Ian Valentine

Influence of pastoral fallow on plant root growth and soil physical and chemical characteristics in a hill pasture

Pastoral fallowing over a growing season (October–May) has a profound effect on standing biomass and sward structure, and should have an impact on below ground plant growth and soil biological activities. Two field studies were conducted to compare the effects of pastoral fallow with rotational grazing on root growth and soil physical and chemical properties. Root growth and distribution was altered by pastoral fallowing and there was significantly (P < 0.01) less root biomass at 0–50 mm depth of soil in the fallowed sward than the grazed sward. Compared with the grazed treatment, pastoral fallow increased soil air permeability at 500 mm tension by 38%, saturated hydraulic conductivity by 26%, unsaturated hydraulic conductivity at 20 mm tension by 67% and soil moisture by 10–15%, and reduced soil bulk density by 11%. Fallowing had little effect on soil nutrients both at the end of fallowing, except for small reductions in K and Mineral N levels at 0–75 mm soil depth, and two to three years after fallowing.

The influence of topography and pasture management on soil characteristics and herbage accumulation in hill pasture in the North Island of New Zealand

The aim of this study was to examine long-term effects of fertiliser and livestock management and micro-topographical variation on soil physical and chemical characteristics and herbage accumulation on a hill site in the southern North Island of New Zealand.Paddocks subjected to high fertility-high stocking rate (HH) and low fertility-low stocking rate (LL) treatments dating back to 1975 were used. Soil samples were taken from three slope categories (0–12 ° low slope, LS; 13–25 ° medium slope, MS; >25° high slope, HS) from HH and LL and a range of soil chemical and physical features were assessed. Herbage accumulation (green matter and dead matter) was measured over 12 months on each microsite.Greater differences in soil and herbage features, such as unsaturated hydraulic conductivity (Kunsat), bulk density (BD), water holding capacity (VSM), soil compressibility (SC), total soil nitrogen (Total-N), Olsen-P and green dry matter accumulation (GDMA), were measured across slope categories than between management treatments, possibly because slope effects on soils would have operated over longer periods of time than the fertiliser-stocking rate contrasts. Increasing slope decreased GDMA on the site, as well as Total-N, Olsen-P, VSM and SC, but increased Kunsat, BD and soil rebound after compression (SR). Slope, VSM, Kunsat, SC, BD and Total-N were the soil variables with largest influence on differentiation between microsites. Olsen-P and SR were less important. Green dry matter accumulation was strongly influenced by slope, soil VSM and Kunsat, and to a lesser extent by soil Total-N and Olsen-P.

Influence of the timing and duration of pastoral fallowing and nitrogen fertiliser on pasture and white clover (Trifolium repens) growth in hill country

Abstract In a hill pasture in New Zealand, pastoral fallows starting from December, January, and February and terminating in June significantly (P < 0.01) reduced the tiller density of grasses, the dominant species in the sward. At the conclusion of these fallows, the plant population (grass + legume + weed) density was only 29–49% of the grazed control. Fallows from December and January to June significantly (P < 0.01 and P < 0.05, respectively) increased the internode length of white clover. Only the December fallow significantly (P < 0.05) increased the viable seed population of grasses, whereas for other treatments and other species in the December fallow there was no significant difference between the fallowed and grazed swards. The addition of fertiliser nitrogen significantly (P < 0.05) enhanced the decline in tiller density for the March to June fallow from the time of application. It improved the specific stolon weight of white clover and reduced the viable seed population of weeds and rushes (P ...

Enhancing the utility of science: exploring the linkages between a science provider and their end-users in New Zealand

Increasingly, publicly funded research is being required to demonstrate its contribution to the public good. In response to this trend, a science provider of soil quality research in New Zealand initiated a research project that set out to identify and characterise its end-users in order to improve the utility of their research. The researchers recognised the complex nature of this problem and adopted an action research approach based on soft systems methodology (SSM). The research process entailed 4 action research cycles, allowing greater levels of problem redefinition and participant learning. The quality of linkages between the science provider and their end-users was found to be crucial for improving the utility of that science, and is determined by: (i) the nature of the personal relationships between them, (ii) how the information meets the needs of the end-users, (iii) the end-users’ perceptions of the science provider, and (iv) the culture and structure of the end-user organisations.

Sustainability of grazing systems: Feed base, critical grazing pressure and variability

This paper proposes a method for estimating the feed base, grazing pressure and variability as an indicator of risk, in grazing lands. Together, they may be considered as surrogate measures of biophysical sustainability. The paper applies them to four transects, each from unfertilised rangeland to relatively intensive mixed farming in temperate Australia. Across the transects, the feed base, stocking rates and grazing pressure in 1987–97 increased with increasing median annual rainfall, and grazing pressure decreased with increasing inter-year variability in the feed base. Average year-round grazing pressures generally ranged from 0.2 to 0.3–0.5. Periods of critical grazing pressure, defined as times when the calculated feed base fell below some critical value, say 0.7 tha−1, decreased markedly with increasing rainfall and decreasing variability in the feed base. Long periods of critical grazing pressure in areas receiving less than 400mm rainfall suggests grazing practices may be unsustainable. Stocking rate and annual average grazing pressure (with or without account for feral animals) did not appear to be, in themselves, good indicators of sustainability. Rather, the sustainability of different areas/systems and the impacts on sustainability of changes in management, e.g. stocking rates, may be assessed better through calculating year-to-year variability of the feed base, and periods of critical grazing pressure.

Plant functional groups in a heterogeneous environment

Abstract Species membership of plant functional groups and the relationship to soil variables were studied in two paddocks with long‐term differentiated management in New Zealand hill country. The microrelief of the paddocks contained three slope classes (low, medium, and high) with contrasting soil variables. Soil variables (unsaturated hydraulic conductivity, bulk density, volumetric soil moisture, total soil porosity, field volumetric soil moisture, soil compression, soil rebound, and air permeability), botanical composition and herbage mass accumulation were determined. Analysis of variance, cluster analysis, simple correlation analysis and canonical variate analysis were performed on the data. Seven functional plant groups were determined. High fertility grasses and Lolium perenne were strongly affected by changes in the level of soil variables. Low fertility species appeared to be affected indirectly by soil variables, as they were poor competitors when availability of soil resources was high. Some species (e.g., Agrostis capillaris) were indifferent to changes in the levels of available resources due to soil characteristics. Species and functional groups colonised the evaluated sites according to the soil resources. Species and functional groups were shown to have the capability to respond positively to soil resources, adjusting their growth according to the varying circumstances. The relationship between plant functional groups and field condition, a grazing management concept that measures the deviation from some ideal ecological state, was also examined. Results suggested that field condition and plant functional groups are complementary concepts in grassland dynamic analyses.

SSM-Guided Research to Improve the Linkages between a Science Provider and their End-Users

People make sense of the world differently, some are guided by systems thinking and some are not. This has implications for systemic practitioners and the way they interact with others who do not see the world as they do. This paper describes the evolution of a process of inquiry to date that has been explicitly influenced by systemic researchers. The authors attempt to make sense of their experiences and to highlight some important aspects of the inquiry process to date. Highlighted in particular, are the stages and manner in which the client was involved in the process, and how the way information from the rich-description was conveyed to the client influencing the way in which the problem situation was viewed and action defined by the client.