochar research demand identification of the risks (if any) of using biochar as a soil amendment before any large-scale field application is recommended. It is the first attempt to acknowledge such issues with biochar application in soil. Thus, the aims of this review are to assess the uncertainties of using biochar as a soil amendment, and to clarify ambiguity regarding interpretation of research results. Along with several unfavourable changes in soil chemical, physical and biological properties, reduction in crop yield has been reported. Relative to controls, the yield for biochar-amended soil (application rate 0.2-20% w/w) has been reduced by 27, 11, 36, 74, and 2% for rice (Oryza sativa L.) (control 3.0 Mg ha(-1)), wheat (Triticum spp. L.) (control 4.6 Mg ha(-1)), maize (Zea mays L.) (control 4.7 Mg ha(-1)), lettuce (Lactuca sativa L.) (control 5.4 Mg ha(-1)), and tomato (Solanum lycopersicum L.) (control 265 Mg ha(-1)), respectively. Additionally, compared with unamended soils, gaseous emissions from biochar-amended soils (application rate 0.005-10% w/w) have been enhanced up to 61, 152 and 14% for CO2 (control 9.7 Mg ha(-1) year(-1)), CH4 (control 222 kg ha(-1) year(-1)), and N2O (control 4.3 kg ha(-1) year(-1)), respectively. Although biochar has the potential to mitigate several environmental problems, the data collated herein indicate that a systematic road-map for manufacturing classification of biochars, and cost-benefit analysis, must be developed before implementation of field-scale application.
  • Authors:
    • Chen, Q.
    • Wang, J. G.
    • Ren, T.
  • Source: International Society for Horticultural Science, Acta Horticulturae
  • Issue: 1018
  • Year: 2014
  • Summary: Organic manure is one of the most important factors to maintain soil fertility and achieve high yield in greenhouse vegetable production. Effects of organic manure, mineral nitrogen application and wheat straw incorporation on C cycling was investigated based on a six-year greenhouse tomato experiment in Shandong Province, northern China. In contrast to the amount of 0.14 t C ha -1 a -1 contributed by root residue, chicken manure, with 3.80 t C ha -1 a -1, was the dominant C supplement. Without any manure application, soil organic carbon and soil non-labile carbon fraction significantly decreased after 6 years of intensive tomato production. High chicken manure applied rates ranging from 13 to 20 t ha -1 a -1 only could maintain SOC content at their initial levels in the greenhouse. Based on the organic manure application, little effect of different mineral N application rate on SOC content was observed. Manure and straw incorporation significantly enhanced soil respiration rate, especially for straw incorporation, which led to higher negative net ecosystem productivity. Meanwhile no significant increase of SOC content was observed with manure and straw incorporation. High organic carbon decomposition rate due to year-round high temperature and moisture and excessive manure with low C/N ratio might be the dominant reason for the low accumulated rate of soil organic matter in this greenhouse tomato planting system. How to improve the soil organic matter further will be a great challenge in greenhouse vegetable production.