Non-inverting Tillage: Early-Stage Effects on Soil Mechanical Behaviour

Organic farmers often claim positive effects of non-inverting and reduced tillage systems. There is a need of quantifying tilth characteristics in the former plough layer of soil converted to such tillage systems. A non-inverting tillage system (NINV) was tested in a field experiment conducted on a Danish sandy loam soil. It included deep loosening and shallow intensive cultivation and was compared to a conventional ploughing-harrowing tillage system (CONV). A hierarchical analytical procedure was applied in studies of soil fragmentation and soil strength characteristics for the 7-14 cm soil layer. A visual description was carried out and ease of fragmentation was evaluated in the field using a soil drop test. Soil strength was measured in the field with a cone penetrometer and a torsional shear box method, and in the laboratory using an annulus shear strength method. Tensile strength was determined in the laboratory on field-sampled aggregates. The CONV treated soil displayed a higher ease of fragmentation in the field in May as well as in September. In general, aggregates from the NINV treated soil were stronger than aggregates from the CONV treatment. The soils had similar friability indices in May. In September, however, a higher friability index was found for the CONV treated soil (k=0.22 and 0.16, respectively for CONV and NINV). The NINV treated soil also displayed the highest soil strength. The soil tilth was evaluated to be best in the CONV treated soil. Supposed meliorating actions during the growing season did not eliminate the differences between the treatments

Biotic and abiotic binding and bonding mechanisms in soils with long-term differences in management

During the last decades Denmark has experienced a growing interest in low-input farming systems like organic farming. These systems rely on a high soil fertility to maintain nutrient availability and plant health. Soil aggregation contributes to this fertility, because it is crucial to soil porosity, aeration and infiltration of water. This paper reports a study of two pairs of differently managed, neighboring fields. The aim was to elucidate long-term effects of the different farming systems on physical and biological variables with influence on bonding and binding mechanisms of soil aggregation. Each pair consists of an organically grown dairy farm soil, based on a forage crop rotation system, including grass (Org-FCS(G)) and a conventionally managed soil. One of the conventional farms has a forage crop rotation with annual cash crops and no grass (Conv-FCS(NG)) and one has been grown continuously with small grain cereals and rape (Conv-CCS). Our results indicate that the Org-FCS(G) soils stimulate biotic soil aggregating agents as measured by extracellular polysaccharides (EPS) and hyphal length measurements, respectively. Generally, the Conv-CCS soil, which relies exclusively on synthetic fertilisers and cereal production, offered poor conditions for the biotic binding and bonding agents. Nevertheless this soil contained a large amount of stable macro-aggregates. This is explained by the physical results, which indicated that the strong macro-aggregation was due to clay dispersion and cementation processes rather than to biotic processes

Multi-level assessment of soil quality – linking reductionistic and holistic methodologies

Soil quality is often used as a qualitative, general term. However, quantification is an important feature of the scientific approach to nature. On the other hand, addressing specific soil parameters as indicators of soil quality includes a reduction of the whole soil system. Therefore, results obtained by specialized methodologies ought to be evaluated by methods integrating the soil characteristics in situ. In this presentation, results are given from an investigation of the tilth of two differently managed loamy soils. One of the soils had been managed for decades with a forage crop system (labeled FCS), which included fertilization with farmyard manure, while the other had been grown with a continuous cereal system (labeled CCS), receiving no input of organic matter. In the field, the structure of the top 30-cm soil layer was described visually (spade analysis) and by studying the fragmentation behavior (soil drop test). Further, the field measurements included determination of soil strength by a torsional shear box method. In the laboratory, shear strength was determined on bulk soil sampled in metal cylinders, and tensile strength was estimated from crushing tests of individual, differently sized aggregates. The FCS soil appeared porous, with crumbs as structural units, while the CCS soil was compact with blocks as structural units. The soil drop test yielded the highest degree of fragmentation for the FCS soil. The torsional shear box method showed the CCS soil to have the highest bulk soil strength. This was confirmed by the laboratory shear annulus method. Finally, the tensile strength measurements revealed a much higher strength of 8-16, 4-8 and 2-4 mm dry aggregates from the CCS soil as compared to the FCS soil, while 1-2 mm aggregates were strongest in the FCS soil. This indicates a higher friability for the FCS soil, which is in accordance with the soil behavior in the field tests. In conclusion, the quality of the FCS soil – as evaluated by its mechanical behavior – was found to be higher than that of the CCS soil. An important result is the good correlation between the integrating field methods and the differentiating laboratory methods. This means that the quantifying, reductionistic scientific approach is not conflicting with the ‘holistic’ descriptions in the field

Afgrøderester og sædskifte har stor betydning for udledning af lattergas

Lattergas udgør en del af det atmosfæriske tab af kvælstof fra dyrkningsjorden. Målt i kg kvælstof er mængderne små, men fordi lattergas er en meget kraftig drivhusgas, er gassens betydning for landbrugets samlede udledninger stor

Jordbearbejdning i økologisk jordbrug – pløjedybde og ikke-vendende jordløsning [Soil tillage in organic farming – ploughing depth and non-inversion deep tillage]

I perioden 1996 til 2000 gennemførtes et markforsøg med forskellige jordbearbejdnings-systemer på Den økologiske Forsøgsstation Rugballegaard. Forsøgsarealet blev omlagt til økologisk drift i forbindelse med projektets start i 1996. Undersøgelserne gennemførtes i et fem-marks skifte, der ligeledes blev kørt ind i forbindelse med projektet. Det drejer sig om et såkaldt blandet sædskifte med byg/ært m. udlæg, 1. års kløvergræs, 2. års kløvergræs, havre og vinterhvede. Forsøget blev anlagt i fem marker (B1-B5), hvilket indebærer, at alle skiftets afgrøder blev dyrket hvert år. Fire forskellige jordbearbejdningssystemer blev undersøgt i et randomiseret blokforsøg med 4 blokke. De fire behandlinger omfattede to systemer med pløjning, nemlig led A med 20 cm pløjedybde og led B med 10-12 cm pløjedybde; hertil kom to systemer (C og D) med ikke-vendende løsning af jorden til 35-40 cm dybde. Til dette formål blev opbygget et specielt ud-styr i forbindelse med projektet. Der blev dog anvendt kommercielt tilgængelige gåsefod-stænder fra det tyske firma Dutzi. Disse blev monteret på en svær bulle, der også gav mulig-hed for ophængning af en Howard tandfræser. På denne var der monteret løftehitch, hvori en konventionel Nordsten slæbeskær-såmaskine kunne monteres. Forsøgsled C (’fuld’ Dutzi) omfattede en bearbejdning med hele denne ’ekvipage’ i én arbejdsgang, mens der i led D (’delt’ Dutzi) blev gennemført en separat bearbejdning med Dutzi-tænderne efterfulgt af så-ning med tandfræser og såmaskine. Omlægning af græsmarken skete for alle systemer med traditionel pløjning til 20 cm dybde. Anvendelsen af Dutzi-udstyret krævede meget stor trækkraft og der var ikke nævneværdig mindskelse af dette ved at anvende løsnetænderne separat. Jordløsningen var i både C og D meget effektiv og gav anledning til en markant mindskelse af den mekaniske modstand i jordlaget fra ca. 20 til ca. 35 cm dybde, hvor der på arealet generelt fandtes en kompakt pløje-sål. Effekten på den mekaniske modstand i jorden viste sig at vedvare i minimum 2 år. Den ændrede jordfysiske tilstand gav forbedrede betingelser for bl.a. rodvækst og knoldbakterier (Rhizobium). De undersøgte bearbejdningsmetoder gav ikke entydige ændringer i ukrudtstrykket. Generelt (for alle bearbejdninger) var der problemer med at styre ukrudtet i vinterhveden. En tendens til forøget ukrudtstryk i udlægsmarken efter Dutzi-behandling i forhold til pløjning gav ikke øgede problemer, idet forskellen udlignede sig ved høst af dæksæden som helsæd. Der var heller ikke entydige tendenser i bearbejdningernes indflydelse på udbyttet af afgrøderne. Der var en tendens til, at Dutzi-løsning gav et lidt højere råprotein-indhold i helsæds- og kløver-græsudbyttet end pløjning. Både Dutzi-bearbejdningen og den overfladiske pløjning må betragtes som realistiske mulig-heder i et økologisk sædskifte som det undersøgte. En sikker konklusion om systemernes suc-ces vil kræve undersøgelser gennem mere end en rotation. Desuden kan resultaterne tænkes at være anderledes i andre sædskifter. Ploven vil fortsat være nødvendig i mange økologiske jordbrug p.g.a. behovet for at nedmulde flerårige afgrøder og halm-rig staldgødning mm. I stedet for fuld overgang til ikke-vendende jordløsning, forekommer det realistisk at reducere pløjedybden til det mindst mulige og fore-tage en evt. påkrævet mekanisk løsning af dybere jordlag med maskinel, der bryder jorden op til den ønskede dybde uden at vende den. Her er Dutzi-tænderne (separat eller i forbindelse med et kombisæt) én af flere muligheder. Der bør gennemføres forsøgsserier på forskellige jordtyper, hvor forskellige systemer testes med henblik på optimering af jordstruktur og biodiversitet i jorden, udbyttets størrelse og kvalitet, ukrudtsbekæmpelse samt med henblik på minimering af arbejdstid og forbrug af fos-silt brændstof. Sådanne undersøgelser bør dække de vigtigste kombinationer af jordtype, sæd-skifte og gødskningsstrategi mm. og gennemføres i så langt et tidsrum, at det er muligt at vur-dere de nævnte succeskriterier efter en nødvendig overgangsfase

Long-term effects of cropping system on N2O emission potential

The potential for N2O emissions outside the main growing season may be influenced by long-term effects of cropping system. This was investigated by collecting intact soil cores (100 cm3, 0-4 cm depth) under winter wheat in three organic cropping systems and a conventional reference within a long-term crop rotation experiment. Average annual inputs of C in crop residues and manure ranged from 1.7 to 3.3 Mg ha-1. A simulated freeze-thaw cycle resulted in a flush of CO2 during the first 48 h, which could be mainly from microbial sources. Other samples were adjusted to approximately –10, -30 or –100 hPa and amended with excess 15NO3- prior to freezing and thawing. Denitrification was the main source of N2O during a 72-h incubation at 22C, as judged from N2O and total 15N evolution. Although the input of C in the conventionally managed cropping system was significantly less than in the organic cropping systems, it showed higher N2O evolution at all three matric potentials. Estimates of relative gas diffusivity (DP/D0) in soil from the four cropping systems indicated that C input affected soil aeration. Soil from the two cropping systems with highest C input showed N2O evolution at DP/D0 in excess of 0.02, which is normally considered a threshold for development of anaerobic sites in the soil, presumably because the oxygen demand was also high. The study shows that cropping system affects both soil gas diffusivity and C availability, and that both characteristics significantly influence the N2O emission potential

Sources of nitrogen for winter wheat in organic cropping systems

In organic cropping systems, legumes, cover crops, residue incorporation, and manure application are used to maintain soil fertility, but the contributions of these management practices to soil nitrogen (N) supply remain obscure. We examined potential sources of N for winter wheat (Triticum aestivum L.) in four experimental cropping systems established in 1997 on three soil types. Three of the four systems were under organic management. Topsoil N, depth of the A horizon, and cumulated inputs of N since 1997 were determined at plot level. Labile soil N pools (mineral N, potentially mineralizable N [PMN], microbial biomass N [MBN]) were monitored during two growth periods; at one site, biomass C/N ratios were also determined. Soil for labile N analysis was shielded from N inputs during spring application to isolate cumulated system effects. PMN and MBN were correlated across all sites and rotations (r2=0.72). The MBN corresponded to 46-85, 85-145 and 74-172 kg N ha-1 at the three sites and differed significantly between cropping systems, but MBN could not explain differences in wheat grain N yields. Instead, a multiple linear regression model explained 76 and 82% of the variation in grain N yields in organic cropping systems in 2007 and 2008, showing significant effects of, respectively, topsoil N, depth of A horizon, cumulated inputs of N, and N applied to winter wheat in manure. Thus, soil properties, and past and current management all contributed to winter wheat N supply

Terranimo® – ein webbasiertes Modell zur Abschätzung des Bodenverdichtungsrisikos

Um die Druckverhältnisse unter Landmaschinen zu simulieren und das Bodenverdichtungsrisiko einschätzen zu können, wurde das webbasierte Modell Terranimo® entwickelt. Darin kann mithilfe von verfügbaren Reifenkennwerten und in Abhängigkeit von der Oberbodenfestigkeit die Kontaktfläche und die Druckverteilung zwischen Reifen und Boden beschrieben werden. Mithilfe von Pedotransferfunktionen wird die Bodenfestigkeit (Vorbelastung) vom Tongehalt und der Saugspannung im Boden abgeleitet. Das Verdichtungsrisiko wird durch den Vergleich von Bodenfestigkeit und ausgeübtem Bodendruck abgeschätzt: Bleibt der durch die Landmaschine ausgeübte Bodendruck unterhalb der aktuellen Bodenfestigkeit, so können das Verdichtungsrisiko minimiert und negative Veränderungen der Bodenstruktur – und somit der Bodenfunktionen – vermieden werden.Based on experimental data from wheeling experiments, a web-based model for the simulation of stress and the evaluation of the soil compaction risk under agricultural machinery named Terranimo® has been developed. Terranimo® incorporates a model for prediction of contact area, shape and stress distribution in the tyre soil interface from wheel load and readily-available tyre parameters and the topsoil strength. In Terranimo® pedotransfer functions are used to estimate soil strength from clay content and matric potential. Principally, by limiting the imposed stress to below soil strength, the risk of soil compaction and undesirable changes of soil structure – and hence soil functions – can be minimized

Bæredygtig trafik i marken

Titlen kan lyde som en vittighed: jorden skal bære trafikken,- den skal være bæredygtig. Men driftsmetoder, der skader jorden vedvarende er ikke bæredygtige. Og nutidens maskiner giver skader. Man kunne også stille spørgsmålet, om man kan tale om ”økologisk trafik”? Økologerne har været foregangsmænd/-kvinder hvad angår udfasning af pesticider og mineralsk gødning. Budskabet i denne artikel er, at der ligger en tilsvarende udfordring og venter mht vores trafik i marken