scholarly journals Managing soils for long-term productivity

1997 ◽  
Vol 352 (1356) ◽  
pp. 1011-1021 ◽  
Author(s):  
J. K. Syers
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Biomass ◽  
Soil Fertility ◽  
Organic Material ◽  
Soil Degradation ◽  
Turnover Rate ◽  
Management Practices ◽  
The Tropics

Meeting the goal of long–term agricultural productivity requires that soil degradation be halted and reversed. Soil fertility decline is a key factor in soil degradation and is probably the major cause of declining crop yields. There is evidence that the contribution of declining soil fertility to soil degradation has been underestimated. Sensitivity to soil degradation is implicit in the assessment of the sustainability of land management practices, with wide recognition of the fact that soils vary in their ability to resist change and recover subsequent to stress. The concept of resilience in relation to sustainability requires further elaboration and evaluation. In the context of soil degradation, a decline in soil fertility is primarily interpreted as the depletion of organic matter and plant nutrients. Despite a higher turnover rate of organic matter in the tropics there is no intrinsic difference between the organic matter content of soils from tropical and temperate regions. The level of organic matter in a soil is closely related to the above and below ground inputs. In the absence of adequate organic material inputs and where cultivation is continuous, soil organic matter declines progressively. Maintaining the quantity and quality of soil organic matter should be a guiding principle in developing management practices Soil microbial biomass serves as an important reservoir of nitrogen (N), phosphorus (P) and sulphur (S), and regulates the cycling of organic matter and nutrients. Because of its high turnover rate, microbial biomass reacts quickly to changes in management and is a sensitive indicator for monitoring and predicting changes in soil organic matter. Modelling techniques have been reasonably successful in predicting changes in soil organic matter with different organic material inputs, but there is little information from the tropics. Nutrient depletion through harvested crop components and residue removal, and by leaching and soil erosion accentuates the often very low inherent fertility of many soils in the tropics. An integrated approach involving inorganic and organic inputs is required where animal and plant residues are returned, as far as practicable. Chemical fertilizers alone cannot achieve long–term productivity on many soils and organic material inputs are required to maintain soil organic matter levels and crop productivity. A major research effort is required to develop improved strategies for halting and reversing soil degradation if long–term productivity is to be secured.

Soil organic matter in rainfed cropping systems of the Australian cereal belt

Soil Research ◽  
2001 ◽  
Vol 39 (3) ◽  
pp. 435 ◽  
Author(s):  
R. C. Dalal ◽  
K. Y. Chan
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Management Practices ◽  
Performance Indicator ◽  
Annual Rainfall ◽  
Soil Productivity ◽  
Organic C ◽  
Soil C ◽  
Eastern Australia

The Australian cereal belt stretches as an arc from north-eastern Australia to south-western Australia (24˚S–40˚S and 125˚E–147˚E), with mean annual temperatures from 14˚C (temperate) to 26˚C (subtropical), and with annual rainfall ranging from 250 mm to 1500 mm. The predominant soil types of the cereal belt include Chromosols, Kandosols, Sodosols, and Vertosols, with significant areas of Ferrosols, Kurosols, Podosols, and Dermosols, covering approximately 20 Mha of arable cropping and 21 Mha of ley pastures. Cultivation and cropping has led to a substantial loss of soil organic matter (SOM) from the Australian cereal belt; the long-term SOM loss often exceeds 60% from the top 0–0.1 m depth after 50 years of cereal cropping. Loss of labile components of SOM such as sand-size or particulate SOM, microbial biomass, and mineralisable nitrogen has been even higher, thus resulting in greater loss in soil productivity than that assessed from the loss of total SOM alone. Since SOM is heterogeneous in nature, the significance and functions of its various components are ambiguous. It is essential that the relationship between levels of total SOM or its identif iable components and the most affected soil properties be established and then quantif ied before the concentrations or amounts of SOM and/or its components can be used as a performance indicator. There is also a need for experimentally verifiable soil organic C pools in modelling the dynamics and management of SOM. Furthermore, the interaction of environmental pollutants added to soil, soil microbial biodiversity, and SOM is poorly understood and therefore requires further study. Biophysically appropriate and cost-effective management practices for cereal cropping lands are required for restoring and maintaining organic matter for sustainable agriculture and restoration of degraded lands. The additional benefit of SOM restoration will be an increase in the long-term greenhouse C sink, which has the potentialto reduce greenhouse emissions by about 50 Mt CO2 equivalents/year over a 20-year period, although current improved agricultural practices can only sequester an estimated 23% of the potential soil C sink.

Long-term effects of NPK fertiliser and manure on soil fertility and a sorghum - wheat farming system

2007 ◽  
Vol 47 (6) ◽  
pp. 700 ◽  
Author(s):  
M. C. Manna ◽  
A. Swarup ◽  
R. H. Wanjari ◽  
H. N. Ravankar
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Soil Organic Matter ◽  
Microbial Biomass ◽  
Aggregate Size ◽  
Microbial Biomass C ◽  
Continuous Cropping ◽  
C And N ◽  
Organic Matter Fractions

Yield decline or stagnation under long-term cultivation and its relationship with soil organic matter fractions are rarely considered. To understand this phenomenon, soil organic matter fractions and soil aggregate size distribution were studied in a long-term experiment at Akola, in a Vertisol in a semiarid tropical environment. For 14 years, the following fertiliser treatments were compared with undisturbed fallow plots: unfertilised (control), 100% recommended rates of N, NP, NPK (N : P : K ratios of 100 : 21.8 : 18.2 and 120 : 26.2 : 50 kg/ha for sorghum and wheat, respectively) and 100% NPK plus farmyard manure (FYM) and continuous cropping with a sorghum (Sorghum bicolor L. Moench) and wheat (Triticum aestivum L.) system during 1988–2001. The significant negative yield trend was observed in unbalanced use of inorganic N application for both crops. However, yields were maintained when NPK and NPK + FYM were applied. Results showed that soil organic C and total N in the unfertilised plot decreased by 21.7 and 18.2%, compared to the initial value, at a depth of 0–15 cm. Depletion of large macroaggregates (>2 mm) accounted for 22–81% of the total mass of aggregates in N, NP and unfertilised control plots compared to fallow plots. Irrespective of treatments, small macroaggregates (0.25–2 mm) dominated aggregate size distribution (56–71%), followed by microaggregates (0.053–0.25 mm, 18–37%). Active fractions, such as microbial biomass C, microbial biomass N, hot water soluble C and N, and acid hydrolysable carbohydrates were greater in NPK and NPK + FYM treatments than in the control. Carbon and N mineralisation were greater in small macroaggregates than microaggregates. Particulate organic matter C (POMC) and N (POMN) were significantly correlated (P < 0.01) with water-stable aggregate C and N (0.25–2 mm size classes), respectively. It was further observed that POMC and POMN were significantly greater in NPK and NPK + FYM plots than N and NP treated plots. Microbial biomass C was positively correlated with acid-hydrolysable carbohydrates (r = 0.79, P < 0.05). Continuous cropping and fertiliser use also influenced humic acid C and fulvic acid C fractions of the soil organic matter. Acid-hydrolysable N proportion in humic acid was greater than fulvic acid and it was greatest in NPK + FYM treatments. Continuous application of 100% NPK + FYM could restore soil organic carbon (SOC) to a new equilibrium level much earlier (t = 1/k, 2.4 years) than N (t = 1/k, 25.7 years), NP (t = 1/k, 8.1 years) and NPK (t = 1/k, 5.02 years). In conclusion, integrated use of NPK with FYM would be vital to obtain sustainable yields without deteriorating soil quality.

Modelling dynamic interactions between soil structure and soil organic matter

2020 ◽  
Author(s):  
Nicholas Jarvis ◽  
Elsa Coucheney ◽  
Claire Chenu ◽  
Anke Herrmann ◽  
Thomas Keller ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Sequestration ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Physical Properties ◽  
Management Practices ◽  
Animal Manure ◽  
Soil Bulk Density ◽  
Organic Carbon Content

&lt;p&gt;The aggregated structure of soil is known to reduce rates of soil organic matter (SOM) decomposition and therefore influence the potential for long-term carbon sequestration. In turn, the storage and turnover of SOM strongly determines soil aggregation and thus the physical properties of soil. The two-way nature of these interactions has not yet been explicitly considered in soil organic matter models. In this study, we present and describe a new model of these dynamic feedbacks between SOM storage, soil pore structure and soil physical properties. We show the results of a test of the model against measurements made during 61 years in a field trial located near Uppsala (Sweden) in two treatments with different OM inputs (bare fallow, animal manure). The model was able to successfully reproduce long-term trends in soil bulk density and organic carbon content (SOC), as well as match limited data on soil pore size distribution and surface elevation. The results suggest that the model approach presented here could prove useful in analyses of the effects of soil and crop management practices and climate change on the long-term potential for soil organic carbon sequestration.&lt;/p&gt;

scholarly journals Soil properties and not inputs control carbon : nitrogen : phosphorus ratios in cropped soils in the long term

SOIL ◽  
2016 ◽  
Vol 2 (1) ◽  
pp. 83-99 ◽  
Author(s):  
Emmanuel Frossard ◽  
Nina Buchmann ◽  
Else K. Bünemann ◽  
Delwende I. Kiba ◽  
François Lompo ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Biomass ◽  
Soil Properties ◽  
Nutrient Concentrations ◽  
Nutrient Ratios ◽  
Plant Residues ◽  
Wagga Wagga ◽  
Positive Correlation

Abstract. Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies have explicitly considered the effects of agricultural management practices on the soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long term. Thus, we analysed the C, N, and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK (bio-Dynamic, bio-Organic, and “Konventionell”) cropping system trial (Switzerland). In each of these trials, there was a large range of C, N, and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P, and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure, and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and nutrients, and has a stable structure. Thus, organic matter is protected from mineralization and can therefore accumulate, allowing microorganisms to feed on soil nutrients and to keep a constant C : N : P ratio. The DOK soil represents an intermediate situation, with high nutrient concentrations, but a rather fragile soil structure, where organic matter does not accumulate. We conclude that the study of C, N, and P ratios is important to understand the functioning of cropped soils in the long term, but that it must be coupled with a precise assessment of element inputs and budgets in the system and a good understanding of the ability of soils to stabilize C, N, and P compounds.

The role of long-term sites in agroecological research: A case study

1995 ◽  
Vol 75 (1) ◽  
pp. 123-133 ◽  
Author(s):  
H. H. Janzen
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Management Practices ◽  
Cropping Systems ◽  
Simulation Models ◽  
Sample Collection ◽  
Productivity Measurement ◽  
Sampling Protocols ◽  
Long Term Studies

Gradual, episodic or subtle changes in agroecosystems can be definitively measured only in long-term studies. The objective of this paper is to illustrate the benefits and limitations of long-term agroecological sites using a crop rotation study (Rotation ABC) established at Lethbridge, Alberta in 1910. Long-term agroecological sites, envisioned as part of a continuum of research levels, seek to determine the persistence of cropping systems with respect to their effects on soil resources and the larger environment. Examples of research findings arising from such sites include the documentation of long-term changes in agricultural productivity, measurement of organic matter changes over time, calculation of long-term nutrient budgets, and verification of simulation models. For example, soil organic matter concentrations in Rotation ABC were found to decline abruptly within the first few decades of cultivation and then approach a new steady state. Despite the continual removal of N in harvested grain, soil N concentrations also appear to have stabilized, suggesting an accession of N approximately equivalent to the amount harvested. Common limitations of long-term sites like that at Lethbridge include: rudimentary experimental design, evolving management practices, incidental changes at the sites, and variation in sampling protocols. The successful use of long-term agroecological sites depends on well-defined objectives, simplicity of design, adequate scale, consistent data and sample collection, and collaboration among sites. The primary justification for the establishment and maintenance of long-term agroecological sites may be their future role in answering questions not yet envisioned. Key words: Soil organic matter, long-term studies, crop rotations, sustainability, fertilizer

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