Jutta Rogasik

Assessing the productivity function of soils. A review

The development and survival or disappearance of civilizations has been based on the performance of soils to provide food, fibre, and further essential goods for humans. Amongst soil functions, the capacity to produce plant biomass (productivity function) remains essential. This function is closely associated with the main global issues of the 21st century like food security, demands of energy and water, carbon balance and climate change. A standardised methodology for assessing the productivity function of the global soil resource consistently over different spatial scales will be demanded by a growing international community of land users and stakeholders for achieving high soil productivity in the context of sustainable multifunctional use of soils. We analysed available methods for assessing the soil productivity function. The aim was to find potentials, deficiencies and gaps in knowledge of current approaches towards a global reference framework. Our main findings were (i) that the soil moisture and thermal regime, which are climate-influenced, are the main constraints to the soil productivity potential on a global scale, and (ii) that most taxonomic soil classification systems including the World Reference Basis for Soil Resources provide little information on soil functionality in particular the productivity function. We found (iii) a multitude of approaches developed at the national and local scale in the last century for assessing mainly specific aspects of potential soil and land productivity. Their soil data inputs differ, evaluation ratings are not transferable and thus not applicable in international and global studies. At an international level or global scale, methods like agro-ecological zoning or ecosystem and crop modelling provide assessments of land productivity but contain little soil information. Those methods are not intended for field scale application to detect main soil constraints and thereby to derive soil management and conservation recommendations in situ. We found also, that (iv) soil structure is a crucial criterion of agricultural soil quality and methods of visual soil assessment like the Peerlkamp scheme, the French method “Le profil cultural” and the New Zealand Visual Soil Assessment are powerful tools for recognising dynamic agricultural soil quality and controlling soil management processes at field scale. We concluded that these approaches have potential to be integrated into an internationally applicable assessment framework of the soil’s productivity function, working from field scale to the global level. This framework needs to serve as a reference base for ranking soil productivity potentials on a global scale and as an operational tool for controlling further soil degradation and desertification. Methods like the multi-indicator-based Muencheberg Soil Quality Rating meet most criteria of such a framework. This method has potential to act as a global overall assessment method of the soil productivity function for cropping land and pastoral grassland but needs further evolution by testing and amending its indicator thresholds.

Effect of mineral and organic fertilization on crop yield, nitrogen uptake, carbon and nitrogen balances, as well as soil organic carbon content and dynamics: results from 20 European long-term field experiments of the twenty-first century

Assembled results from 20 European long-term experiments (LTE), mainly from the first decade of the twenty-first century, are presented. The included LTEs from 17 sites are the responsibility of institutional members of the International Working Group of Long-term Experiments in the IUSS. Between the sites, average annual temperatures differ between 8.1 and 15.3°C, annual precipitation between 450 and 1400 mm, and soil clay contents between 3 and 31%. On average of 350 yield comparisons, combined mineral and organic fertilization resulted in a 6% yield benefit compared with mineral fertilization alone; in the case of winter wheat, the smallest effect was 3%, the largest effect, seen with potatoes, was 9%. All unfertilized treatments are depleted in soil organic carbon (SOC), varying between 0.36 and 2.06% SOC. The differences in SOC in unfertilized plots compared with the respective plots with combined mineral (NPK) and organic (10 t ha−1 farmyard manure) fertilization range between 0.11 and 0.72%, with an average of 0.3% (corresponding to ∼15 t ha−1). Consequently, the use of arable soils for carbon sequestration is limited and of low relevance and merely depleted soils can temporarily accumulate carbon up to their optimum C content.

Assessing the Productivity Function of Soils

The development and survival or disappearance of civilizations has been based on the performance of soils to provide food, fibre, and further essential goods for humans. Amongst soil functions, the capacity to produce plant biomass (productivity function) remains essential. This function is closely associated with the main global issues of the 21st century like food security, demands of energy and water, carbon balance and climate change. A standardised methodology for assessing the productivity function of the global soil resource consistently over different spatial scales will be demanded by a growing international community of land users and stakeholders for achieving high soil productivity in the context of sustainable multifunctional use of soils. We analysed available methods for assessing the soil productivity function. The aim was to find potentials, deficiencies and gaps in knowledge of current approaches towards a global reference framework. Our main findings were (i) that the soil moisture and thermal regime, which are climate-influenced, are the main constraints to the soil productivity potential on a global scale, and (ii) that most taxonomic soil classification systems including the World Reference Basis for Soil Resources provide little information on soil functionality in particular the productivity function. We found (iii) a multitude of approaches developed at the national and local scale in the last century for assessing mainly specific aspects of potential soil and land productivity. Their soil data inputs differ, evaluation ratings are not transferable and thus not applicable in international and global studies. At an international level or global scale, methods like agro-ecological zoning or ecosystem and crop modelling provide assessments of land productivity but contain little soil information. Those methods are not intended for field scale application to detect main soil constraints and thereby to derive soil management and conservation recommendations in situ. We found also that (iv) soil structure is a crucial criterion of agricultural soil quality and methods of visual soil assessment like the Peerlkamp scheme, the French method “Le profil cultural” and the New Zealand Visual Soil Assessment are powerful tools for recognising dynamic agricultural soil quality and controlling soil management processes at field scale. We concluded that these approaches have potential to be integrated into an internationally applicable assessment framework of the soil’s productivity function, working from field scale to the global level. This framework needs to serve as a reference base for ranking soil productivity potentials on a global scale and as an operational tool for controlling further soil degradation and desertification. Methods like the multi-indicator-based Muencheberg Soil Quality Rating meet most criteria of such a framework. This method has potential to act as a global overall assessment method of the soil productivity function for cropping land and pastoral grassland but needs further evolution by testing and amending its indicator thresholds.

Long-term fertilizer experiments as a data base for calculating the carbon sink potential of arable soils

Long-term experiments in Müncheberg, Braunschweig and Livada were used to understand the complex issue of carbon sequestration in soil. The investigations were focused on: effects of land use changes on the fate of soil organic carbon; options of agronomic practices to maintain or to increase soil organic carbon; relationships between organic fertilization and changes in soil organic carbon. The long-term observations showed that the amount of soil organic matter is primarily a function of the prevailing land use. Clearly marked differences were observed between long-term arable farming with lower and short-term with higher soil organic carbon content. Agricultural practices lead to a decrease of soil organic carbon with the result that arable soils are rather sources of carbon than sinks. The carbon sequestration potential is caused by the agronomic management to different extents. The combination of organic and mineral fertilization increased the soil organic carbon content compared to exclusive mineral fertilization. Optimum values of organic fertilizer application for maintaining soil organic carbon were calculated. Liming reduced the soil carbon pool when applied in large amounts. Long-term fertilization experiments are a useful tool for calculating the carbon sink or source potential of arable soils.

A framework for assessing agricultural soil quality on a global scale

This paper provides information about a novel approach of rating agricultural soil quality (SQ) and crop yield potentials consistently over a range of spatial scales. The Muencheberg Soil Quality Rating is an indicator-based straightforward overall assessment method of agricultural SQ. It is a framework covering aspects of soil texture, structure, topography and climate which is based on 8 basic indicators and more than 12 hazard indicators. Ratings are performed by visual methods of soil evaluation. A field manual is then used to provide ratings from tables based on indicator thresholds. Finally, overall rating scores are given, ranging from 0 (worst) to 100 (best) to characterise crop yield potentials. The current approach is valid for grassland and cropland. Field tests in several countries confirmed the practicability and reliability of the method. At field scale, soil structure is a crucial, management induced criterion of agricultural SQ. At the global scale, climate controlled hazard indicators of drought risk and soil thermal regime are crucial for SQ and crop yield potentials. Final rating scores are well correlated with crop yields. We conclude that this system could be evolved for ranking and controlling agricultural SQ on a global scale.

Humus und Klimaänderung - Ergebnisse aus 15 langjährigen Dauerfeldversuchen

Zusammenfassung Die Quantifizierung des Einflusses von Klimaänderungen auf den Humusgehalt des Bodens ist von großer wirtschaftlicher und wissenschaftlicher Bedeutung. Eine Möglichkeit dieser Quantifizierung besteht in der Auswertung von Dauerfeldversuchen mit der kontinuierlichen Bestimmung des Kohlenstoff- und Stickstoffgehaltes von Böden über einen Zeitraum von mehreren Jahrzehnten unter Wahrung des Ceteris-Paribus-Prinzips. Für die vorliegende Arbeit wurden die Ergebnisse von insgesamt 15 Dauerfeldversuchen an zehn verschiedenen Standorten mit rund 150 unterschiedlichen Düngungsvarianten ausgewertet. Die Versuchsdauer lag mit einer Ausnahme zwischen 40 und 110 Jahren. Die Corg-Daten konnten nahezu lückenlos über einen Zeitraum von jeweils 20 Jahren einbezogen werden. Die Nt-Gehalte wurden in sechs Versuchen berücksichtigt. Die Ergebnisse zeigen, dass bei allen Prüfgliedern mit kombinierter organisch-mineralischer Düngung in der Größenordnung, wie sie der “guten fachlichen Praxis“ oder auch der Humusbilanzmethode entspricht, keine Verringerung der Corg-Gehalte eingetreten ist. In einigen Fällen waren signifikante Erhöhungen zu verzeichnen. In 11 von 15 Versuchen war auch ohne Düngung oder mit ausschließlicher Mineraldüngung keine Reduzierung und somit keine klimabedingte Verringerung der Humusgehalte im Untersuchungszeitraum nachweisbar. Stattdessen wurde in einigen Fällen eine signifikante Erhöhung gefunden. Auch bei den Nt-Gehalten war in keinem Fall eine signifikante Verringerung festzustellen. Umfangreiche Großzahlanalysen und Dauerfeldversuchsauswertungen anderer Autoren bestätigen uneingeschränkt die Ergebnisse.

Langzeiteffekte ackerbaulicher massnahmen auf die bodenfruchtbarkeit

An Hand von Dauerversuchen in Braunschweig und Müncheberg wird in einer Fallstudie der Einfluß landbaulichen Managements auf Erträge und Bodenfruchtbarkeit dargestellt. Langfristig werden hohe Erträge sowie optimale Humusgehalte nur durch kombinierte organisch ‐ mineralische Düngung erreicht. In den Varianten hoher Erträge finden sich vergleichsweise höhere Bodengehalte an Corg, P(CAL) sowie höhere pH‐Werte. Ohne organische Düngung (Variante NPK) kann der Corg‐Gehalt des Bodens nicht aufrechterhalten werden. Doch auch alleinige organische Düngung (Variante Stm2) reicht auf sandigen Ackerstandorten nicht aus, optimale Humusgehalte einzustellen. Langfristig erhöht konservierende Bodenbearbeitung die Erträge und verringert die N‐Austräge in die Atmosphäre und ins Grundwasser.

Faktoreinsatz in der landwirtschaft ‐ein beitrag zur ressourcenschonung (Daten und analysen aus dem müncheberger nährstoff‐steigerungsversuch)

Dargestellt werden ausgewahlte Ergebnisse des Muncheberger Nahrstoffsteigerungsversuches unter dem Aspekt des Ressourcenschutzes ‐ Energie, Boden, Wasser und Luft. EnergielCO, : Durch den verantwortungsvollen Faktoreinsatz in der Landwirtschaft (mineralische und organische Dungemittel, Treib‐ und Schmierstoffe) kann der Energieeinsatz und damit die CO2‐Emission im Vorleistungsbereich der Landwirtschaft reduziert werden. Boden: Die Untersuchungen haben gezeigt, das kombinierte organisch‐mineralische Dungung eine wesentliche Masnahme ist, optimale Humusgehalte im Boden zu sichern. Menge und Qualitat der organischen Bodensubstanz werden durch das Management beeinflust. Luft, Wasser: Die Hohe der Dungung beeinflust uber die NO3‐Konzentration im Boden entscheidend die N2O‐Abgaberaten in die Atmosphare bzw. Nitrataustrage ins Grundwasser. Erfolgreiche N2O‐Vermeidungsstrategien sind in Managementmasnahmen zu sehen, die ein optimales Pflanzenwachstum gewahrleisten und N‐Verluste aus dem System Boden‐Pflanze verhi...

Landbau und treibhauseffekt‐quellen und senken für CO2 bei unterschiedlicher landbewirtschaftung

Die Ergebnisse der Müncheberger Dauerversuche sind eine geeignete Datenbasis zur Bewertung der CO2‐Senke im Landbau (produzierter Gesamtertrag und Akkumulation von organischer Bodensubstanz) sowie der CO2‐Quelle (Verlust an organischer Bodensubstanz und Einsatz fossiler Energie). Durch diese Parameter sind wesentliche Größen für die Quantifizierung des C‐ bzw. CO2‐Haushaltes gegeben. Sie sind Indikatoren für den Vergleich unterschiedlicher Bewirtschaftungsintensitäten und charakterisieren die Umweltverträglichkeit der Pflanzenproduktion. Ein reduzierter Faktoreinsatz kann die CO2‐Emission im Vorleistungsbereich der Landwirtschaft nur dann mindern, wenn dieser geringere Faktoreinsatz nicht mit deutlich geringerem Energiegewinn (CO2‐Bindung im Ernteertrag) verbunden ist. Ziel landwirtschaftlicher Bodennutzung ist es u.a., die Erhaltung standorttypischer C‐Gehalte im Boden zu gewährleisten. Langfristig kann durch kombinierte organischmineralische Düngung sowie konservierende Bodenbearbeitungsverfahren auf sandigen Böden eine Erhöhung des C‐Pools im Boden um ca. 10% erreicht werden. Die CO2‐Emissionen im Vorleistungsbereich der Landwirtschaft sollten auf sandigen Ackerstandorten 9 bis 10% der in der Biomasse gespeicherten CO2‐Menge nicht übersteigen.

On-farm study of reduced tillage on sandy soil: effects on soil organic carbon dynamic and earthworm abundance

Information about the long-term effects of reduced soil tillage on soil fertility of sandy soils under dry climatic conditions is scarce. Soil organic carbon and earthworm populations were evaluated as soil fertility indicators in an on-farm study between 1996 and 2008. The study comprised adjacent conventional and reduced tillage treatments, undertaken at field (74 ha) scale in Northeast Brandenburg, Germany, with a total of 42 plots on heterogeneous sandy loam. The soil is classified as a Luvisol. Organic carbon stocks at 0–30 cm depth increased between 1996 and 2008 in both tillage systems. This increase corresponded to predictions obtained with the humus balance method based on crop rotation and yields. Increases of organic carbon stocks were slightly more pronounced in plots under reduced tillage. Earthworm population numbers determined by handsorting at 42 plots, were higher in plots under reduced tillage compared to conventional tillage, mainly due to the occurrence of Lumbricus terrestris. The results indicate that reduced tillage systems provide a suitable crop production strategy for maintaining soil fertility on sandy soils under dry climatic conditions.