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    Effects of no-tillage and subsoil loosening on soil physical properties and crop performance : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Soil Science at Massey University
    (Massey University, 1998) Hamilton-Manns, Mark
    Much of New Zealand's lowland agriculture integrates animal and crop production on poorly drained, easily compacted soils. Over the years, conventional cultivation has given rise to degraded soil structure on many farms. No-tillage has been shown to avoid many of these problems but the question remains: "Where soils are compact, what combination of deep tillage and/or drainage systems and no-tillage allow for the most efficient transition from conventional cultivation to no-tillage crop establishment?" The objective of this study was to ascertain if soil properties, and crop (Brassica campestis x Brassica napus cv "Pasja" followed by wheat Triticum aestivum cv "Kohika") establishment and yield on land converted from a conventionally tilled system to a no-tillage system could be improved by various subsoiling and mole plough operations. Plots on a Milson silt loam (Argillic Perch-Gley Pallic Soil) (Typic Ochraqualf) were paraplowed (PP), straight-legged subsoiled (SL), mole ploughed (M) or were left as non-subsoiled controls (C) in the autumn of 1997. Forage brassica was then sown with a Cross-Slot™ no-tillage drill. Wheat was established on the same plots with the same no-tillage drill in the spring of 1997. Subsoiling initially reduced soil strength by a significant amount. Shortly after subsoiling cone indices showed disruption to 300 mm with PP, 350 mm with SL and 100 mm with M. At the same time, approximately 20% of profile cone indices from subsoiled treatments were greater than 2 MPa, compared to approximately 52% for C and M. At 267 days after subsoiling, PP continued to have lower cone index values than C and M. Subsoiling initially reduced bulk density. When measured in May, the bulk density of PP plots was significantly lower than SL, M and C although reconsolidation in all plots was observed in February 1998 after the wheat was harvested. Air permeability in PP, SL and M was significantly greater than in C. Despite the differences in soil strength and bulk density (but not air permeability), subsoiling and mole ploughing did not produce differences in plant populations or yield for either the winter brassica or spring-sown wheat crops. The lack of any differences for brassica crop performance criteria were in spite of the vertical rooting depth being greater in the PP treatment. The lack of differences in plant establishment and yield was thought to be due to the relatively dry autumn and winter soil conditions and the use of the Cross-Slot™ no-tillage opener which is reported to be tolerant of variable soil conditions.
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    Aspects of seed transfer within a direct drilling coulter (opener) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Agricultural Mechanisation at Massey University
    (Massey University, 1982) Ritchie, William Rowlan
    A number of laboratory and field experiments were conducted in order to identify and quantify seed and seedling spacing variations produced by an experimental direct drill. Seed contact with both stationary and moving components of the coulter assembly was considered to contribute to the increased variability of seed spacing that resulted from the positioning of a chisel direct drilling coulter beneath a "Nodet Gougis" seed selection mechanism. Alternatives for transferring the seeds from the seed selection mechanism to the soil were considered. The simplest of these alternatives, a seed-transfer tube, was tested in a number of different shapes and positions. It was found that the seeder required modifications to its release characteristics in order to satisfactorily incorperate the tube transfer system. A number of deflector plates were fitted to the seeder to control seed release trajectory. A 40 degree seed deflector plate was found to produce a seed path that was most compatible with a straight vertical seed-transfer tube. A video recording technique was used to assess the effects of seeder modifications on seed release trajectory. The modified seeder and the tube transfer system were combined with the chisel direct drilling coulter, and seed spacing performance was retested. Seed spacing variability was found to be considerably less than with the original experimental drill in the laboratory, although field performance was not improved to the same extent. It was considered that this effect may have been attributable to the effects of soil flow with the direct drilling coulter and the manner with which the seed was released into the soil, which differed with the tube system compared with the unmodified coulter tested initially.
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    Effect of method of tillage on loss of carbon from soils : 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, 2012) Ghatohra, Amandeep Singh
    Soils represent the largest terrestrial carbon (C) pool. Different tillage practices have been shown to result in variable losses of soil C. Among these, No-tillage is regarded as an effective management practice for conserving SOC and reducing soil CO2 emissions. Overseas research shows that No-tillage practice could reduce CO2 emissions by approximately 3 Mg CO2 ha-1yr-1. Quantitative information comparing soil CO2 emissions with No-tillage and conventional tillage is limited in New Zealand. Furthermore, little quantitative information is available on the effect of soil and climatic conditions in modifying these emissions. This Ph.D. study evaluated the potential for Cross Slot® No-tillage cultivation to reduce CO2 emissions from cropped soils in New Zealand conditions. A series of preliminary experiments were conducted to establish a suitable chamber method to collect and measure CO2 emissions from soil. The alkali trap method was selected for use in traditionally cultivated agricultural soils. Another experiment was conducted to test whether pressure fluctuations caused by wind velocity differentially influence soil CO2 emissions from conventionally and Cross Slot® No-tillage cultivated soils. Carbon dioxide emissions from conventionally cultivated soils rapidly equilibrated to the onset of lower (negative) pressure, whereas CO2 emissions from No-tillage soils took longer to equilibrate. Experiments on the potential savings of soil C with Cross Slot® No-tillage cultivation (NT) compared to simulated tillage, measured in the laboratory showed reduced (between 113 and 393 kg CO2-C ha-1) CO2 losses in three out of four soils. This reduction in CO2 losses was further verified with measurements made for one of the soils at a field site during autumn and summer seasons. Overall the results of field studies suggest that Cross Slot® No-tillage cultivation reduced ~3.0 Mg CO2 ha-1 compared with rotary tillage for combined autumn and summer sowings i.e. two cultivations. A subsequent laboratory incubation study assessed CO2 loss with different levels of residue addition to the four soils used in the previous laboratory and field experiments. A number of labile C fractions extracted from these soils were measured in an attempt to predict CO2 losses. These did not show any relationship with the CO2 respired during the incubation period. It was, therefore, not possible to develop a soil test to predict CO2 losses using these extractions. Modelling laboratory CO2 respiration data for predicting the CO2 losses from conventional and No-tillage soils was explored using relationships between short-term CO2 respired and total CO2 loss. The model developed from laboratory incubations was further improved with parameterising the soil temperature and moisture effects. The temperature and moisture sensitive model was used to predict the CO2 emissions measured during the summer season. The model precisely predicted the amount of C lost from No-tillage soils but the amount predicted for rotary tilled soils was 30 per cent less than the amount of C that was lost in the field. Moreover, the model predicted C loss was higher for the No-tillage soils than the rotary tilled soils which was contradictory to the findings from the field study. Therefore, further work is required as the data obtained during this Ph.D. study was insufficient to provide, or develop a model that could be used to predict CO2 loss from conventional and No-tillage cultivation in New Zealand soils.
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    Row spacing and seeding rate interactions in perennial ryegrass and tall fescue swards established by direct drilling (no-tillage) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand
    (Massey University, 1995) Praat, John-Paul
    Direct drilling is a popular and cost-effective method of introducing new, more productive pasture species into existing pasture on farms in New Zealand. The technique conserves both time and money, reduces moisture loss and the risk of soil erosion and offers some management benefits in intensive agricultural systems. Seed drills in New Zealand commonly used for pasture establishment sow seeds in rows at 150 mm centres. While this is an acceptable row spacing for cereal crops, eg. barley and wheat, closer row spacing has been proposed for establishing pastures. However, little research has been carried out to determine optimal row spacing or seeding rates. The benefit of cross-drilling with two passes of the drill, which is a practice thought to overcome the perceived inadequacies of 150mm row spacing, is also uncertain. This study was designed to investigate the effects of row spacing and cross-drilling, and the relative importance of plant population per unit area and per unit length of drill row on pasture establishment and development. Single pass sowing, at both 150 and 75mm row spacings together with cross-drilling were compared in an autumn sown field experiment. Two species of contrasting establishment vigour, perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) and two seeding rates (12 and 23 and 17 and 31 kg ha-1 for perennial ryegrass and tall fescue respectively) were also compared. The trial was grazed by dairy cattle throughout the measurement periods. Emergence of 84 and 71 % of sown perennial ryegrass and tall fescue seed respectively, resulted in establishment of approximately 400-500 and 700-800 seedlings m-2 for medium and high seeding rates respectively for both species. Two years after sowing, medium to high seeding rates offered no advantage in terms of weed suppression or yield compared with low seeding rates. Cross-drilling offered no advantage for either species. Total herbage yield and the proportion of sown species was the same for perennial ryegrass and tall fescue established in either cross-drilled or 150 mm rows. This was the most important result, as far as the farmer is concerned, with potential cost savings of up to $100 per hectare by not carrying a second pass of the seed drill required for cross-drilling. The establishment performance of tall fescue in terms of herbage mass and suppression of weeds in the sward was initially improved with closer row spacing. These benefits were not apparent for perennial ryegrass. The advantage gained for fescue from reduced row spacing declined with time and by the second spring after sowing no difference was apparent between 150 and 75mm row spacing treatments. Thus, overall, drilling method had only a minor influence on botanical composition. Tall fescue was slower establishing and had more clover and weed in the sward compared with perennial ryegrass. This contrast in growth revealed the subtle influences of drilling method and seeding rate on pasture composition. A second trial, sown in the subsequent autumn, investigated the use of nitrogen with tall fescue at the time of sowing in both single pass and cross-drilling. The results supported those found for the effects of drilling pattern in the first trial. The use of nitrogen fertiliser in the damp, cool conditions of late autumn did not benefit sward development. Emergence of tall fescue was poorer at this time. In contrast to the results of Trial 1, increasing the seeding rate resulted in increases in initial seedling population and improved the performance of tall fescue. There was a higher proportion and herbage mass of sown species in the sward sown at the higher seed rate. This suggests that higher seeding rates may be required for tall fescue as conditions at sowing become cooler. However, the early advantage from the higher seeding rates was not apparent 10 months after sowing. Clover emergence was low at 46 and 52% of sown viable seed for the first and second trials respectively. However, a clover seedling population in excess of 150 plants m-2 was established in both trials which proved to be an adequate population for development of productive pasture. Drills designed for sowing aggressive species such as perennial ryegrass need not incorporate the option of reducing row spacing from the common 150mm with the subsequent cost disadvantages. However, the option of reduced row spacing may be appropriate for drills designed for sowing less vigorous alternative species such as tall fescue. Increased seeding rates and cross-drilling should not be necessary for successful establishment of a productive pasture sward of temperate species. This leads to improvements in efficiency of seed drill operation in the field.