• Authors:
    • Daigh, A. L.
  • Source: Soil Survey Horizons
  • Volume: 52
  • Issue: 2
  • Year: 2011
  • Summary: Bioenergy cropping systems will supply 16 billion gallons of cellulosic ethanol by the year 2022 in an attempt to reduce U.S. dependence on gasoline. To obtain long-term energy security, bioenergy systems will need to be sustainable, especially with regard to soil. Corn stover, as a bioenergy feedstock, is of great interest due to its immediate availability for harvest with minimal change to current corn-grain cropping systems. However, traditional row crop agriculture of the United States Corn Belt has reduced soil organic matter contents, an indicator of soil quality, by as much as 40 to 60% over the last 150 yr. The harvest of corn stover will directly remove a portion of the soil organic matter input, thus further reducing soil organic matter contents. The reduction in soil organic matter contents produce direct and indirect consequences unfavorable to soil quality and productivity. Therefore, the harvest of corn stover as a long-term bioenergy feedstock is detrimental to soil, impacting soil structure and stability, erodibility, A horizon depth, and physicochemical properties. Perennial biofuel systems, in contrast, have the potential to add soil organic matter to the soil, thus offering long-term enhancement of soil quality, productivity, and formation.
  • Authors:
    • dos Santos, N. Z.
    • Dieckow, J.
    • Bayer, C.
    • Molin, R.
    • Favaretto, N.
    • Pauletti, V.
    • Piva, J. T.
  • Source: Soil & Tillage Research
  • Volume: 111
  • Issue: 2
  • Year: 2011
  • Summary: To improve C sequestration in no-till soils requires further development of crop rotations with high phytomass-C additions. The objectives of this study were (i) to assess long-term (17 years) contributions of cover crop- or forage-based no-till rotations and their related shoot and root additions to the accumulation of C in bulk and in physical fractions of a subtropical Ferralsol (20-cm depth); and (ii) infer if these rotations promote C sequestration and reach an eventual C saturation level in the soil. A wheat (Triticum aestivum L., winter crop)-soybean (Glycine max (L.) Merr, summer crop) succession was the baseline system. The soil under alfalfa (Medicago sativa L, hay forage) intercropped every three years with maize (Zea mays L., summer crop) had the highest C accumulation (0.44 Mg C ha(-1) year(-1)). The bi-annual rotation of ryegrass (Lolium multiflorum Lam., hay winter forage)-maize-ryegrass-soybean had a soil C sequestration of 0.32 Mg C ha(-1) year(-1). Among the two bi-annual cover crop-based rotations, the vetch (Vicia villosa Roth, winter cover crop)-maize-wheat-soybean rotation added 7.58 Mg C ha(-1) year(-1) as shoot plus root and sequestered 0.28 Mg C ha(-1) year(-1). The counterpart grass-based rotation of oat (Avena strigosa Schreb., winter cover crop)-maize-wheat-soybean sequestered only 0.16 Mg C ha(-1) year(-1), although adding 13% more C (8.56 Mg ha(-1) year(-1)). The vetch legume-based rotation, with a relative conversion factor (RCF) of 0.147, was more efficient in converting biomass C into sequestered soil C than oat grass-based rotation (RCF = 0.057). Soil C stocks showed a close relationship (R(2) = 0.72-0.98, P < 0.10) with root C addition, a poor relationship with total C addition and no relationship with shoot C addition. This suggests a more effective role of root than shoot additions in C accumulation in this no-till soil. Most of the C accumulation took place in the mineral-associated organic matter (71-95%, in the 0-5 cm layer) compared to the particulate organic matter. The asymptotic relationship between root C addition and C stocks in bulk soil and in mineral-associated fraction supports the idea of C saturation. In conclusion, forages or legume cover crops contribute to C sequestration in no-till tropical Ferrasols, and most of this contribution is from roots and stored in the mineral-associated fraction. This combination of soil and rotations can reach an eventual soil C saturation.
  • Authors:
    • Enfors, E.
    • Barron, J.
    • Makurira, H.
    • Rockstrom, J.
    • Tumbo, S.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 11
  • Year: 2011
  • Summary: Yield levels in smallholder farming systems in semi-arid sub-Saharan Africa are generally low. Water shortage in the root zone during critical crop development stages is a fundamental constraining factor. While there is ample evidence to show that conservation tillage can promote soil health, it has recently been suggested that the main benefit in semi-arid farming systems may in fact be an in situ water harvesting effect. In this paper we present the result from an on-farm conservation tillage experiment (combining ripping with mulch and manure application) that was carried out in North Eastern Tanzania from 2005 to 2008. Special attention was given to the effects of the tested treatment on the capacity of the soil to retain moisture. The tested conservation treatment only had a clear yield increasing effect during one of the six experimental seasons (maize grain yields increased by 41%, and biomass by 65%), and this was a season that received exceptional amounts of rainfall (549 mm). While the other seasons provided mixed results, there seemed to be an increasing yield gap between the conservation tillage treatment and the control towards the end of the experiment, and cumulatively the yield increased with 17%. Regarding soil system changes, small but significant effects on chemical and microbiological properties, but not on physical properties, were observed. This raises questions about the suggested water harvesting effect and its potential to contribute to stabilized yield levels under semi-arid conditions. We conclude that, at least in a shorter time perspective, the tested type of conservation tillage seems to boost productivity during already good seasons, rather than stabilize harvests during poor rainfall seasons. Highlighting the challenges involved in upgrading these farming systems, we discuss the potential contribution of conservation tillage towards improved water availability in the crop root zone in a longer term perspective.
  • Authors:
    • Flower, K. C.
    • Jabran, K.
    • Wahid, A.
    • Siddique, K. H. M.
    • Farooq, M.
  • Source: Soil & Tillage Research
  • Volume: 117
  • Year: 2011
  • Summary: Crop yield potential with conservation agriculture (CA) in rainfed systems is often greater than with conventional tillage (CVT) systems, particularly where sub-optimal rainfall limits yield. However, the full potential is rarely achieved because of various biotic and abiotic constraints. Analysis of 25 experiments found a slight increase in CA crop yields over time relative to CVT, indicating that CA can compete with CVT on a purely crop production basis and also has well-established environmental benefits. Evolved weed resistance to herbicides remains one of the greatest challenges to CA yields and long-term sustainability, yet there are some successful management stories. Worldwide adoption of CA is increasing; however, uptake in some regions is slow or non-existent. A lack of information on the effects and interactions of minimal soil disturbance, permanent residue cover, planned crop rotations and integrated weed management, which are key CA components, can hinder its adoption. This is because these interactions can have positive and negative effects depending on regional conditions. The positive impacts should be exploited through systems research to enhance CA crop yields. A greater focus on the influence of residue and weed management components as well as breeding for varieties adapted to biotic and abiotic stresses often associated with CA is required.
  • Authors:
    • Fernandes Cruvinel, E.
    • Bustamante, M.
    • Zepp, R.
    • Kozovits, A.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 144
  • Issue: 1
  • Year: 2011
  • Summary: In the last 40 years, a large area of savanna vegetation in Central Brazil (Cerrado) has been converted to agriculture, with intensive use of fertilizers, irrigation and management practices. Currently, the Cerrado is the main region for beef and grain production in Brazil. However, the consequences of these agricultural practices on NO, N2O and CO2 emissions from soil to atmosphere are still poorly investigated. The objectives of this study were to quantify soil emissions of NO-N, N2O-N and CO2-C in different no-till cultivation systems in comparison with native savanna vegetation. The agricultural areas included: (a) the maize and Brachiaria ruzizienses intercropping system followed by irrigated bean in rotation; (b) soybean followed by natural fallow; and (c) cotton planting over B. ruzizienses straw. The study was performed from August 2003 to October 2005 and fluxes were measured before and after planting, after fertilizations, during the growing season, before and after harvesting. NO-N fluxes in the soybean field were similar to those measured in the native vegetation. In the cornfield, higher NO-N fluxes were measured before planting than after planting and pulses were observed after broadcast fertilizations. During Brachiaria cultivation NO-N fluxes were lower than in native vegetation. In the irrigated area (bean cultivation), NO-N fluxes were also significantly higher after broadcast fertilizations. Most of the soil N2O-N fluxes measured under cultivated and native vegetation were very low (<0.6 ng N2O-N cm(-2) h(-1)) except during bean cultivation when N2O-N fluxes increased after the first and second broadcast fertilization with irrigation and during nodule senescence in the soybean field. Soil respiration values from the soybean field were similar to those in native vegetation. The CO2-C fluxes during cultivation of maize and irrigated bean were twice as high as in the native vegetation. During bean cultivation with irrigation, an increase in CO2-C fluxes was observed after broadcast fertilization followed by a decrease after the harvest. Significantly lower soil C stocks (0-30cm depth) were determined under no-tillage agricultural systems in comparison with the stocks under savanna vegetation. Fertilizer-induced emission factors of N oxides calculated from the data were lower than those indicated by the IPCC as default.
  • Authors:
    • Fisher, K. A.
    • Momen, B.
    • Kratochvil, R. J.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 2
  • Year: 2011
  • Summary: Agricultural nutrient runoff to the Chesapeake Bay has been under intense scrutiny for more than a decade in Maryland. One method for capturing these nutrients, especially N, is the use of winter cover crops. This study compared various broadcast cover crop treatments with and without soil incorporation to planting winter cover crop seed with a no-till drill. Seedling emergence and N uptake were the dependent variables measured for two planting dates and seven planting methods. The effects of planting date and planting method for winter wheat ( Triticum aestivum L.) and cereal rye ( Secale cereale L.) following corn ( Zea mays L.) harvest were investigated at two locations. The study was conducted over two winter cover crop growing seasons: 2007-2008 and 2008-2009. Treatments that incorporated the seed into the soil consistently established better stands of cover crops and took up more N regardless of fluctuations in temperature, rainfall, and planting date. Early planted cover crops consistently took up more N than those planted on the later planting date. Performance of the broadcast treatments was highly dependent on rainfall and mild temperatures for success, but did take up notable amounts of N when planted early under good growing conditions. The few differences that were found in the N uptake between wheat and rye within the same planting treatment always indicated that the rye achieved better N uptake than wheat.
  • Authors:
    • Rickman, R. W.
    • Liang, Y.
    • Albrecht, S. L.
    • Machado, S.
    • Kang, S.
    • Gollany, H. T.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 1
  • Year: 2011
  • Summary: Long-term field experiments (LTE) are ideal for predicting the influence of agricultural management on soil organic carbon (SOC) dynamics and examining biofuel crop residue removal policy questions. Our objectives were (i) to simulate SOC dynamics in LTE soils under various climates, crop rotations, fertilizer or organic amendments, and crop residue managements using the CQESTR model and (ii) to predict the potential of no-tillage (NT) management to maintain SOC stocks while removing crop residue. Classical LTEs at Champaign, IL (1876), Columbia, MO (1888), Lethbridge, AB (1911), Breton, AB (1930), and Pendleton, OR (1931) were selected for their documented history of management practice and periodic soil organic matter (SOM) measurements. Management practices ranged from monoculture to 2- or 3-yr crop rotations, manure, no fertilizer or fertilizer additions, and crop residue returned, burned, or harvested. Measured and CQESTR predicted SOC stocks under diverse agronomic practices, mean annual temperature (2.1-19 degrees C), precipitation (402-973 mm), and SOC (5.89-33.58 g SOC kg(-1)) at the LTE sites were significantly related (r(2) = 0.94, n = 186, P < 0.0001) with a slope not significantly different than 1. The simulation results indicated that the quantities of crop residue that can be sustainably harvested without jeopardizing SOC stocks were influenced by initial SOC stocks, crop rotation intensity, tillage practices, crop yield, and climate. Manure or a cover crop/intensified crop rotation under NT are options to mitigate loss of crop residue C, as using fertilizer alone is insufficient to overcome residue removal impact on SOC stocks.
  • Authors:
    • Gregoret, M. C.
    • Diaz Zorita, M.
    • Dardanelli, J.
    • Bongiovanni, R. G.
  • Source: Precision Agriculture
  • Volume: 12
  • Issue: 6
  • Year: 2011
  • Summary: In semi-arid regions, soil water and nitrogen (N) are generally limiting factors for corn ( Zea mays L.) production; hence, implementation of appropriate N fertilization strategies is needed. The use of precision agriculture practices based on specific site and crop properties may contribute to a better allocation of fertilizer among management zones (MZ). The aim of this study was to develop a model for diagnosis of N availability and recommendation of N fertilizer rates adjusted to MZ for dryland corn crops growing in Haplustolls. The model considered variability between MZ by including site-specific variables [soil available water content at sowing (SAW) and Available Nitrogen (soil available N-NO 3 at planting+applied N, Nd)] using spatial statistical analysis. The study was conducted in Cordoba, Argentina in Haplustolls and consisted in four field trials of N fertilizer (range 0-161 kg N ha -1) in each MZ. The MZ were selected based on elevation maps analysis. Grain yields varied between MZ and increased with larger SAW and Nd at sowing. Grain responses to Nd and SAW in any MZ were not different between sites, allowing to fit a regional model whose parameters (Nd, Nd 2, SAW, SAW 2) contributed significantly ( p<0.001) to yield prediction. Agronomical and economically optimum N rates varied among MZs. However, the spatial variability of optimum N rates among MZs within sites was not enough to recommend variable N fertilizer rates instead of a uniform rate. Variable N fertilizer rates should be recommended only if variability in SAW and soil N among MZ is greater than that found in this work.
  • Authors:
    • Gruber, S.
    • Möhring, J.
    • Claupein, W.
  • Source: Soil & Tillage Research
  • Volume: 115
  • Year: 2011
  • Summary: Ten years of a long-term field experiment using different strategies of conventional and conservation tillage in SW Germany were evaluated for soil mineral nitrogen (SMN) and soil moisture content. Treatments analysed were combinations of stubble tillage (S) or no stubble tillage with primary tillage P: mouldboard plough, CP: chisel plough, RTT: rototiller, NT: no-till, and VAR: alternating SIP or S/CP. Best management practices were used for crop rotation, fertilisation and plant protection. CP, VAR and NT resulted in 18.7-19.0% gravimetric water content in spring. Partially significantly lower water content was observed in spring under S/P and CP with 18.2%; P and S/RTT resulted in 18.5%. Autumn soil moisture ranged from 15.3 to 15.8% and did not significantly differ between the treatments. Interactions between treatment and depth were not significant. There was no clear trend for spring soil moisture. No treatment showed a particular response to dry or wet season. Total SMN ranged between 8 and 49 kg ha(-1) in spring and 5-26 kg ha(-1) in autumn; significant effects of the treatments or interactions of treatment x depth did not occur. The effect of the season was most relevant for the amount of SMN, probably as a result of different conditions for mineralisation. Downward movement of nitrogen in spring was low in all treatments if catch crops were grown in the previous autumn. Overall, different soil tillage methods had little effect on soil moisture and soil SMN under temperate conditions. Seriously adverse effects of any tillage treatment in terms of nitrate leaching or reduced mineralisation seem unlikely. Similarly, the tillage systems did not exhibit obvious advantages or disadvantages in terms of soil water content. An exception may have been the higher water content in autumn in 0-30 cm under high soil disturbance which provided more suitable conditions for germination of the following crop. The decision of whether or not to adopt conservation tillage in temperate climates seems not to be primarily dependent on soil moisture and nitrogen mineralisation or on nitrogen leaching.
  • Authors:
    • Jantalia, C. P.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: Converting to no-till (NT) production can affect N requirements for optimizing corn ( Zea mays L.) yields while enhancing soil organic carbon (SOC) and N levels. Nitrogen fertilization impacts on irrigated, NT continuous-corn grain, stalk, cob, and stover yields, stover C and N uptake, and C/N ratios were evaluated for 11 yr on a clay loam soil. Changes in SOC and total soil nitrogen (TSN) were also monitored. Grain, stalk, cob, and stover yields increased with increasing N rate, as did N and C uptake. The C/N ratio of stalk residue declined with increasing N rate, but cob C/N ratio was not affected, with an average stover C/N ratio of 68 at the highest N rate. Nitrogen fertilization increased SOC and TSN levels with average SOC and TSN mass rate gains with N application of 0.388, 0.321, and 0.160 Mg SOC ha -1 yr -1 and 0.063, 0.091, and 0.140 Mg TSN ha -1 yr -1 in the 0- to 7.6-, 0- to 15.2-, and 0- to 30.4-cm soil depths, respectively. The SOC and TSN mass rate changes were lower without N application. Increases in TSN appeared to be more rapid than SOC, resulting in a decline in the soil C/N ratio with time. Under irrigated, NT continuous corn production, N fertilization optimized grain and residue yields, with the enhanced benefit of increased SOC and TSN levels in the semiarid central Great Plains. Removal of cobs or partial stover residue as a cellulosic feedstock for ethanol production appears possible without negative effects on soil quality under irrigated, NT corn production.