• Authors:
    • Echeverria, H.
    • Rozas, H. S.
    • Calvo, N. I. R.
    • Diovisalvi, N.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 2
  • Year: 2015
  • Summary: In-season N applications to spring wheat ( Triticum aestivum L.) may increase profits and improve N fertilizer accuracy. The objectives were to develop a calibration tool employing normalized difference vegetative index (NDVI) and SPAD 502 chlorophyll meter (SPAD) measurements for calculating the differential from the economic optimum N rate (dEONR) at growth stages Z22, Z24, and Z31 to Z39 and provide N rate algorithms for use in applying N fertilizer at a variable rate. Sensing was conducted trials over 3 yr encompassing 10 site-years across Southeastern Buenos Aires Province, Argentina. The relationship between sensor indices and dEONR was evaluated by fitting quadratic plateau (QP) regression models. Statistically significant QP models were determined at the Z24, Z31, and Z39 growth stages. Relative SPAD (rSPAD) and relative NDVI (rNDVI) reduced variation and improved the calibration of measured N stress with the dEONR. For Z31 and Z39, the rSPAD had the best goodness of fit statistics when compared to rNDVI [adjusted R2 (adj R2)=0.67 and 0.57 at Z31 and 0.68 and 0.52 at Z39, respectively]. However, adjustment at Z24 was higher for rNDVI (adj R2=0.53 and 0.61 for rSPAD and rNDVI, respectively). A single QP model to estimate the dEONR with 58% confidence was adjusted for the Z31 and Z39 growth stages. This indicates that the same calibration for N rate determination based on rSPAD or rNDVI values can be used during stem elongation in spring wheat. This model can be used as an N rate algorithm for applying N fertilizer in-season.
  • Authors:
    • Miglierina,A. M.
    • Iglesias,J. O.
    • Laurent,G. C.
    • Rodriguez,R. A.
    • Ayastuy,M. E.
    • Lobartini,J. C.
  • Source: Acta Horticulturae
  • Volume: 1076
  • Issue: 1076
  • Year: 2015
  • Summary: The application of composted organic wastes to soil can be used for conserving soil organic matter, reclaiming degraded soils and supplying plants with nutrients. Two greenhouse experiments were carried out to evaluate the addition of compost on chemical and physical properties of soils. Four different texture soils were used: Sandy soil (S1), Silty loam soil (S2), Clay loam soil (S3) (33.2 O.C. g.kg -1) and Clay loam soil (S4) (14.8 O.C. g.kg -1) cultivated with lettuce ( Lactuca sativa L.) in the Bahia Blanca region, Argentina. The application of compost had a significant effect on lettuce productivity and nutrient uptake by the crop in three of the four soil types; showing a positive effect on the dry weight, number, length and width of the leaves. The applied dose (40 Mg ha -1) modified the chemical composition of the plants: those grown in soil with added compost showed higher concentrations of nutrients than those grown in control soils. In clay loam soil (S3) no difference were found in plant productivity between treatments with and without application of compost. With respect to soil properties changes, the application of compost affected the soil pH in variable way; increased organic carbon, total nitrogen and available phosphorus. The addition of compost lowered bulk density in soils S2 and S4; increased the percentage of macropores and mesopores in S2; diminished content of mesopores and increased content of micropores at S3 and S4. The variations on chemical and physical soil properties demonstrate the benefits of compost addition, even in a short period of time.
  • Authors:
    • Garcia,G. A.
    • Dreccer,M. F.
    • Miralles,D. J.
    • Serrago,R. A.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area (GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9°C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 to 17.2°C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C -1), due to GN reductions (ca. 6% °C -1) linked to a lower number of spikes per m 2. An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change.
  • Authors:
    • Basanta, M.
    • Costantini, A.
    • Alvarez, C. R.
    • Alvarez, C.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 142
  • Year: 2014
  • Summary: Soil management affects distribution and the stocks of soil organic carbon and total nitrogen. The aim of this study was to evaluate the effect of different crop sequences and tillage systems on the vertical distribution and stocks of soil carbon and nitrogen. We hypothesized that no-tillage promotes surface organic carbon and total nitrogen accumulation, but does not affect the C and N stocks, when compared with reduced tillage. In addition, the incorporation of maize in the crop sequence increases total organic carbon and total nitrogen stocks. Observations were carried out in 2010 in an experiment located in the semiarid Argentine Pampa, on an Entic Haplustoll. A combination of three tillage systems (no tillage, no tillage with cover crop in winter and reduced tillage) and two crop sequences (soybean-maize and soybean monoculture) were assessed. After 15 years of management treatments, soil samples to a depth of 100. cm at seven intervals, were taken and analyzed for bulk density, organic carbon and total nitrogen. Total organic carbon stock up to a depth of 100. cm showed significant differences between soils under different tillage systems (reduced tillage. <. no tillage = no tillage with cover crop), the last ones having 8% more than the reduced tillage treatment. Soybean-maize had 3% more organic C up to 100. cm depth than the soybean monoculture. Total nitrogen stock was higher under no-till treatments than under reduced tillage, both at 0-50 and 0-100. cm depths. Total organic carbon stratification ratios (0-5. cm/5-10. cm) were around 1.6 under no-till and lower under reduced tillage. The stratification ratio explains less than 40% of soil carbon stock. Tillage system had a greater impact on soil carbon stock than crop sequence. © 2014 Elsevier B.V.
  • Authors:
    • Taboada, M. A.
    • Scianca, C. M.
    • Varela, M. F.
    • Rubio, G.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: Cover crops (CC) provide many benefits to soils but their effect on decomposition of previous crop residues and release of nutrients in continuous no-tillage soybean [Glycine max (L.) Merr.] production are little known. Our objective was to quantify CC effects on decomposition and phosphorus (P) release from soybean residue using litterbags. Three CC species (oat, Avena sativa L.; rye, Secale cereal L.; and rye grass, Lolium multiflorum L.) and a no CC control were evaluated. Temperature, moisture content, microbial biomass and microbial activity were measured in the surface 2cm of soil and residues. Cover crops increased soybean residue decomposition slightly both years (8.2 and 6.4%). Phosphorus release from soybean residue did not show any significant differences. Cover crops increased microbial biomass quantity and activity in both soil and residue samples (p<0.001, p=0.049 for soil and residue microbial biomass; p=0.060, p=0.003 for soil and residue microbial activity, respectively). Increased residue decomposition with CC was associated with higher soil and residue microbial biomass and activity, higher near-surface (0-2cm) moisture content (due to shading) and soil organic carbon enrichment by CC. Even though CC increased soybean residue decomposition (233kgha-1), this effect was compensated for by the annual addition of approximately 6500kgha-1 of CC biomass. This study demonstrated another role for CC when calibrating models that simulate the decomposition of residues in no-tillage systems.
  • Authors:
    • Danert, C.
    • Vera, J. C.
    • Portocarrero, R.
    • Acreche, M. M.
    • Valeiro, A. H.
  • Source: Sugar Tech
  • Volume: 16
  • Issue: 2
  • Year: 2014
  • Summary: Concentrations of greenhouse gases (GHG) in the atmosphere are increasing due to anthropogenic actions, and agriculture is one of the most important contributors. This study quantified GHG emissions from green-cane harvested sugarcane with and without post-harvest burning in Tucuman (Argentina). A field trial was conducted in Tucuman during the 2011/2012 season using a randomised complete-block design with four replications. Treatments were: (a) harvest without sugarcane burning (neither before nor after), and (b) harvest with trash burnt after harvest. The method used to capture gases (CO2, CH4 and N2O) in the crop cycle was based on closed-vented chambers, while quantification was by gas chromatography. There were significant emission rates of CO2 and N2O during the sugarcane cycle in Tucuman, but no evidence of CH4 emissions or uptakes. N2O and CO2 emission rates were higher in the no-burning treatment than in the burnt, but only in part of the crop cycle. The former is apparently associated with the application of nitrogen fertiliser, while the higher CO2 emissions seem to be associated with trash retention. There were no significant correlations between environmental factors and emission rates. Although these results seem pessimistic, in the context of an entire crop GHG balance (including the emissions due to burning before or after harvest) green-cane harvesting without burning could effectively lead to a reduction of total GHG emissions during the crop cycle.
  • Authors:
    • Laterra, P.
    • Alberto Studdert, G.
    • Horacio Villarino, S.
    • Gabriela Cendoya, M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 185
  • Year: 2014
  • Summary: Soil organic carbon (SOC) plays a vital role in determining soil quality and health, but also SOC decrease contributes significantly to the increase in atmospheric CO2 concentration. Countries need to quantify their SOC stocks and flows in order to assess their greenhouse gas emissions. To facilitate this, the Intergovernmental Panel on Climate Change has developed a simple carbon accounting method to estimate SOC stocks and flows in response to changes in land use. This method proposes three tiers for SOC change estimation. The higher the tier the greater the accuracy of the estimates, but also the complexity and the need of information. We used the RothC model to derive SOC change factors in order to develop a Tier 2 (T2) method. We applied this T2 and Tier 1 (T1) methods to estimate SOC stocks and flows in five sub regions of the Argentinean Pampa Region between 1900 and 2006. We evaluated T1 and T2 methods performances comparing their estimates against empirical data, at sub region and county scales. At both spatial scales, T1 method showed a poor performance and an important improvement was achieved with T2 method, although its performance varied among spatial scales. At sub region scale, T2 method estimates were very good (R-2 = 0.85), but at county scale the fit was poor (R-2 = 0.46). However, this poor fit may have been due, at least in part, to the quality of the input and validation information of one of the sub regions (Flooding Pampa) since its exclusion of the analysis led to an increase of the R-2 up to 0.73. Tier 2 was used to estimate the impact of land use change on SOC. Sub regions with the highest estimated SOC losses were Central Pampa, Southern Pampa - Eastern and Rolling Pampa, with 35%, 28% and 26% average SOC losses, respectively. Given that several conceptual limitations of T1 method were overcome with our simple T2 method, we conclude that T2 method is more realistic to conduct a regional SOC inventory. Besides, our T2 method was developed without using empirical information from field or laboratory studies about SOC change and, therefore, countries that have not enough empirical information available on SOC change associated to land use could derive a similar T2 method. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Priesack, E.
    • Palosuo, T.
    • Osborne, T. M.
    • Olesen, J. E.
    • O'Leary, G.
    • Nendel, C.
    • Kumar, S. Naresh
    • Mueller, C.
    • Kersebaum, K. C.
    • Izaurralde, R. C.
    • Ingwersen, J.
    • Hunt, L. A.
    • Hooker, J.
    • Heng, L.
    • Grant, R.
    • Goldberg, R.
    • Gayler, S.
    • Doltra, J.
    • Challinor, A. J.
    • Biernath, C.
    • Bertuzzi, P.
    • Angulo, C.
    • Aggarwal, P. K.
    • Martre, P.
    • Basso, B.
    • Brisson, N.
    • Cammarano, D.
    • Rotter, R. P.
    • Thorburn, P. J.
    • Boote, K. J.
    • Ruane, A. C.
    • Hatfield, J. L.
    • Jones, J. W.
    • Rosenzweig, C.
    • Ewert, F.
    • Asseng, S.
    • Ripoche, D.
    • Semenov, M. A.
    • Shcherbak, I.
    • Steduto, P.
    • Stoeckle, C.
    • Stratonovitch, P.
    • Streck, T.
    • Supit, I.
    • Tao, F.
    • Travasso, M.
    • Waha, K.
    • Wallach, D.
    • White, J. W.
    • Williams, J. R.
    • Wolf, J.
  • Source: Nature Climate Change
  • Volume: 3
  • Issue: 9
  • Year: 2013
  • Summary: Projections of climate change impacts on crop yields are inherently uncertain(1). Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate(2). However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models(1,3) are difficult(4). Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development and policy making.
  • Authors:
    • Castanheira, E. G.
    • Freire, F.
  • Source: Journal of Cleaner Production
  • Volume: 54
  • Year: 2013
  • Summary: The increase in soybean production as a source of protein and oil is being stimulated by the growing demand for livestock feed, food and numerous other applications. Significant greenhouse gas (GHG) emissions can result from land use change due to the expansion and cultivation of soybean. However, this is complex to assess and the results can vary widely. The main goal of this article is to investigate the life-cycle GHG balance for soybean produced in Latin America, assessing the implications of direct land use change emissions and different cultivation systems. A life-cycle model, including inventories for soybean produced in three different climate regions, was developed, addressing land use change, cultivation and transport to Europe. A comprehensive evaluation of alternative land use change scenarios (conversion of tropical forest, forest plantations, perennial crop plantations, savannah and grasslands), cultivation (tillage, reduced tillage and no-tillage) and soybean transportation systems was undertaken. The main results show the importance of land use change in soybean GHG emissions, but significant differences were observed for the alternative scenarios, namely 0.1-17.8 kg CO(2)eq kg(-1) soybean. The original land choice is a critical issue in ensuring the lowest soybean GHG balance and degraded grassland should preferably be used for soybean cultivation. The highest GHG emissions were calculated for tropical moist regions when rainforest is converted into soybean plantations (tillage system). When land use change is not considered, the GHG intensity varies from 0.3 to 0.6 kg CO(2)eq kg(-1) soybean. It was calculated that all tillage systems have higher GHG emissions than the corresponding no-tillage and reduced tillage systems. The results also show that N2O emissions play a major role in the GHG emissions from cultivation, although N2O emission calculations are very sensitive to the parameters and emission factors adopted.
  • Authors:
    • Divito, G.
    • Sainz Rozas, H.
    • Echeverria, H.
    • Wyngaard, N.
  • Source: Soil & Tillage Research
  • Volume: 119
  • Year: 2012
  • Summary: Agricultural management practices, such as tillage and fertilization alter soil physical, chemical and biological properties over the medium term, which has a direct impact on the system's sustainability and crop performance. The aim of this work was to evaluate how fertilization with nitrogen (N), phosphorus (P), sulphur (S), micronutrients (Mi), liming (Li) and tillage systems affect soil properties in the medium term, and to measure the impact of these changes on maize ( Zea mays L.) yield. A seven-year experiment on a Typic Argiudoll in the Southern Pampas region of Argentina using seven fertilizations treatments (Control, N P, NS, PS, NPS, NPS+Mi, and NPS+Mi+Li) and two tillage systems - conventional tillage (CT) and no-till (NT) - was evaluated. Each sub-plot was analyzed to determine physical parameters - bulk density (BD) and aggregate stability (AS)-, biological parameters - total organic carbon (TOC), carbon in the particulate fraction (COP), anaerobically incubated nitrogen (AN), total nitrogen (TN) and nitrogen in the particulate fraction (PN) - and chemical parameters - nitrate, available phosphorus, sulphate and pH - at different depths. Also, maize yield was measured in the final year without fertilizer application, in order to evaluate the effects of soil changes on this crop. Among the physical parameters, the only differences found were in BD between tillage systems in the 0-5 cm layer (1.28 g cm -3 in NT and 1.15 g cm -3 in CT). Biological parameters were unaffected by fertilization treatments. However, tillage systems modified many of them in the 0-5 cm layer: COT (17 Mg ha -1 in CT and 21 Mg ha -1 in NT), POC (2.4 Mg ha -1 in CT and 4.5 Mg ha -1 in NT), TN (1.4 Mg ha -1 in CT and 1.8 Mg ha -1 in NT), PN (0.3 Mg ha -1 in CT and 0.5 Mg ha -1 in NT) and AN (56 mg kg -1 in CT and 79 mg kg -1 in NT). These differences were not significant when the 5-20 cm depth was analyzed. Chemical properties such as pH (5.7 in treatments with N; 6.1 without N, and 6.4 with N and lime) and P Bray content were modified (35 mg kg -1 in treatments with P and 13 mg kg -1 without P). In both cases, there was interaction with the tillage system, with significant stratification under NT. Maize yield was only affected by residual P; there were no other effects of medium-term fertilization or tillage systems.