• Authors:
    • Horton, R.
    • Ren, T.
    • Gong, Y.
    • Han, W.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 4
  • Year: 2014
  • Summary: Soil porosity is usually taken as a constant over time for a given field, although in reality it decreases with time after tillage. For the gradient method, estimating soil CO2 production with a fixed porosity may lead to large errors when soil porosity varies over time. In this study, we compared soil air-filled porosity, gas diffusivity, and CO2 production based on a temporally variable soil porosity (ΦV) with those based on a constant porosity, either initial porosity just after soil tillage (Φi) or final porosity at harvest after a tilled soil has settled (Φf). Soil porosity was measured seven times during a maize (Zea mays L.) growing season, and an exponential relationship of soil porosity with time was developed to describe ΦV for the 0- to 5-cm soil layer. Soil CO2 production was estimated from the gradient method and the mass conservation law. Soil-surface CO2 efflux was measured with a dynamic chamber throughout the growing season. The Φi value was 0.49 m3 m-3 and the Φf value was 0.43 m3 m-3. Compared with results obtained from ΦV, soil air-filled porosity, gas diffusivity, and CO2 production values obtained from Φf were 6, 11, and 22% lower, whereas values obtained from Φi were 17, 36, and 70% larger. The soil-surface CO2 effluxes estimated with ΦV better matched the chamber values than did the estimates with Φi or Φf. We conclude that use of variable soil porosity improves estimations of soil-surface CO 2 effluxes and soil CO2 production with the gradient method. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved.
  • Authors:
    • Kremer, R. J.
    • Cambardella, C. A.
    • Stott, D. E.
    • Karlen, D. L.
    • King, K. W.
    • McCarty, G. W.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Soil quality (SQ) assessment is a proactive process for evaluating soil and crop management effects on biological, chemical, and physical indicators of soil health. Our objectives were to evaluate several SQ indicators within five Agricultural Research Service (ARS) experimental watersheds (WS) and determine if those indicators were affected by manure, tillage, or crop rotation histories. Ten soil quality indicators were measured within each of 600 0 to 5 cm (0 to 2 in) depth and 398 5 to 15 cm (2 to 6 in) depth increment samples, evaluated statistically, and then scored using the Soil Management Assessment Framework. Except for soil organic carbon (C) at both depth increments or microbial biomass C and beta-glucosidase within the 5 to 15 cm increment, the indicators showed significant WS differences. Except for surface soil-test phosphorous (P), Soil Management Assessment Framework indicator scores and overall soil quality index values also showed significant (p <= 0.05) WS differences. Microbial biomass C was significantly affected by crop rotation at both sampling depths and by WS within the surface 5 cm. beta-glucosidase was significantly affected by all four factors (WS, manure, tillage, and crop rotation) and their interactions within the 0 to 5 cm increment. The water-stable macroaggregate indictor within the 0 to 5 cm increment and within the 5 to 15 cm increment, however, were not significantly different for the tillage and manure application treatments, respectively. Our study showed that the ARS Conservation Effects Assessment Project (CEAP) watersheds provided a moderately controlled example that watershed-scale monitoring of soil quality is feasible and should be used to monitor soil health and/or conservation program effectiveness.
  • Authors:
    • Yimer, F.
    • Ketema, H.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 141
  • Year: 2014
  • Summary: With the objectives of assessing variations in selected soil properties, two tillage types: agroforestry based conservation tillage (AFCST) and maize based conventional tillage (MCVT) under three age categories (5, 10 and 15-years) were selected in Chichu and Haroresa Kebels, Dilla Zuria, Ethiopia. A total of 48 composite soil samples (4 replication×2 tillage types×3 age categories×2 soil depth layers: 0-10cm and 10-20cm) were collected to analyze texture and soil organic carbon (SOC%). Addational undisturbed core samples were also collected to determine soil bulk density (gcm-3). Water infiltration capacity was also measured in the field using double ring infiltrometer. The results showed that clay and sand textural fractions significantly varied (p<0.001, p=0.002, respectively) with age of land management. Soil bulk density, soil moisture content (SMC), total porosity (Pt) and soil organic carbon (SOC) varied significantly with tillage types (p<0.001) and soil depth (p<0.001). Water infiltration (rate and cumulative) significantly varied (p<0.001) with tillage types: higher in the AFCST than in the MCVT. Lower soil bulk density, higher soil organic carbon (SOC) and soil moisture content (SMC) were observed in the top 0-10cm soil layer under the AFCST than in the MCVT. Soil bulk density and soil moisture content (SMC) increased while total porosity (Pt) and soil organic carbon (SOC) decreased with soil depth in both tillage types. Improvement in the soil properties under AFCST was due to higher soil organic matter (SOM) input and less soil disturbance. Thus, reducing the frequency of soil disturbance through application of conservation tillage would help to improve the soil quality. © 2014 Elsevier B.V.
  • Authors:
    • Deichman, C. L.
    • Kremer, R. J.
  • Source: AGRONOMY JOURNAL
  • Volume: 106
  • Issue: 5
  • Year: 2014
  • Summary: The solar corridor crop system (SCCS) is designed for improved crop productivity based on highly efficient use of solar radiation by integrating row crops with drilled or solid-seeded crops in broad strips (corridors) that also facilitate establishment of cover crops for year-round soil cover. The SCCS is an agroecosystem with diverse system structure that should inherently provide many features to build soil quality. Management strategies include reduced tillage, intercropping, and soil conservation through crop residue retention, which are associated with improved soil quality attributes of enhanced C and N content, effective nutrient cycling, and high microbial activity. Our objective was to evaluate the effect of SCCS in 76- and 152-cm (corridor) row widths on selected soil quality indicators as an assessment of soil quality during establishment of SCCS. Microbial activity, measured as soil glucosidase activity, was highest in rhizosphere soils planted to corn ( Zea mays L.) hybrids at 74,000 plants ha -1 regardless of row width. However, soil glucosidase activity was strongly correlated ( r2=0.72) with active carbon (AC), and showed trends for increased contents in rows bordering the corridor. This suggested that increased carbon fixation by plants at the wide row spacing due to greater exposure to solar radiation also increased carbon substrates released into the rhizosphere for microbial metabolism. The limited soil quality assessment conducted in this study demonstrated that an integrated cropping system represented by the SCCS offers an effective management system for maintaining crop production while promoting soil quality and soil conservation.
  • Authors:
    • Venterea, R. T.
    • Maharjan, B.
  • Source: JOURNAL OF ENVIRONMENTAL QUALITY Pages:
  • Volume: 43
  • Issue: 5
  • Year: 2014
  • Summary: Anhydrous ammonia (AA) is a major fertilizer source in North America that can promote greater emissions of nitrous oxide (N 2O) than other nitrogen (N) fertilizers. Previous studies found that injection of AA at a shallow depth (0.1 m) decreased N 2O in a rainfed clay loam but increased N 2O in an irrigated loamy sand compared with the standard injection depth of 0.2 m. The objective of this study was to evaluate the effects of AA injection depth in a silt loam soil used for corn ( Zea mays L.) production and managed under two contrasting tillage regimes over two consecutive growing seasons (2010 and 2011) in Minnesota. In contrast with previous studies, AA placement depth did not affect N 2O emissions in either tillage system or in either growing season. Tillage by itself affected N 2O emissions only in the drier of two seasons, during which N 2O emissions under no tillage (NT) exceeded those under conventional tillage (CT) by 55%. Soil moisture content under NT was also greater than under CT only in the drier of the two seasons. Effects of AA placement depth and long-term tillage regime on N 2O emissions exhibit intersite as well as interannual variation, which should be considered when developing N 2O mitigation strategies. Further study is needed to identify specific soil, climate, or other factors that mediate the contrasting responses to management practices across sites.
  • Authors:
    • Adhya, T. K.
    • Singh Bohra, J.
    • Agrawal, M.
    • Pandey, D.
    • Bhattacharyya, P.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: In order to utilize agricultural soils as an option to offset atmospheric carbon, it is essential to ascertain the degree of stability of the accrued carbon. A two step acid hydrolysis technique was used to separate labile and recalcitrant carbon pools in soil upto 30cm depth to analyze their responses to different tillage managements after eight years of continuous practice in a sub-humid tropical rice-wheat system of Indo-Gangetic plains. There were four tillage practices; tillage before sowing/transplantation of every crop (RCT-WCT), tillage before transplanting of rice but no tillage before sowing the succeeding wheat crop (RCT-WNT), tillage before sowing of wheat but no tillage before sowing of rice (RNT-WCT), and no tillage before sowing of rice as well as wheat (RNT-WNT). It was observed that reduction in tillage frequency enhanced the total and recalcitrant carbon contents in soil with the maximum rate of sequestration recorded under RNT-WNT (0.59tCha-1yr-1). The fraction of carbon translated into recalcitrant pool was constant under all the tillage combinations indicating that carbon stabilization was dependent predominantly on organic matter input in the rice-wheat system. Conventional tillage on the other hand caused loss of carbon from the soil as observed by reduction in total soil carbon content under RCT-WCT. Reduction in recalcitrant carbon content under RCT-WCT further indicated that acid hydrolysis might not represent long term carbon accumulation reliably. Concentration of phenolics in labile pool increased under RNT-WNT, RCT-WNT and RNT-WCT practices which also had higher total and recalcitrant carbon pools. This indicated towards contribution of phenolics in carbon stabilization in the soil. Results of the present study further suggested that adoption of no till agriculture in the region offers significant carbon sequestration opportunity under proper agricultural management.
  • Authors:
    • Cantero-Martínez, C.
    • Álvaro-Fuentes, J.
    • Plaza-Bonilla, D.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 139
  • Year: 2014
  • Summary: Agricultural management practices play a major role in the process of SOC sequestration. However, the large background of stable carbon (C) already present in the soil and the long period of time usually required to observe changes in soil organic carbon (SOC) stocks have increased the necessity to identify soil C fractions with a fast response to changes in agricultural management practices. Consequently, we quantified the response of total SOC, permanganate oxidizable organic carbon (POxC), particulate organic carbon (POC) and the carbon concentration of water-stable macroaggregates, microaggregates within macroaggregates and the silt-plus clay-sized fraction (M-C, mM-C, s+cM-C, respectively) to changes in management. We chose a long-term tillage and N fertilization field experiment (18 years) located in NE Spain. In the first 5. cm depth under no-tillage (NT) compared with conventional tillage (CT), the POxC fraction and total SOC increased similarly (about 59%). However, other C pools studied (i.e., M-C, M-POxC, mM-C, POC and s+cM-C) had lower increases with values ranging from 17% to 31%. For the 5-20 and 20-40. cm soil depths, the POC was the most sensitive fraction to tillage with 46% and 54% decrease when NT was compared to CT, respectively. Likewise, the POC fraction presented the highest response to N fertilization in the three depths studied (i.e., 0-5, 5-20 and 20-40. cm). The mM-C and s+cM-C fractions presented the lowest sensitivity to changes in tillage and N fertilization management. Our results showed that the POC fraction had the greatest sensitivity to changes in agricultural management practices, proving its ability as an early indicator of optimized practices to sequester C in soil.
  • Authors:
    • Cassman, K. G.
    • Sanchez, P. A.
    • Palm, C. A.
    • Gerard, B. G.
    • Jat, M. L.
    • Stirling, C. M.
    • Powlson, D. S.
  • Source: NATURE CLIMATE CHANGE
  • Volume: 4
  • Issue: 8
  • Year: 2014
  • Summary: The Emissions Gap Report 2013 from the United Nations Environment Programme restates the claim that changing to no-till practices in agriculture, as an alternative to conventional tillage, causes an accumulation of organic carbon in soil, thus mitigating climate change through carbon sequestration. But these claims ignore a large body of experimental evidence showing that the quantity of additional organic carbon in soil under no-till is relatively small: in large part apparent increases result from an altered depth distribution. The larger concentration near the surface in no-till is generally beneficial for soil properties that often, though not always, translate into improved crop growth. In many regions where no-till is practised it is common for soil to be cultivated conventionally every few years for a range of agronomic reasons, so any soil carbon benefit is then lost. We argue that no-till is beneficial for soil quality and adaptation of agriculture to climate change, but its role in mitigation is widely overstated.
  • Authors:
    • Caesar-TonThat, T.
    • Stevens, W. B.
    • Sainju, U. M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 3
  • Year: 2014
  • Summary: Management practices are needed to reduce soil C losses from croplands converted from Conservation Reserve Program (CRP) grassland. We evaluated the effects of irrigation, tillage, cropping system, and N fertilization on surface residue and soil organic C (SOC) at the 0- to 85-cm depth in relation to crop yields in a sandy loam soil from 2005 to 2011 in croplands converted from CRP in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) as the main plot and six cropping systems [CRP, conventional till malt barley (Hordeum vulgare L.) with N fertilizer (CTBN), conventional till malt barley without N fertilizer (CTBO), no-till malt barley- pea (Pisum sativum L.) with N fertilizer (NTB-P), no-till malt barley with N fertilizer (NTBN), and no-till malt barley without N fertilizer (NTBO)] as the split plot arranged in a randomized complete block with three replications. Soil surface residue amount and C content were greater in CRP and NTBN than the other cropping systems. At 0 to 5 cm, SOC was greater in irrigated CRP, but at 0 to 85 cm it was greater in nonirrigated NTBN than most other treatments. At 0 to 20 cm, SOC increased by 0.26 to 1.21 Mg C ha-1 yr-1 in NTB-P and CRP but decreased by 0.02 to 0.68 Mg C ha-1 yr-1 in other cropping systems. Surface residue C and SOC at 0 to 10 cm were related to annualized crop grain yield (R2 = 0.45-0.77, P x≤ 0.12, n = 10). Because of positive C sequestration rate and favorable crop yields, NTB-P may be used as a superior management option to reduce soil C losses and sustain yields in croplands converted from CRP in the northern Great Plains.
  • Authors:
    • Caesar-Tonthat, T.
    • Stevens, W. B.
    • Sainju, U. M.
    • Montagne, C.
  • Source: AGRONOMY JOURNAL
  • Volume: 106
  • Issue: 5
  • Year: 2014
  • Summary: Management practices are needed to reduce N losses from croplands converted from Conservation Reserve Program (CRP). We evaluated the effects of irrigation, tillage, cropping system, and N fertilization on surface residue N, soil total nitrogen (STN), NH 4-N, and NO 3-N at the 0- to 85-cm depth in a sandy loam from 2005 to 2011 in croplands converted from CRP in western North Dakota. Treatments were two irrigation practices (irrigated vs. non-irrigated) and six cropping systems (CRP, conventional till malt barley [ Hordeum vulgaris L.] with nitrogen fertilizer [CTBN], conventional till malt barley without nitrogen fertilizer [CTBO], no-till malt barley-pea ( Pisum sativum L.) with nitrogen fertilizer [NTB-P], no-till malt barley with nitrogen fertilizer [NTBN], and no-till malt barley without nitrogen fertilizer [NTBO]). Surface residue N was greater in non-irrigated CRP than irrigated and non-irrigated CTBN, CTBO, and NTBO and non-irrigated NTB-P. Soil total N at 0 to 10 cm was greater in irrigated CRP, but at 0 to 85 cm was greater in non-irrigated NTBN than irrigated CRP, CTBN, CTBO, and NTBO and non-irrigated NTB-P. Soil NH 4-N content at 0 to 20 cm was also greater in irrigated CRP than irrigated and non-irrigated CTBO, NTB-P, and NTBO. Soil NO 3-N at 0 to 85 cm was greater in NTB-P than CRP, CTBO, and NTBO. Because of increased soil N sequestration and NO 3-N level, irrigated NTB-P may be used to reduce soil N losses and optimize N availability compared to other treatments in croplands converted from CRP.