Two trials using Lupinus angustifolius cv. Uniharvest were conducted in the summer of 1978-1979 at Lincoln College, Canterbury. From the first trial, designed to measure dry matter accumulation and changing nutritive value of lupins with time, a maximum dry matter yield of just under 990 kg ha⁻¹ was obtained 150 days after sowing. Peak digestibility was 65.0 per cent and was recorded at 125 days after sowing. Protein concentration was highest in the young plant (28.75 per cent at 45 days after sowing) and declined after this, but highest total nitrogen yield coincided with peak dry matter accumulation. In the second trial, lupins at 60 and 100 plants m⁻² were grazed with weaned lambs at each of four successive stages of the plants' growth - pre-flower, primary flower, secondary flower and green pod (post-flower). Highest dry matter accumulation,at just under 1 000 g m⁻², occurred at the green pod stage, and peak protein concentration of 23.7 per cent at the pre-flower stage (lower density). Digestibility was highest at the pre-flower stage (higher density) and the metabolizable energy concentration was also highest in the pre-flower high density plots. Regrowth of lupins following grazing occurred in plots which had been grazed at the pre- and primary flower stage. Maximum total dry matter accumulation from the first grazing combined with the regrowth was 1 350 g m⁻². Digestibility, protein and metabolizable energy concentration of the regrowth was at acceptable levels for animal growth. From the results obtained, and those of other workers, both in New Zealand and overseas, it is suggested that lupins may have considerable potential as a high quality summer forage crop for grazing of young lambs.

The insect fauna of two Lupinus angustifolius cultivars (Fest and Uniharvest) was surveyed between October, 1978 and March, 1979. The main sampling methods were sweepnetting, use of the D-Vac, and pod removal. Glasshouse experiments were carried out with species showing pest potential (based on the survey). These species were Acyrthosiphon pisum (Harris), Nysius huttoni White, and Sidnia kinbergi (Stalenberg). While A. pisum and S. kinbergi had their pest potential confirmed, N. huttoni did not. Although the aphids Acyrthosiphon kondoi Shinji, Macrosiphum euphorbiae (Thompson) and Myzus persicae (Sulzer) were not studied in the laboratory, field data indicated their pest potential. Insects to show lesser pest potential were Calocoris norvegicus (Gmelin), Hylemyia deceptiva Malloch, and Hylemyia platura (Meigen). Important potential predators or parasites were Austromicromus tasmaniae (Walker), Coccinella undecimpunctata L., Tropiconabis capsiformis (Germar), some Araneae species and single unidentified species of Braconidae and Eulophidae. The cultivar Uniharvest was the preferred host presumably because it does not possess the toxic alkaloids of Fest. However, crop loss through insect damage appeared unimportant compared to the 10% loss of Uniharvest caused by the aphid-borne bean yellow mosaic virus.

The incorporation of cereal straw/stubble often immobilises nitrogen (N). This can help conserve N in soil in organic forms, thus reducing loss through leaching over dormant winter periods. However, N-depressions that arise during decomposition can reduce crop yield. The inclusion of a legume green manure can supply fixed-N, thus alleviating the low N availability to crops. In this study, the effect of lupin (Lupinus angustifolius L.) green manure incorporation on barley (Hordeum vulgare L.) straw/stubble decomposition, and N availability was investigated. A field experiment was used to determine the effects of the green manure on decomposition. Decomposition of straw/stubble was monitored using the litterbag technique. Following green manure incorporation, soil cores were incubated in a glasshouse to determine mineral-N availability. Though not significant, the inclusion of lupin green manure seemed to increase the decomposition of straw/stubble during the growth period, then slowing it after its incorporation at 110 d. This was described by a logarithmic pattern of loss of - 4.97 g AFDW residue day⁻¹, with 60% remaining after 140 d. Treatments without lupin had a linear decomposition of - 0.12 g AFDW residue day⁻¹, with 49% remaining after 140 d. The loss of cellulose confirmed the differences in decomposition with the inclusion of lupin resulting in 2.79% less cellulose remaining in straw/stubble after 140 d compared to its exclusion. Lupin significantly increased pot oat N uptake and DM yield by 55 % and 46 %, respectively, compared to its exclusion. However, this effect was not observed in field sown wheat yields and the soil mineral-N measurements made. This study showed that the potential of lupin to increase straw/stubble decomposition by improving the retention and availability of N, leading to long-term yield benefits, needed further investigation.

[Truncated abstract] The hydraulic properties of the roots of three crop species important to Western Australia were examined: wheat (Triticum aestivum), narrow-leafed lupin (Lupinus angustifolius) and yellow lupin (L. luteus). Generally, the hydraulic conductivity (Lpr) of root systems differs between species and can change in response to adverse conditions. To determine the significance of root anatomy and aquaporin activity on the pathway of water flow through roots, water flow was measured across cell membranes, individual roots and whole root systems. The combination of measurements identified that wheat and lupin roots have contrasting hydraulic properties. Wheat roots absorb water preferentially in the apical region, whereas lupin roots appear to absorb water more evenly along the entire root length. Lupin roots have a greater axial hydraulic conductance than wheat, due to more abundant xylem vessels and axial conductance increases with root length, in conjunction with xylem vessel development. However, water flow through the radial pathway is the limiting factor in whole root hydraulic conductance, in all species. Modelling and the inhibition of aquaporin activity with mercuric chloride demonstrated that radial water flow in wheat roots occurs by a combination of the cell-to-cell and apoplastic pathways, but in lupins, water flow appears to be predominantly apoplastic. Despite the presence of aquaporins in root cell membranes of all species, their role in regulating bulk water flow across roots is not clear in lupins, because of the significance of the apoplastic pathway ... After draining the chambers, the root systems of yellow lupin resumed growth, but there was no subsequent recovery in narrow-leafed lupin root systems. The growth and survival strategies of wheat and lupin root systems are disparate. Wheat root systems are comprised of numerous fine, highly branched, individual roots that extract water near the root tips and have the ability to regulate flow. These attributes may be advantageous in non-uniform or variable environments. Moreover, the ability of wheat roots to regulate flow may not only support survival during waterlogging, but also enhance recovery. In comparison, lupin root systems are designed like conduits, for the rapid uptake and transport of water when conditions are favourable. However, their thick taproots and lack of regulation of water transport or anatomical changes make them unsuitable for very wet soils.

To date, there has been little research into the role of microbial community structure in the functioning of the soil ecosystem and on the links between microbial biomass size, microbial activity and key soil processes that drive nutrient availability. The maintenance of structural and functional diversity of the soil microbial community is essential to ensure the sustainability of agricultural production systems. Soils of the same type with similar fertility that had been under long-term organic and conventional crop management in Canterbury, New Zealand, were selected to investigate relationships between microbial community composition, function and potential environmental impacts. The effects of different fertilisation strategies on soil biology and nitrogen (N) dynamics were investigated under field (farm site comparison), semi-controlled (lysimeter study) and controlled (incubation experiments) conditions by determining soil microbial biomass carbon (C) and N, enzyme activities (dehydrogenase, arginine deaminase, fluorescein diacetate hydrolysis), microbial community structure (denaturing gradient gel electrophoresis following PCR amplification of 16S and 18S rDNA fragments using selected primer sets) and N dynamics (mineralisation and leaching). The farm site comparison revealed distinct differences between the soils in microbial community structure, microbial biomass C (conventional>organic) and arginine deaminase activity (organic>conventional). In the lysimeter study, the soils were subjected to the same crop rotation (barley (Hordeum vulgare L.), maize (Zea mais L.), rape (Brassica napus L. ssp. oleifera (Moench)) plus a lupin green manure (Lupinus angustifolius L.) and two fertiliser regimes (following common organic and conventional practice). Soil biological properties, microbial community structure and mineral N leaching losses were determined over 2½ years. Differences in mineral leaching losses were not significant between treatments (total organic management: 24.2 kg N ha⁻¹; conventional management: 28.6 kg N ha⁻¹). Crop rotation and plant type had a larger influence on the microbial biomass, activity and community structure than fertilisation. Initial differences between soils decreased over time for most biological soil properties, while they persisted for the enzyme activities (e.g. dehydrogenase activity: 4.0 and 2.9 µg g⁻¹ h⁻¹ for organic and conventional management history, respectively). A lack of consistent positive links between enzyme activities and microbial biomass size indicated that similarly sized and structured microbial communities can express varying rates of activity. In two successive incubation experiments, the soils were amended with different rates of a lupin green manure (4 or 8t dry matter ha⁻¹), and different forms of N at 100 kg ha⁻¹ (urea and lupin) and incubated for 3 months. Samples were taken periodically, and in addition to soil biological properties and community structure, gross N mineralisation was determined. The form of N had a strong effect on microbial soil properties. Organic amendment resulted in a 2 to 5-fold increase in microbial biomass and enzyme activities, while microbial community structure was influenced by the addition or lack of C or N substrate. Correlation analyses suggested treatment-related differences in nutrient availability, microbial structural diversity (species richness or evenness) and physiological properties of the microbial community. The findings of this thesis showed that using green manures and crop rotations improved soil biology in both production systems, that no relationships existed between microbial structure, enzyme activities and N mineralisation, and that enzyme activities and microbial community structure are more closely associated with inherent soil and environmental factors, which makes them less useful as early indicators of changes in soil quality.