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Agronomy, Volume 3, Issue 2 (June 2013) – 15 articles , Pages 256-507

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1030 KiB  
Article
Evaluation of Low Pressure Fogging System for Improving Crop Yield of Tomato (Lycopersicon esculentum Mill.): Grown under Heat Stress Conditions
by Danny Harel, Hadar Fadida, Shelly Gantz, Kobi Shilo and Hagai Yasuor
Agronomy 2013, 3(2), 497-507; https://doi.org/10.3390/agronomy3020497 - 19 Jun 2013
Cited by 16 | Viewed by 6236
Abstract
In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September) in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most [...] Read more.
In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September) in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most cases these net houses have a flat roof and no ventilation or climate control measures. This insufficient ventilation during the hot summer leads to above optimal air temperatures and causes moderate heat stress inside the shelters, which leads to yield reduction. The aim of this study was to evaluate the ability of a simple and inexpensive low pressure fogging system installed in a naturally ventilated net house to lower temperatures and improve the yield during the summer. The study showed that in areas where relative air humidity (RH) during the daytime is less than 60%, tomato plants improved their performance when grown through the summer in net houses under moderate heat stress. Under fogging conditions pollen grain viability and fruit set were significantly improved. This improvement influenced the yield picked during September (104–136 DAP). However, total seasonal yield was not affected by the fogging treatment. Full article
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292 KiB  
Article
The Impact of Volunteer Corn on Crop Yields and Insect Resistance Management Strategies
by Paul T. Marquardt, Ryan M. Terry and William G. Johnson
Agronomy 2013, 3(2), 488-496; https://doi.org/10.3390/agronomy3020488 - 14 Jun 2013
Cited by 12 | Viewed by 6325
Abstract
Volunteer corn (VC) has reemerged as a problematic weed in corn/soybean rotational cropping systems. This reemergence and increasing prevalence of volunteer corn has been correlated to an increased adoption of herbicide-resistant (HR) corn hybrids and the adoption of conservation tillage. Since the introduction [...] Read more.
Volunteer corn (VC) has reemerged as a problematic weed in corn/soybean rotational cropping systems. This reemergence and increasing prevalence of volunteer corn has been correlated to an increased adoption of herbicide-resistant (HR) corn hybrids and the adoption of conservation tillage. Since the introduction of HR crops, control options, weed/crop competition, and other concerns (i.e., insect resistance management of Bt traits) have increased the amount of attention that volunteer corn is receiving. The objective of this review is to discuss what is known about VC prior to and after the introduction of HR crops, and to discuss new information about this important weed. Full article
(This article belongs to the Special Issue Weed Management and Herbicide Resistance)
516 KiB  
Article
Glyphosate-Resistant Goosegrass from Mississippi
by William T. Molin, Alice A. Wright and Vijay K. Nandula
Agronomy 2013, 3(2), 474-487; https://doi.org/10.3390/agronomy3020474 - 29 May 2013
Cited by 54 | Viewed by 6439
Abstract
A suspected glyphosate-resistant goosegrass [Eleusine indica (L.) Gaertn.] population, found in Washington County, Mississippi, was studied to determine the level of resistance and whether the resistance was due to a point mutation, as was previously identified in a Malaysian population. Whole plant [...] Read more.
A suspected glyphosate-resistant goosegrass [Eleusine indica (L.) Gaertn.] population, found in Washington County, Mississippi, was studied to determine the level of resistance and whether the resistance was due to a point mutation, as was previously identified in a Malaysian population. Whole plant dose response assays indicated a two- to four-fold increase in resistance to glyphosate. Leaf disc bioassays based on a glyphosate-dependent increase in shikimate levels indicated a five- to eight-fold increase in resistance. Sequence comparisons of messenger RNA for epsps, the gene encoding the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, from resistant and sensitive goosegrass, revealed a cytosine to thymine nucleotide change at position 319 in the resistant accessions. This single nucleotide polymorphism causes a proline to serine amino acid substitution at position 106 in 5-enolpyruvylshikimate-3-phosphate synthase. A real-time polymerase chain reaction assay using DNA probes specific for the nucleotide change at position 319 was developed to detect this polymorphism. Goosegrass from 42 locations were screened, and the results indicated that glyphosate-resistant goosegrass remained localized to where it was discovered. Pendimethalin, s-metolachlor, clethodim, paraquat and fluazifop controlled resistant goosegrass 93% to 100%, indicating that several control options for glyphosate-resistant goosegrass are available. Full article
(This article belongs to the Special Issue Weed Management and Herbicide Resistance)
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319 KiB  
Review
The Application of Biochar in the EU: Challenges and Opportunities
by Luca Montanarella and Emanuele Lugato
Agronomy 2013, 3(2), 462-473; https://doi.org/10.3390/agronomy3020462 - 22 May 2013
Cited by 85 | Viewed by 10480
Abstract
Biochar application to agricultural soils is an interesting emerging technology with promising potential for long-term carbon storage, sustainable waste disposal, and soil fertility enhancement. Extensive information exists in the literature on the highly beneficial properties of biochar. Nevertheless, systematic application of biochar on [...] Read more.
Biochar application to agricultural soils is an interesting emerging technology with promising potential for long-term carbon storage, sustainable waste disposal, and soil fertility enhancement. Extensive information exists in the literature on the highly beneficial properties of biochar. Nevertheless, systematic application of biochar on European agricultural soils may have wide ranging policy implications as well as environmental and public health concerns. In this paper we critically review existing scientific evidence from a European policy perspective and identify research gaps for future comprehensive assessments of the policy, environmental, economic, and health implications of the systematic use of biochar in European agricultural soils. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
742 KiB  
Review
Use of Wild Relatives and Closely Related Species to Adapt Common Bean to Climate Change
by Timothy G. Porch, James S. Beaver, Daniel G. Debouck, Scott A. Jackson, James D. Kelly and Hannes Dempewolf
Agronomy 2013, 3(2), 433-461; https://doi.org/10.3390/agronomy3020433 - 10 May 2013
Cited by 100 | Viewed by 14318
Abstract
Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide. However, abiotic and biotic stress limits bean yields to <600 kg ha−1 in low-income countries. Current low yields result in food insecurity, while demands for increased yields to match the [...] Read more.
Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide. However, abiotic and biotic stress limits bean yields to <600 kg ha−1 in low-income countries. Current low yields result in food insecurity, while demands for increased yields to match the rate of population growth combined with the threat of climate change are significant. Novel and significant advances in genetic improvement using untapped genetic diversity available in crop wild relatives and closely related species must be further explored. A meeting was organized by the Global Crop Diversity Trust to consider strategies for common bean improvement. This review resulted from that meeting and considers our current understanding of the genetic resources available for common bean improvement and the progress that has been achieved thus far through introgression of genetic diversity from wild relatives of common bean, and from closely related species, including: P. acutifolius, P. coccineus, P. costaricensis and P. dumosus. Newly developed genomic tools and their potential applications are presented. A broad outline of research for use of these genetic resources for common bean improvement in a ten-year multi-disciplinary effort is presented. Full article
(This article belongs to the Special Issue Sustainable Crop Production)
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181 KiB  
Review
New Approaches for Crop Genetic Adaptation to the Abiotic Stresses Predicted with Climate Change
by Robert Redden
Agronomy 2013, 3(2), 419-432; https://doi.org/10.3390/agronomy3020419 - 10 May 2013
Cited by 34 | Viewed by 7638
Abstract
Extreme climatic variation is predicted with climate change this century. In many cropping regions, the crop environment will tend to be warmer with more irregular rainfall and spikes in stress levels will be more severe. The challenge is not only to raise agricultural [...] Read more.
Extreme climatic variation is predicted with climate change this century. In many cropping regions, the crop environment will tend to be warmer with more irregular rainfall and spikes in stress levels will be more severe. The challenge is not only to raise agricultural production for an expanding population, but to achieve this under more adverse environmental conditions. It is now possible to systematically explore the genetic variation in historic local landraces by using GPS locators and world climate maps to describe the natural selection for local adaptation, and to identify candidate germplasm for tolerances to extreme stresses. The physiological and biochemical components of these expressions can be genomically investigated with candidate gene approaches and next generation sequencing. Wild relatives of crops have largely untapped genetic variation for abiotic and biotic stress tolerances, and could greatly expand the available domesticated gene pools to assist crops to survive in the predicted extremes of climate change, a survivalomics strategy. Genomic strategies can assist in the introgression of these valuable traits into the domesticated crop gene pools, where they can be better evaluated for crop improvement. The challenge is to increase agricultural productivity despite climate change. This calls for the integration of many disciplines from eco-geographical analyses of genetic resources to new advances in genomics, agronomy and farm management, underpinned by an understanding of how crop adaptation to climate is affected by genotype × environment interaction. Full article
294 KiB  
Article
The Impact of Biochar Application on Soil Properties and Plant Growth of Pot Grown Lettuce (Lactuca sativa) and Cabbage (Brassica chinensis)
by Sarah Carter, Simon Shackley, Saran Sohi, Tan Boun Suy and Stephan Haefele
Agronomy 2013, 3(2), 404-418; https://doi.org/10.3390/agronomy3020404 - 07 May 2013
Cited by 187 | Viewed by 22804
Abstract
The effect of rice-husk char (potentially biochar) application on the growth of transplanted lettuce (Lactuca sativa) and Chinese cabbage (Brassica chinensis) was assessed in a pot experiment over a three crop (lettuce-cabbage-lettuce) cycle in Cambodia. The biochar was the [...] Read more.
The effect of rice-husk char (potentially biochar) application on the growth of transplanted lettuce (Lactuca sativa) and Chinese cabbage (Brassica chinensis) was assessed in a pot experiment over a three crop (lettuce-cabbage-lettuce) cycle in Cambodia. The biochar was the by-product of a rice-husk gasification unit and consisted of 28.7% carbon (C) by mass. Biochar application rates to potting medium of 25, 50 and 150 g kg−1 were used with and without locally available fertilizers (a mixture of compost, liquid compost and lake sediment). The rice-husk biochar used was slightly alkaline (pH 7.79), increased the pH of the soil, and contained elevated levels of some trace metals and exchangeable cations (K, Ca and Mg) in comparison to the soil. The biochar treatments were found to increase the final biomass, root biomass, plant height and number of leaves in all the cropping cycles in comparison to no biochar treatments. The greatest biomass increase due to biochar additions (903%) was found in the soils without fertilization, rather than fertilized soils (483% with the same biochar application as in the “without fertilization” case). Over the cropping cycles the impact was reduced; a 363% increase in biomass was observed in the third lettuce cycle. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
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1345 KiB  
Article
Variation in Protein Content and Amino Acids in the Leaves of Grain, Vegetable and Weedy Types of Amaranths
by Rita Andini, Shigeki Yoshida and Ryo Ohsawa
Agronomy 2013, 3(2), 391-403; https://doi.org/10.3390/agronomy3020391 - 03 May 2013
Cited by 33 | Viewed by 7543
Abstract
Malnutrition has affected almost 31% of pre-school children. This paper provides the information of nutritional values (leaf protein, 15 amino acids, biomass and leaf dry matter) of grain, vegetable and weedy types of amaranths (n = 76 accessions); particularly those novel materials [...] Read more.
Malnutrition has affected almost 31% of pre-school children. This paper provides the information of nutritional values (leaf protein, 15 amino acids, biomass and leaf dry matter) of grain, vegetable and weedy types of amaranths (n = 76 accessions); particularly those novel materials originated from the highland areas of Sumatra-Takengon. The highest values of leaf protein and total amino acids were found in many weedy species (A. viridis, A. blitum L. and A. dubius). The ranges of leaf protein and total amino acids in most of weedy types were 12–29 g 100 g−1 DM and 84–93 g 100 g−1 DW protein, respectively. The leaves of amaranths were found to be a good source for lysine which is the limiting essential amino acids in most of cereal plants. Their values were in the range of 6 g 100 g−1 DW protein which are close to that of good protein quality according to FAO/WHO’s standard. The leaves of underutilized weedy species of A. dubius, A. blitum, A. viridis and the dual purpose types of A. caudatus L., A. cruentus L. deserve to be further exploited as a low cost solution for solving malnutrition problems, especially in Indonesia. Full article
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940 KiB  
Article
Screening for Barley Waterlogging Tolerance in Nordic Barley Cultivars (Hordeum vulgare L.) Using Chlorophyll Fluorescence on Hydroponically-Grown Plants
by Nils-Ove Bertholdsson
Agronomy 2013, 3(2), 376-390; https://doi.org/10.3390/agronomy3020376 - 25 Apr 2013
Cited by 267 | Viewed by 6871
Abstract
Waterlogging can reduce crop yield by 20%–50% or more, and lack of efficient selection methods is an obstacle in plant breeding. The methods currently used are mainly indices based on germination ability in Petri dishes and leaf chlorosis in plants grown in waterlogged [...] Read more.
Waterlogging can reduce crop yield by 20%–50% or more, and lack of efficient selection methods is an obstacle in plant breeding. The methods currently used are mainly indices based on germination ability in Petri dishes and leaf chlorosis in plants grown in waterlogged soils. Cultivation in oxygen-depleted nutrient solution is the ultimate waterlogging system. Therefore methods based on root growth inhibition and on fluorescence in plant material hydroponically grown in oxygen-depleted solution were evaluated against data on biomass accumulation in waterlogged soils. Both traits were correlated with waterlogging tolerance in soil, but since it was easier to measure fluorescence, this method was further evaluated. A selection of F2 plants with high and low fluorescence revealed a small but significant screening effect in F3 plants. A test of 175 Nordic cultivars showed large variations in chlorophyll fluorescence in leaves from oxygen-stressed seedlings, indicating that adaptation to waterlogging has gradually improved over the past 40–50 years with the introduction of new cultivars onto the market. However, precipitation also increased during the period and new cultivars may have inadvertently been adapted to this while breeding barley for grain yield. The results suggest that the hydroponic method can be used for screening barley populations, breeding lines or phenotyping of populations in developing markers for quantitative trait loci. Full article
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312 KiB  
Review
Impact of Biochar on Organic Contaminants in Soil: A Tool for Mitigating Risk?
by Uchenna Ogbonnaya and Kirk T. Semple
Agronomy 2013, 3(2), 349-375; https://doi.org/10.3390/agronomy3020349 - 23 Apr 2013
Cited by 90 | Viewed by 11735
Abstract
The presence of biochar in soils through natural processes (forest fires, bush burning) or through application to soil (agriculture, carbon storage, remediation, waste management) has received a significant amount of scientific and regulatory attention. Biochar alters soil properties, encourages microbial activity and enhances [...] Read more.
The presence of biochar in soils through natural processes (forest fires, bush burning) or through application to soil (agriculture, carbon storage, remediation, waste management) has received a significant amount of scientific and regulatory attention. Biochar alters soil properties, encourages microbial activity and enhances sorption of inorganic and organic compounds, but this strongly depends on the feedstock and production process of biochar. This review considers biochar sources, the production process and result of pyrolysis, interactions of biochar with soil, and associated biota. Furthermore, the paper focuses on the interactions between biochar and common anthropogenic organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), pesticides, and dioxins, which are often deposited in the soil environment. It then considers the feasibility of applying biochar in remediation technologies in addition to other perspective areas yet to be explored. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
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170 KiB  
Article
Downy Brome (Bromus tectorum L.) and Broadleaf Weed Control in Winter Wheat with Acetolactate Synthase-Inhibiting Herbicides
by Seshadri S. Reddy, Phillip W. Stahlman and Patrick W. Geier
Agronomy 2013, 3(2), 340-348; https://doi.org/10.3390/agronomy3020340 - 18 Apr 2013
Cited by 12 | Viewed by 6175
Abstract
A study was conducted for three seasons in northwest Kansas, USA to evaluate acetolactate synthase (ALS)-inhibiting herbicides for downy brome (Bromus tectorum L.) and winter annual broadleaf weed control in winter wheat. Herbicides included pyroxsulam at 18.4 g ai ha−1, [...] Read more.
A study was conducted for three seasons in northwest Kansas, USA to evaluate acetolactate synthase (ALS)-inhibiting herbicides for downy brome (Bromus tectorum L.) and winter annual broadleaf weed control in winter wheat. Herbicides included pyroxsulam at 18.4 g ai ha−1, propoxycarbazone-Na at 44 g ai ha−1, premixed propoxycarbazone-Na & mesosulfuron-methyl at 27 g ai ha−1, and sulfosulfuron at 35 g ai ha−1. The herbicides were applied postemergence in fall and spring seasons. Averaged over time of application, no herbicide controlled downy brome more than 78% in any year. When downy brome densities were high, control was less than 60%. Pyroxsulam controlled downy brome greater than or similar to other herbicides tested. Flixweed (Descurainia sophia L.), blue mustard [Chorispora tenella (Pallas) DC.], and henbit (Lamium amplexicaule L.) control did not differ among herbicide treatments. All herbicides tested controlled flixweed and blue mustard at least 87% and 94%, respectively. However, none of the herbicides controlled henbit more than 73%. Fall herbicide applications improved weed control compared to early spring applications; improvement ranged from 3% to 31% depending on the weed species. Henbit control was greatly decreased by delaying herbicide applications until spring compared to fall applications (49% vs. 80% control). Herbicide injury was observed in only two instances. The injury was ≤13% with no difference between herbicides and the injury did not impact final plant height or grain yield. Full article
(This article belongs to the Special Issue Weed Management and Herbicide Resistance)
306 KiB  
Review
Biochar Impacts on Soil Physical Properties and Greenhouse Gas Emissions
by Atanu Mukherjee and Rattan Lal
Agronomy 2013, 3(2), 313-339; https://doi.org/10.3390/agronomy3020313 - 18 Apr 2013
Cited by 357 | Viewed by 24834
Abstract
Biochar, a co-product of a controlled pyrolysis process, can be used as a tool for sequestering C in soil to offset greenhouse gas (GHG) emissions, and as a soil amendment. Whereas the impacts of biochar application on soil chemical properties are widely known, [...] Read more.
Biochar, a co-product of a controlled pyrolysis process, can be used as a tool for sequestering C in soil to offset greenhouse gas (GHG) emissions, and as a soil amendment. Whereas the impacts of biochar application on soil chemical properties are widely known, the research information on soil physical properties is scarce. The objectives of this review are to (i) synthesize available data on soil physical properties and GHG emissions, (ii) offer possible mechanisms related to the biochar-amended soil processes, and (iii) identify researchable priorities. Application rates of 1%–2% (w/w) of biochar can significantly improve soil physical quality in terms of bulk density (BD), and water holding capacity (WHC). However, little data are available on surface area (SA), aggregation stability, and penetration resistance (PR) of biochar-amended soil. While biochar amendment can initially accentuate the flux of carbon dioxide (CO2), the emission of GHGs may be suppressed over time. A 2-phase complexation hypothesis is proposed regarding the mechanisms of the interaction between soil and biochar. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
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620 KiB  
Article
Characterization and Mineralization Rates of Low Temperature Peanut Hull and Pine Chip Biochars
by Keith Harris, Julia Gaskin, Miguel Cabrera, William Miller and K.C. Das
Agronomy 2013, 3(2), 294-312; https://doi.org/10.3390/agronomy3020294 - 16 Apr 2013
Cited by 76 | Viewed by 7780
Abstract
Biochar can potentially increase soil fertility and sequester carbon by incorporating nutrients and stable black carbon into the soil; however its effect on soil nitrogen (N) and carbon (C) processes is not well understood. A defined methodology to characterize biochar is necessary to [...] Read more.
Biochar can potentially increase soil fertility and sequester carbon by incorporating nutrients and stable black carbon into the soil; however its effect on soil nitrogen (N) and carbon (C) processes is not well understood. A defined methodology to characterize biochar is necessary to predict how specific biochars will affect C and N mineralization. We amended a Tifton soil (Fine-loamy, siliceous, thermic Plinthic Kandiudults) with peanut hull (Arachis hypogaea; PH; 2.1% N) and pine chip (Pinus taeda; PC: 0.4% N) biochar at application rates of 1% and 2% (w/w) and performed a 136-day mineralization study. A companion 24-day mineralization study amended Tifton soil with PH and PC biochar at 2% and their respective feedstocks at equal C rates. Soil C mineralization rates were monitored periodically throughout each study and total N mineralization rates were also measured. In addition, we characterized each biochar using thermogravimetric analysis with mass spectrometer (TGA-MS), proximate analysis, Fourier transform infrared spectroscopy (FTIR), and total mineral analysis to identify biochar characteristics that might correlate with mineralization properties. Limited C (<2%) mineralized from both biochars, but mineralization rates of soil amended with PH biochar were higher than PC biochar. Carbon mineralization correlated well with estimated aliphatic content determined by TGA-MS but not with volatile content indicated by proximate analysis. Nitrogen was not mineralized from either biochar, indicating that plant-based biochar should not be considered a source of N for plant growth. The N in biochar may be contained in the stable aromatic structure of the biochar, as indicated by TGA-MS, and not available to soil microbes. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
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219 KiB  
Review
A Review of Biochar and Soil Nitrogen Dynamics
by Tim J. Clough, Leo M. Condron, Claudia Kammann and Christoph Müller
Agronomy 2013, 3(2), 275-293; https://doi.org/10.3390/agronomy3020275 - 16 Apr 2013
Cited by 657 | Viewed by 33187
Abstract
Interest in biochar stems from its potential agronomic benefits and carbon sequestration ability. Biochar application alters soil nitrogen (N) dynamics. This review establishes emerging trends and gaps in biochar-N research. Biochar adsorption of NO3, up to 0.6 mg g−1 [...] Read more.
Interest in biochar stems from its potential agronomic benefits and carbon sequestration ability. Biochar application alters soil nitrogen (N) dynamics. This review establishes emerging trends and gaps in biochar-N research. Biochar adsorption of NO3, up to 0.6 mg g−1 biochar, occurs at pyrolysis temperatures >600 °C with amounts adsorbed dependent on feedstock and NO3 concentration. Biochar NH4+ adsorption depends on feedstock, but no pyrolysis temperature trend is apparent. Long-term practical effectiveness of inorganic-N adsorption, as a NO3 leaching mitigation option, requires further study. Biochar adsorption of ammonia (NH3) decreases NH3 and NO3 losses during composting and after manure applications, and offers a mechanism for developing slow release fertilisers. Reductions in NH3 loss vary with N source and biochar characteristics. Manure derived biochars have a role as N fertilizers. Increasing pyrolysis temperatures, during biochar manufacture from manures and biosolids, results in biochars with decreasing hydrolysable organic N and increasing aromatic and heterocyclic structures. The short- and long-term implications of biochar on N immobilisation and mineralization are specific to individual soil-biochar combinations and further systematic studies are required to predict agronomic and N cycling responses. Most nitrous oxide (N2O) studies measuring nitrous oxide (N2O) were short-term in nature and found emission reductions, but long-term studies are lacking, as is mechanistic understanding of reductions. Stable N isotopes have a role in elucidating biochar-N-soil dynamics. There remains a dearth of information regarding effects of biochar and soil biota on N cycling. Biochar has potential within agroecosystems to be an N input, and a mitigation agent for environmentally detrimental N losses. Future research needs to systematically understand biochar-N interactions over the long term. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
482 KiB  
Article
Biochar Effect on Maize Yield and Soil Characteristics in Five Conservation Farming Sites in Zambia
by Gerard Cornelissen, Vegard Martinsen, Victor Shitumbanuma, Vanja Alling, Gijs D. Breedveld, David W. Rutherford, Magnus Sparrevik, Sarah E. Hale, Alfred Obia and Jan Mulder
Agronomy 2013, 3(2), 256-274; https://doi.org/10.3390/agronomy3020256 - 11 Apr 2013
Cited by 212 | Viewed by 20913
Abstract
Biochar addition to agricultural soils can improve soil fertility, with the added bonus of climate change mitigation through carbon sequestration. Conservation farming (CF) is precision farming, often combining minimum tillage, crop rotation and residue retention. In the present farmer-led field trials carried out [...] Read more.
Biochar addition to agricultural soils can improve soil fertility, with the added bonus of climate change mitigation through carbon sequestration. Conservation farming (CF) is precision farming, often combining minimum tillage, crop rotation and residue retention. In the present farmer-led field trials carried out in Zambia, the use of a low dosage biochar combined with CF minimum tillage was tested as a way to increase crop yields. Using CF minimum tillage allows the biochar to be applied to the area where most of the plant roots are present and mirrors the fertilizer application in CF practices. The CF practice used comprised manually hoe-dug planting 10-L sized basins, where 10%–12% of the land was tilled. Pilot trials were performed with maize cob biochar and wood biochar on five soils with variable physical/chemical characteristics. At a dosage as low as 4 tons/ha, both biochars had a strong positive effect on maize yields in the coarse white aeolian sand of Kaoma, West-Zambia, with yields of 444% ± 114% (p = 0.06) and 352% ± 139% (p = 0.1) of the fertilized reference plots for maize and wood biochar, respectively. Thus for sandy acidic soils, CF and biochar amendment can be a promising combination for increasing harvest yield. Moderate but non-significant effects on yields were observed for maize and wood biochar in a red sandy clay loam ultisol east of Lusaka, central Zambia (University of Zambia, UNZA, site) with growth of 142% ± 42% (p > 0.2) and 131% ± 62% (p > 0.2) of fertilized reference plots, respectively. For three other soils (acidic and neutral clay loams and silty clay with variable cation exchange capacity, CEC), no significant effects on maize yields were observed (p > 0.2). In laboratory trials, 5% of the two biochars were added to the soil samples in order to study the effect of the biochar on physical and chemical soil characteristics. The large increase in crop yield in Kaoma soil was tentatively explained by a combination of an increased base saturation (from <50% to 60%–100%) and cation exchange capacity (CEC; from 2–3 to 5–9 cmol/kg) and increased plant-available water (from 17% to 21%) as well as water vapor uptake (70 mg/g on maize cob biochar at 50% relative humidity). Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
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