G. Kirchhof

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Papers by G. Kirchhof

Soil & Tillage Research

Leucaena as an opportunity for recharge management in northern Australia: Fitzroy Basin case study

Soil fertility assessment of soils in the highlands of Papua New Guinea

Management of Clay Soils for Lowland Rice-based Cropping Systems: An Overview of ACIAR Project 8938

Statistical methods for a soil fertility management survey analysis in Papua New Guinea

ABSTRACT This paper is a short communication about methods used in the analysis of biophysical da... more ABSTRACT This paper is a short communication about methods used in the analysis of biophysical data from the scoping stage of a soil fertility management survey in Papua New Guinea conducted in September–October 2005 (Australian Centre for International Agricultural Research project SMCN/2005/043). The goal of this communication is to describe and promote the good practice of statistics in application to biophysical surveys. A step-by-step analysis is presented of the difference in sweetpotato yield between newly established gardens and gardens that have been cultivated for a long period. We comment on the strengths and limitations of statistical techniques used in the analysis, and also relate the techniques to the corresponding software procedures (R15, Minitab Inc., Chicago). Although we refer to various general methods, the analysis presented is specific to one particular survey. This paper may be useful for agricultural researchers as a case study of the data analysis of field surveys in research or extension projects

Digestibility of starch and potassium in sweetpotato from Papua New Guinea

Potassium is a major mineral in sweetpotato, and like most root crops, sweetpotato has high starc... more Potassium is a major mineral in sweetpotato, and like most root crops, sweetpotato has high starch content. There are many cultivars of sweetpotato with genotype and environmental differences, which influence digestibility and bioavailability. Starch and mineral digestibility in food materials are currently topical because of associated nutritional implications. Time-course in-vitro starch and potassium digestibility of 20 samples of sweetpotato from Papua New Guinea were studied using glucometry and electrochemistry/spectroscopy respectively. The samples were made up of six cultivars (3-mun, Carot kaukau, Wahgi besta, Nillgai, Baiyer kaukau, and 1-mun) planted in three provinces by three farmers in three different locations. The potassium content of the non-digested samples ranged from 4-17 mg/g dry solids, while the starch content was from 47-80 g per 100g dry solids and essentially independent of cultivars, farmers and locations. In-vitro starch digestibility (2-75 g digested starch per 100g dry starch) significantly (p<0.05) varied with time in a non-linear manner, and the starch digestograms exhibited biphasic behaviours irrespective of the sample. We propose that the biphasic behaviour resulted from changes in the digestion kinetics possibly due to barriers to enzyme diffusion by non-starch components. Digestion of potassium was independent of time in in-vitro gastric and pancreatic regions, but pancreatic digestion was significantly (p<0.05) higher than gastric digestion. Results are discussed in the light of the importance of resistant starch and bioavailability of (micro)nutrients for increased utilisation of sweetpotato.

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Puddling: Effect on Soil Physical Properties and Crops

Encyclopedia of Agrophysics, 2011

Long-term flow rates and biomat zone hydrology in soil columns receiving septic tank effluent

Water Research, 2006

Soil absorption systems (SAS) are used commonly to treat and disperse septic tank effluent (STE).... more Soil absorption systems (SAS) are used commonly to treat and disperse septic tank effluent (STE). SAS can hydraulically fail as a result of the low permeable biomat zone that develops on the infiltrative surface. The objectives of this experiment were to compare the hydraulic properties of biomats grown in soils of different textures, to investigate the long-term acceptance rates (LTAR) from prolonged application of STE, and to assess if soils were of major important in determining LTAR. The STE was applied to repacked sand, Oxisol and Vertisol soil columns over a period of 16 months, at equivalent hydraulic loading rates of 50, 35 and 8 L/m 2 /d, respectively. Infiltration rates, soil matric potentials, and biomat hydraulic properties were measured either directly from the soil columns or calculated using established soil physics theory. Biomats 1 to 2 cm thick developed in all soils columns with hydraulic resistances of 27 to 39 d. These biomats reduced a 4 order of magnitude variation in saturated hydraulic conductivity (K s) between the soils to a one order of magnitude variation in LTAR. A relationship between biomat resistance and organic loading rate was observed in all soils. Saturated hydraulic conductivity influenced the rate and extent of biomat development. However, once the biomat was established, the LTAR was governed by the resistance of the biomat and the sub-biomat soil unsaturated flow regime induced by the biomat. Results show that whilst initial soil K s is likely to be important in the establishment of the biomat zone in a trench, LTAR is determined by the biomat resistance and the unsaturated soil hydraulic conductivity, not the K s of a soil. The results call into question the commonly used approach of basing the LTAR, and ultimately trench length in SAS, on the initial K s of soils.

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$Research paper thumbnail of Fitting Performance of Particle-size Distribution Models on Data Derived by Conventional and Laser Diffraction Techniques$

Fitting Performance of Particle-size Distribution Models on Data Derived by Conventional and Laser Diffraction Techniques

Soil Science Society of America Journal, 2009

Mathematical description of most classical particle size distribution (PSD) data is often used fo... more Mathematical description of most classical particle size distribution (PSD) data is often used for estimating soil hydraulic properties. Fast laser diffraction (LD) techniques now provide more detailed PSDs, but deriving a function to characterize the entire range of sizes is a major challenge. The aim of this study was to compare the fi tting performance of seven PSD functions with one to four parameters on sieve-pipette and LD data sets of fi ne-textured soils. The fi ts were evaluated by the adjusted R 2 , MSE, and Akaike's information criterion. The fractal and exponential functions performed poorly while the performance of the Gompertz model increased with clay content for the LD data sets. The Fredlund function provided very good fi ts with sieve-pipette PSDs but not the corresponding LD data sets, probably due to underestimation of the clay fraction in the latter. The two-parameter lognormal function showed better overall performance and provided very good fi ts with both sieve-pipette and LD data sets.

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Soil puddling for rice production under glasshouse conditions—its quantification and effect on soil physical properties

Australian Journal of Soil Research, 2005

The effect of soil puddling on soil physical properties of 3 different textured soils (clay, loam... more The effect of soil puddling on soil physical properties of 3 different textured soils (clay, loam, and silty loam) and growth of rice (Oryza sativa) on these soils was investigated under glasshouse conditions. Puddling intensity was expressed as the ratio of soil volume subjected to the puddling implement and the total soil volume in the puddled layer, thus integrating the effects of speed and time of the puddling operation. This parameter was well related to soil dispersion, bulk density, and saturated hydraulic conductivity. However, following prolonged periods of submerged conditions during rice growth, saturated hydraulic conductivity decreased with a decrease in soil dispersion, in contrast to an expected reduction in saturated hydraulic conductivity with increased dispersion. There was indication that continuous waterlogging reduced the effect of soil puddling, in particular on heavy-textured soils.

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Sensitivity of drainage to rainfall, vegetation and soil characteristics

Computers and Electronics in Agriculture, 2009

Rainfall, vegetation characteristics and soil hydraulic properties influence deep drainage patter... more Rainfall, vegetation characteristics and soil hydraulic properties influence deep drainage patterns in agricultural landscapes, but more information is required on the variability of their interactions with site conditions. Therefore, the objective of the study was to investigate the impact of the interactions of soil permeability, vegetation rooting depth and growth duration on drainage in 3 sites in northern New South

Soil fertility in sweetpotato-based cropping systems in the highlands of Papua New Guinea

The Australian Centre for International Agricultural Research (ACIAR) was established in June 198... more The Australian Centre for International Agricultural Research (ACIAR) was established in June 1982 by an Act of the Australian Parliament. Its mandate is to help identify agricultural problems in developing countries and to commission collaborative research between Australian and developing country researchers in fields where Australia has a special research competence. Where trade names are used this constitutes neither endorsement of nor discrimination against any product by the Centre.

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Variation in plant available water and hydraulic conductivity along transects of different textured soils

The physical properties of hardsetting soils in Australia and the Philippines: towards a definition of hardsetting

Effect of wetting and drying on structural regeneration of puddled soil

The effect of repeated wetting and drying and the degrees of drying on structure regeneration of ... more The effect of repeated wetting and drying and the degrees of drying on structure regeneration of puddled soil were studied on two soils, e.g., a grey clay and a sandy loam soil. Degrees of drying were arranged by sun drying at different periods, e.g., 2-4 days, 5-8 days and 9-12 days drying, which were corresponding to pF 2.12.5, 3.1-3.8 and 4.6-6.0 respectively. Five wetting/drying cycles were conducted during this experiment. Measurements on the effect of different degrees of puddling showed that the two soils responded quite similar towards partially drying. An increased in the degree of drying resulted in faster improvement of soil structure.. Drying the puddled soil to its air dry water content is very effective in the process of structural regeneration. But this study also showed that the regeneration of puddled soil is possible by partial drying.

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Management of clay soils for rainfed lowland rice-based cropping systems. Proceedings of ACIAR international workshop held at the Bureau of Soil and Water Management, Quezon City, Manila 20-24 November 1995

Management of clay soils for rainfed lowland rice-based cropping systems

Soil and Tillage Research, 2000

Root zone temperature alters storage root formation and growth of sweetpotato

Journal of Agronomy and Crop Science

Compaction properties of vertisols and their potential effect on sunflower

Growth of vineyard roots into segmentally ameliorated acidic subsoils

Plant-Soil Interactions at Low pH, 1991

... Australian Industrial Publishers, Adelaide, Australia. Freeman BM and Smart RE 1976 A root ob... more

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