Massey Documents by Type
Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294
Browse
11 results
Search Results
Item Aluminium interaction with organic matter and fluoride during soil development in oxidised mine waste : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Soil Science, Massey University(Massey University, 1994) Gurung, ShivarajSignificant differences in plant growth response between unmodified waste rock (UWR) and modified (treated with lime and phosphate fertilizers) waste rock (MWR) with topsoil treatments during the first two years of a field trial conducted by Gregg & Stewart (1986; 1987) indicated that Al toxicity was affecting root growth in the UWR. By the end of three years of field trial there was no significant difference in dry matter yield between the MWR and UWR with topsoil treatments indicating possible amelioration of Al toxicity (Gregg et al., 1990). The objective of this study was to measure different forms of Al and F in the soil and waste rock at the end of the third year of field trial and to determine the mechanism of amelioration of Al toxicity in these soils. Results of this study revealed that there was a significant 2-fold increase in organic-Al (Al-OM) at the UWR interface (B) compared with the waste rock at depth (C) by the end of three year period of soil development. Organic matter decomposition in the topsoil during three years and movement of the soluble organic ligands to UWR interface (B) resulted in conversion of phytotoxic soil solution Al into non-toxic Al-OM forms by complexation with organic ligands in leachates accumulated in the UWR interface. Total soluble F was consistently high in the UWR profile with a mean value ranging from 1.0 to 1.9 µ,g g·1 . Liming has reduced the F level to 0.3-0.4 µ,g g·1 in the MWR interface (B) and 0.4-0.5 µ,g g·1 in the topsoil (A). The waste rock at depth (C) had mean F values in the range 1.2-1.9 µ,g g·1 . High levels of F in the waste rocks could have also ameliorated Al toxicity in the UWR by formation of non-phytotoxic soluble AlF complexes. This was considered to be another possible reason for no significant differences in the pasture yields between UWR and MWR plots at the end of the third year of trial. The mean soil pH(H20 ) for the UWR was 5.1 and liming has raised it by about 1 unit in the MWR. The corresponding pH(0.01 M CaCl2) values were 0.4-0.8 units less than the pH in water. The 0.02 M CaC12-extractable solution Al (Al-Ca) and 1 M KCl- extractable exchangeable+ solution Al (Al-K) have remained high in UWR soil solution irrespective of different depths of topsoil treatments. The Al-Ca and Al-K ranged from 16.7 to 20.5 µ,g g·1 and 261 to 339 µ,g g·1 respectively in the UWR interface (B). The Al-Ca and Al-Kin waste rock at depth (C) remained at 16.8-22.9 µ,g g·1 and 238-369 µ,g g·1 respectively. Modifications have lowered both Al-Ca and Al-K to 0.8-2.7 µ,g g·1 and 35-66 µ,g g·1 respectively in the MWR interface (B). Topsoil Al-Ca and Al-K were not significantly different between UWR and MWR and the values for these two forms of Al ranged from 0.6 to 6.0 µ,g g·1 and 32-87 µ,g g·1 respectively at the end of the field trial. Normal plant growth response in the UWR in spite of high levels of Al-Ca and Al-K indicated that 0.02 M CaC12 and 1 M KCl extractants are not good indicators of phytotoxicity as reported in literature because these extractants may be extracting a substantial proportion of non-phytotoxic species of Al.Item Influences of climate and fertiliser application history on various measures of soil fertility and productivity in Wairarapa hill country : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Soil Science at Massey University, New Zealand(Massey University, 1994) Moir, James LaingDuring the agricultural downturn of the mid 1980's, it became uneconomic for many Wairarapa farmers to apply fertiliser. Those farmers who could afford to apply maintenance fertiliser, often chose to apply diammonium phosphate (DAP). The increasing popularity and apparent effectiveness of fertilisers such as DAP, which has a nitrogen component, prompted further questions of whether traditional P and S fertiliser application (as single superphosphate), applied to stimulate pasture legume growth and biological nitrogen fixation, was the most cost effective fertiliser strategy. A review of literature revealed that soil fertility and pasture production data for different rainfall regimes in the Wairarapa was scarce. No published data was available on how effective single superphosphate (SSP) applications to Wairarapa hill country farms had been in increasing annual N fixation rates and plant available soil N, and hence increasing pasture production. It was concluded that it was necessary to conduct a series of pasture field trials on sites varying in soil type, fertiliser history and climate (annual rainfall) in order to provide data applicable to the Wairarapa region. Sites falling within three rainfall regimes were selected, those being Mauriceville (high rainfall), Gladstone (summer dry) and Whareama (low rainfall) sites. Using total soil phosphorus, sulphur and nitrogen analyses, a total of 14 sites were selected for study, with sites ranging in fertility status within each climate zone. The objective has been to characterise the soil types, soil nutrient status, climate and current pasture production of Wairarapa hill country farms, with a view to completing further studies examining in more detail the complex interactions of soil, climate and pasture. Soil chemical analyses revealed a wide range of soil fertility status across all sites. Soil total phosphorus (P) contents ranged from 430 µgP/g soil (site 4) to 1470 µgP/g (site 1), while total soil sulphur (S) showed less variation, ranging from 345 µgS/g (site 11) to 860 µgS/g (site 9). Soil total nitrogen (N) contents followed a similar pattern to that seen for total S, and ranged from 4280 µgN/g (site 11) to 7950 µgN/g (site 9). Fertiliser history had a large influence on the accumulation of P, S and N in these hill country soils, where higher rates of accumulation were associated with greater levels of fertiliser input. However, P accumulated at a far greater rate than S and Nin these soils, which is possibly the result of high S and N leaching losses. Measurements of plant-available nutrient levels followed a similar trend to that seen for soil total elemental analyses, where higher levels of nutrient were correlated with higher fertiliser inputs. Estimates of the efficiency of past fertiliser applications were made for these sites, using the results of various soil analyses. Traditional P and S fertiliser applications and pasture management on Wairarapa hill country appear to have been particularly inefficient in causing soil N to accumulate. The calculations used to derive these estimates have limitations, but do indicate that either product N and leaching losses are high or N fixation rates are low (or both) in these soils. July 1993 to March 1994 was an average growing season, and total herbage yields harvested from August 1993 to March 1994 ranged from 4 tDM/ha (site 4) to 15.5 tDM/ha (site 1). Soil fertility status (and hence historical SSP applications) was the main factor influencing total herbage yield, where high yields were recorded at high fertility sites, and the reverse for low fertility sites. Climate (soil moisture levels) also influenced total yield but to a lesser extent than soil fertility status. Pasture growth at Gladstone and Whareama sites stopped when soil volumetric water content in the top 7.5 cm fell below 0.2. At the wetter Mauriceville sites, soil moisture was not limiting until mid-February 1994. Legume growth was particularly sensitive to soil moisture stress. By converting pasture production to stock units, gross margin analyses were performed. The most profitable options in all three rainfall regimes were sites which had received frequent fertiliser applications. This suggests that historical fertiliser applications are economically effective, which is an important factor in sustainable agricultural enterprises. Herbage N and P uptake results supported this finding, and showed that pasture N uptake varied widely between high and low fertility sites. Pasture N uptake ranged from 70 kgN/ha at low fertility site 4, to 250 kgN/ha at high fertility site 1 for the period of early August 1993 to early January 1994. This implies that historical superphosphate applications have been effective in providing large increases in annual amounts of plant-available soil N at high fertility sites when compared to unfertilised sites, despite the fact that soil N accumulation was less than expected. Acetylene reduction activity (ARA) measured at each harvest showed that annual N fixation levels are limited by extended summer dry periods which stop legume growth. The wetter Mauriceville sites fixed more N on an annual basis than Gladstone and Whareama sites. ARA was linearly related to yield. Variations in the data indicated that species and other short-term soil condition changes have a large effect on the relationship between ARA and N fixation rates. Although soil N accumulation is slow in these pasture systems, annual pasture N uptake is dramatically increased where fertiliser inputs have been high. The results indicate that rapid cycling of soil/plant N is occurring, and that annual leaching and product losses of N may nearly equal N fixation rates. This was exemplified in a simple budget of the nitrogen cycle, taking account of N losses and gains in a low fertility and high fertility system. There was insufficient information to conclude why soil N is not accumulating in these grazing systems. Further research is required to fully explain this N cycle, including the relative quantities of N inputs and losses from the system.Item The influence of cultural practices on soil organic matter, soil biomass size and nitrogen leaching : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science (Agricultural Environmental Science) at Massey University, New Zealand(Massey University, 1994) Mapfumo, PhillimonThe effects of bare fallow, cultivation and nitrogen application on soil organic matter, soil biomass and nitrogen leaching were compared against the backgrounds of permanent grass pasture and grass/clover pasture. Cultivated plots were dug annually to a depth of 15cm. All plots received an annual dressing of 300kg ha·1 of Potassic Super. The Nitrogen treatment was applied as two equal applications of 100kg ha·1 Calcium Ammonium Nitrate in November and December each year. The results indicated that both bare fallowing and cultivation reduced soil organic matter and soil microbial biomass. The use of N-fertilizer did not promote either the soil organic matter or soil microbial biomass; this is contrary to the general finding. Legume nitrogen was found to leach as readily as the applied nitrogen and hence posed an environmental threat to groundwater quality. In all cultural practices the largest concentration of nitrate nitrogen (NO3-N) was observed at the 50 - 100m depth, below the root zone. Vertical movement of groundwater was estimated at lm year·1 This confirmed the concern of possible groundwater pollution by nitrate nitrogen from agricultural activities.Item Nutrient accumulation in soils under long-term farm dairy effluent application : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Applied Science in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2005) Cox, JulietLand-based application of farm dairy effluent (FDE) has been encouraged by regional councils since the introduction of the resource management act (RMA) in 1991. The problems associated with FDE irrigation are high levels of nitrate in ground and surface waters which can lead to human health issues where the groundwater is used as drinking-water and environmental degradation of streams, rivers and lakes. Regional councils impose nitrogen loading limits to reduce the likelihood of environmental problems from nitrate leaching. Long-term data investigating FDE application and the associated soil changes over time is currently unavailable and the nutrient budgeting tool OVERSEER® Nutrient Budgets 2 is validated against only short-term trials. Therefore, assumptions made in the model for long-term FDE application areas may not be correct. The project investigated the soil chemical characteristics of six long-term (>6 years) farm dairy effluent paddocks and matched non-effluent paddocks in the Waikato and Bay of Plenty. Fieldwork involved the removal of five core samples from each paddock, with each core yielding six sub-samples of 75 mm depth. Soil analyses included bulk density calculations, cation exchange capacity, total carbon, nitrogen and phosphorus determination and Olsen P. It was found that two sites had the same total cation exchange capacity in the effluent and non-effluent paddocks, but the proportions of the individual cations were different. A significant (α = 0.05) difference in the exchangeable potassium concentration existed between the pairs of paddocks with much greater potassium found in the areas irrigated with FDE. No discernable difference in the concentrations of carbon and nitrogen was found between the topsoil of the effluent and non-effluent paddocks. This was due to the highly variable nature of the effluent and the soils themselves, and the large pool of nutrients in the soil, requiring a large change before a noticeable difference occurred. The total nitrogen and phosphorus levels found in the soil profiles (0-450 mm) of the effluent and non-effluent paddocks were very similar, and reflects the large additions of fertilisers to non-effluent paddocks. The OVERSEER® Nutrient Budgets model was used to produce nutrient budgets for farms from the Waikato and Bay of Plenty and predictions of accumulation of nutrients over time. Comparisons made between the OVERSEER® results and soil chemical analyses revealed that with the exception of potassium, it was not possible to accurately predict the nutrient concentration in the soil by extrapolation of OVERSEER® data. This was due to changes in management practices over time and the inherent variability of soils. If the model is to be used as a regulatory tool, accurate fertiliser records must be kept, along with frequent pasture and soil analysis. It is also advisable that a soil map of the farm area is completed in order to most accurately use the model.Item Relationship between soil fertility and the components of and seasonality of forage supply of a hill pasture(Massey University, 1994) Pino Machado, Amabelia S. delSeven hill country sites, covering a range of soil fertility were studied with the objective of examining the relationship between soil fertility indices and the components of and seasonality of forage supply of a hill pasture under continuous grazing. The seven sites varied from an undeveloped, unfertilized hill pasture, containing only low fertility adapted grasses and weeds to a highly productive sward dominated by high fertility responsive grasses and white clover. The differences between sites were the consequence of different fertilizer application, position on the landscape and accumulation of nutrients from dung and urine. The total C content of the soils varied from 4.7 to 7.2%, N content varied from 0.43 to 0.70% and P content from 517 to 1361 mg L-1.Soils were sampled biweekly and analyzed for mineral N and Olsen and Resin P for 12 months starting in January 1993. In each season microbial C, N and P were also measured. Pasture growth and components at each site were assessed under biweekly and 4-weekly cutting regimes throughout the 12 months of the experiment. Nitrogen and P concentration of mixed pasture samples from each cut were also determined. There was a wide range in the values of the three soil fertility indices measured (mineral N, Olsen P and Resin P). Ammonium was the dominant form of soil mineral N at all but the highest overall soil fertility site. Differences in mineral N between sites were mainly due to NO-3 content. The seasonal pattern was similar for all sites with the lowest soil mineral N content in winter and the highest in summer. In contrast both soil P indices had smaller variation throughout the year and no clear seasonal pattern. Olsen P values at the seven sites ranged from 7.7 to 46.3 and Resin P values from 12.2 to 76.7. Microbial C and N content of soil showed little seasonal variation or differences between sites. In sharp contrast, Microbial P was higher in spring and summer than in autumn and winter and this difference decreased as the fertility of the seven sites increased. The Microbial C:P ratio decreased as fertility increased. Annual pasture production varied more than 5-fold across the 7 sites, ranging from 3300 to 17000 kg DM/ha/year. There was little effect of cutting frequency on pasture production. Grasses adapted to low fertility environments were the dominant botanical fraction of pasture at all sites with the exception of the highest production site. High fertility responsive grass production followed the same trend as total pasture production and weeds the opposite trend. The seasonal pattern of pasture production was similar at all sites with spring and summer production accounting for more than 70% of annual production. Seasonality of pasture growth was not affected by soil fertility or cutting frequency. Nitrogen and P concentration of pasture followed the same trends of pasture production being the highest in the high production sites and extremely deficient in the low production sites. Differences in P uptake by pasture were far greater (nearly 10-fold) than differences in pasture production. There were strong relationships between the three soil fertility indices studied and pasture growth. Monthly and seasonal mineral soil N values had a strong linear relationship with seasonal and annual pasture production indicating that N was limiting pasture growth over the range of soils studied. Spring and summer estimates of mineral N were the most reliable predictors of annual pasture production. Monthly and seasonal values of soil P fertility indices (Olsen and Resin P) were strongly related to pasture production although pasture growth appeared to be reaching a plateau at high P levels, specially in spring and summer. Due to the small variability of these indices throughout the year, relationships between Olsen P and Resin P and total pasture production were independent of sampling time, with the exception of the sampling immediately following P fertiliser application. Estimated P levels for 95% of maximum growth were extremely high (103 and 187 μg/cc for Olsen P and Resin P, respectively). These indices are much greater than the commonly used critical level for Olsen P in these soils (20 μg/g). However, the shape of the response curve in this study may be affected by the combined effect of available P and N at the high fertility sites. Indices of P fertility were also related to pasture composition, with a strong positive linear relationship with high fertility responsive grass production, a quadratic relationship with white clover production and a negative relationship with weeds production and content. This study suggests that in hill country pastures Olsen P and Resin P values may be satisfactory indicators of pasture productivity for animal production models. However, pasture production will continue to increase to much higher P levels than are normally associated with maximum production in conventional P fertiliser trials. This is because of the linkage of N and P in animal excreta resulting in a high nitrogen status in those areas of hill country that also have high P.Item Effect of organic crop rotation on soil fertility : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Soil Science, Massey University(Massey University, 1995) Sutassanamalee, AngsanaStudies of soil nutrient fertility status of the organic and conventional plots at the Flock House cropping and organic units, Bulls, were undertaken to investigate the effects of organic crop rotation system on soil chemical fertility. Soil samples (0-75 mm, 75-150 mm, 150-300 mm depths) were collected from two organic plots lying adjacent to conventional plots of identical soil type (Manawatu silt loam) in Autumn and Spring. The crop rotation plots were established in 1988. Soil samples were analysed for total C, total N, mineralizable N, extractable P (Olsen), exchangeable K, CEC and pH. Earthworm surface casts collected from the surface of these plots were also analysed for exchangeable K and CEC. Results of this study showed that after seven years of conversion to organic management, there were significant quantitative increases in the soil nutrient levels at topsoil depth 0-75 mm. Organic plot number 3 (OP3), now under clover based pasture showed higher percent of organic C and N than the organic plot under continuous cultivation (OP5) and conventional plot (CP8). Mineralizable N was significantly higher in the soil of OP3 and the mean topsoil (0-75 mm) value increased from 104 to 139 μg g-1 (67%) from Autumn to Spring collected soils. Crop rotation under continuous cultivation resulted in decrease of mineralizable N from 90 to 30 μg g-1 (150%) from Spring to Autumn collected soils at depth 0-75 mm. Extractable soil P (Olsen) remained significantly high in CP8 in both Autumn and Spring seasons. Soil Ca and Mg were significantly higher in the organic plots during Autumn but there was no significant difference observed in Spring collected soils. Exchangeable K levels were similar under both organic and conventional management system and generally showed higher amounts at topsoil (0-75 mm) as a result of mixing with earthworm surface casts which contained appreciably high amounts of K, Ca and Mg. Soil CEC was generally higher in organic plots. Surface casting by earthworm was significantly higher (> 1000 casts m-2) in OP3 as compared to 380 casts m-2 and 300 casts m-2 in OP5 and CP8 respectively. This coincided with greater a cation nutrient status observed in the Spring collected soil samples. Organic management under different crop rotation system resulted in significantly variable levels of soil nutrient fertility. Seven years of crop rotation under the organic system was sufficient to maintain sustainable levels of soil nutrient fertility.Item Farm management and soil quality : an investigation into the effects of conventional and organic crop rotation systems on soil quality indicators : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Agricultural Science in Soil Science at Massey University(Massey University, 1995) Steensel, Frank vanThe physical and biological properties of soil from the pasture phase of organic and conventional crop rotation systems were compared. At the same time, a similar comparison was made of soil from the crop phase versus soil of the pasture phase of organic plots. A search was started for a new biological indicator of soil quality. The potential use of the relative abundance of fluorescent pseudomonad bacteria in rhizosphere soil and on the rhizoplane of plants in conventional and organic plots was explored. Soil respiration was also evaluated as an indicator of soil quality. Several soil amendments including earthworm casts, rhizosphere soil, compost material and biodynamic "preparation 500" were examined for their effect. The research has concluded that; 1. The pasture phase of organic crop rotation had superior soil quality to the similar pasture phase of the conventional plot. 2. Though recently cultivated, the pasture phase of the organic rotation system was able to restore appropriate levels of soil quality. 3. The relative abundance of fluorescent soil pseudomonad bacteria was greater in soil from the organic plot. 4.Based on soil respiration activity, none of the organic amendments were able to show a stimulation of soil biological activity in soil from organic or conventional crop rotation plots.Item A review of the nature of beef cattle industry in the Solomon Islands with emphasis on soil fertility factors influencing pasture production on selected farms : a thesis presented in partial fulfilment of the requirements for the Masters degree in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2012) Sefa, Simon IroA general review of primary production in the Solomon Islands indicated that cattle grazing is mainly an activity involving smallholder farmers for cash income and consumption for their extended families. The review and a farm survey indicated that the productive capacity of pasture soils and many agricultural soils in Solomon Islands, continues to decline because poor, near-subsistence, farmers are unable, for economic reasons and lack of training, to provide land management strategies for crops and grazed pastures that maintain or improve soil fertility. This thesis reports on three investigations undertaken to assess the fertility levels of some pasture soils in Solomon Islands. This knowledge is required to develop soil fertility management strategies to assist in sustaining the productivity of grazed pasture and the beef cattle industry in the country. The review indicated that most soils are developed from volcanic materials and a few from corals. Most land considered suitable for agricultural use has not been characterised and recorded. Increasingly, the soils require additional sources of nutrients as they only obtain nutrients from decomposed organic matter and weathering soil minerals. Four farms (ASI, ILA, NAC, and STJT) were selected and surveyed focussing on examining their general background information, identification of pasture species, and evaluating the efficiency of record keeping practices. The pasture grass/legume species identified on the farms are T-grass, Carpet grass, Paragrass, White clover, Puero, Centro and Mimosa. Attempts to maintain soil fertility were based on traditional methods of using local waste materials as organic manures. The survey indicated that farmers are lacking in knowledge and did not value the importance of farm record keeping. Therefore, farm records were not available to provide sufficient information to construct a nutrient budget for each farm. Soils and herbage samples were collected in different places within the study areas. Soils were collected at 0-7.5 cm and 7.5-15 cm depths. These samples were chemically analysed and used in a glasshouse trial to test the growth response of white clover (T.Repens) to phosphate (P) and potassium (K) and sulphur (S) fertilizer additions. Low soil P test values were common, however analysis of the field sampled herbage did not confirm P deficiency. In the glasshouse trial, however legume growth was highly responsive to soil type, initial soil P status and added P fertiliser. Legume growth was non-responsive to application of K and S.Recommendations relating to farm record keeping, soils and herbage tests results, and alternative strategies to improve/maintain the soil fertility are discussed. Future research directions that should be taken to boost the production of pasture and beef cattle industry are also discussed.Item Land treatment of dairy-farm effluent using short rotation forestry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University(Massey University, 1999) Roygard, Jonathan K. F.Under the Resource Management Act (1991) New Zealand dairy farmers are required to dispose of dairy-farm effluent in such a manner as to have no adverse effect on the receiving environment. This study investigated the land treatment of pond treated effluent to short rotation forestry (SRF). The study involved both field trials and modelling work to assess sustainability of these systems in terms of nitrogen leaching to groundwater. A lysimeter study investigated 3 SRF species, 2 evergreen species of Eucalypts (Eucalyptus saligna, E. nitens) and a deciduous willow (Salix kinuyanagi) in the treatment of dairy farm effluent. Trees were grown in lysimeters (1.8 m diameter, 1.0 m depth) to enable measurement of water and nitrogen balances. A bare-soil treatment was used as a control. The application of dairy-farm oxidation-pond effluent totaled 218 g N lysimeter-1 (equivalent to 872 kg N ha-1) over 2 irrigation seasons (December 1995-June 1996 and September 1996-April 1997). Effluent was applied weekly during the irrigation seasons at a rate of 21 mm week-1. No effluent was applied during the winter period. The drainage period of the E. nitens was shorter than that of the S. kinuyanagi, and rates of leaching were respectively lower. Both these treatments leached for shorter periods than E. saligna. Leaching of the bare-soil treatment was consistently high throughout the experiment. Water use through evapotranspiration was found to have a large impact on drainage volume and timing. The trees were shown to improve effluent treatment because high evapotranspiration rates reduced the volume of leachate passing beyond the root zone. Further, uptake of nitrogen by the trees reduced the quantities of nitrogen available for leaching. In this study both E. nitens and S. kinuyanagi were more suitable for land treatment than the other 2 treatments evaluated. The low nitrogen concentration in the leachate under the S. kinuyanagi is the key criterion which determines the suitability of this tree species for land treatment of effluent. The low total loading of nitrogen to the groundwater of the E. nitens treatments is the key criterion in determining E. nitens suitability. Although the nitrogen concentrations in the leachate of the tree treatments were generally less than the bare soil treatments, they were still greater than the New Zealand drinking water standard (NZDWS) of 11.3 mg NO3- -N, during certain periods of the experiment. From the lysimeter experiment it was concluded that the leachate nitrogen concentrations might have been reduced if the amount of nitrogen applied in the effluent was reduced. Total production of above-ground biomass in the 2.5 years, based on the stocking rate of 4000 stems ha-1 was equivalent to 15.6, 30.6, and 21.3 Mg ha-1 yr-1 for E. saligna, E. nitens, and S. kinuyanagi respectively. Although scaling up biomass estimates from small plot trials and particularly lysimeters introduces associated errors, the estimates fell within the ranges measured elsewhere in New Zealand. The lysimeter study was complemented by the modelling of the water and nitrogen balances of SRF land treatment systems. Ultimately, the aim of the model was to investigate the effect of changes in management practices on sustainability in terms of nitrogen leaching of SRF systems treating dairy-shed effluent. The model selected for this purpose was a lumped parameter model (LPM). The water and nitrogen balances of the bare soil and E. nitens treatments were simulated with the model to determine the applicability of an LPM scheme to predict system behaviour. The model predicted, with broad agreement, the measured water and nitrogen balances of the lysimeter experiment. The model was then used to simulate the behaviour of a SRF plantation receiving dairy-shed effluent at a rate of 200 kg N ha-1 yr-1 over 27 years. This simulation predicted the occurrence of high nitrate concentrations in the leachate. This would be a limiting factor for the long term sustainability of such a system. A sensitivity analysis of the model was used to reveal the important parameters of water movement and nitrogen cycling that effect both nitrogen concentration and quantity in the leachate moving below the root zone. Water movement was most sensitive to root zone depth, effective rainfall, available water and crop water use. The nitrogen fate parameters with greatest effect on leachate nitrogen concentration and quantity were denitrification activity and volatilisation. Plant growth parameters of light utilisation efficiency, maximum leaf nitrogen concentration and specific leaf area strongly effected leachate nitrogen concentration and quantity. Mineralisation rates of the soil humus and the senescence rates of plant material also impacted on quantity and concentration of nitrogen leaching. The model's applicability as a decision support tool was demonstrated by examining the impact of various effluent loading rates on the leachate concentration and quantity. Based on leachate nitrate concentrations being on average lower than the NZDWS, the key finding was that the sustainable loading rate for the simulated system was found to be around 75 kg N ha-1 yr-1. The major finding of both the lysimeter experiment and the modelling study was the high nitrogen concentrations leaching from SRF dairy-shed effluent treatment systems. The LPM model clearly provides a platform from which to investigate many other possible scenarios of management to minimise the leaching of the high concentrations of nitrogen into the ground water.Item Developing sustainable soil fertility in southern Shan State of Myanmar : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2001) Tin Maung AyeLiterature review and a farm survey results indicated that the productive capacity of the Red Earths and Yellow Earths (Acrisols in FAO/UNESCO system) in Southern Shan State, Myanmar, continues to decline as poor, near-subsistence, farmers usually fallow-crop these soils and are unable, for economic reasons, to provide the necessary fertilisers and crop management strategies that could improve and maintain soil fertility. This thesis reports on investigations undertaken to determine ways in which the fertility of these soils can be improved in an economical and sustainable manner. A preliminary soil survey confirmed that soils of the Southern Shan State study area had low soil P status, low pH, low SOM (low reserves of N, P and S) and low base saturation, which are likely constraints to crop production on these marginal soils. A farmers' survey indicated farmers were aware of the P availability and soil acidity problems, however, they use low levels of N, P, K fertilisers, green manure and liming material because their economic margins were insufficient to buy expensive P fertilisers and liming materials. Preliminary glasshouse trials were conducted to establish the key soil fertility constraints. These trials included testing the P responsiveness of crops (pigeon pea (Cajanus cajan), rice bean (Vigna umbellata) and upland rice (Oryza sativa L)), the influence of liming materials on legume growth (black gram (Vigna mungo), cowpea (vigna unguriculata), kidney bean (Phaseolus vulgaris), lentil bean (Culinaris lentil), pigeon pea, soybean (Glycine max), stylosanthes (Stylosanthes quyanensis)), and the effectiveness of green manures for building SOM and P reserves in the Red Earths and Yellow Earths. The glasshouse trials confirmed that low P status is the factor most limiting to crops particularly legumes grown in the Yellow Earths. Upland rice, however, did not respond to added P suggesting that upland rice may not be a suitable test plant for evaluating the relative P effectiveness of fertilisers in the Red Earths and Yellow Earths. This pot experiment with the upland rice trial also demonstrated that indigenous Myanmar phosphate rock (MPR) and Farmyard manure (FYM) were ineffective P sources for raising soil plant-available P in the short-term. Local dolomite, however, was an effective liming material and when added with P enhanced the nodule formation of pigeon pea. Laboratory incubation studies showed that incorporating organic amendments (FYM, pigeon pea and upland rice residues) into the Red Earths and Yellow Earths significantly increased soil organic C, improved soil pH buffering, increased the total P content and increased labile-P fractions that could be used for plant growth. The Walkley and Black organic C determination can be used as a suitable 'low tech', portable method for the determination of organic C to monitor soil organic matter levels. Based on the results from the preliminary glasshouse trials, field trials were designed to establish relationships between P fertiliser form, application rate and soil P test levels for maize (Zea mays) and legumes (rice bean and black gram) grown in a Yellow Earth. In soils with initial Olsen-P values of approximately 8 kg P kg-1 soil, two maize field trials consistently indicated that near maximum yield (90%) of maize can be obtained by application of water-soluble P fertiliser (Triple superphosphate, TSP) at 40 to 50 kg P ha-1 in year one and reapplication of TSP at 25 kg P ha-1 in year two. Phosphate supplied as FYM, Tithonia diversifolia, Chinese partially acidulated phosphate rock (CPAPR) and Sechura reactive phosphate rock (SPR) were agronomically less effective as short-term P sources for maize than TSP, with TSP substitution ratio of 0.1, 0.17, 0.61 and 0.07 respectively at an application of 40 kg P ha-1 rate. A legume-wheat rotation field trial showed that rice bean (the legume) yield was significantly increased by the application of TSP at 40 kg P ha-1 plus local dolomite. Subsequently, rice bean plots fertilised with 40 kg P ha-1 as TSP produced the largest wheat grain yields in the Yellow Earth. In all trials the Olsen-P test was a suitable soil P test for providing an index of plant-available P. Olsen-P values at which optimum crop growth occurred (90% maximum yield) ranged between 30 to 40 mg P kg-1 in the Red Earths and Yellow Earths, depending on the season, plant age when harvested and crop grown. Use of the sulphuric acid acidulated CPAPR and elemental S (S°) with SPR confirmed that plant growth in the Yellow Earths was very responsive to sulphur application. Chinese PAPR can be used as a cost-effective P and S fertiliser to increase the crop yield in these Red Earths and Yellow Earths, particularly where S is also deficient. Use of local dolomite (2.5 t ha-1) in the field trials caused significant increases in soil pH in the first season and in the legume-wheat trials resulted in increases in legume yield. The research findings on soil P testing, alternative P sources and liming materials presented in this thesis are discussed in terms of the role they might have in the establishment of sustainable agriculture practice in Southern Shan State, Myanmar. Future research directions that should be taken to realise the productivity of these soils and farming systems are also discussed.