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    Comparison of maize silage and traditional forage crops in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Manawatū Campus, New Zealand
    (Massey University, 2022) Thant, Aung Myo
    Cattle wintering systems using crops including grazing kale, swede, and fodder beet crops in situ have resulted in soil and water quality deterioration. Nitrate leaching is the most common problem due to the high deposition of urine N driven by excess N intake. Alternative cropping systems offer a potential solution to reduce these environmental problems while maintaining or maximising productivity. We proposed maize silage as an alternative crop because it has high yield potential, flexible feeding requirements, compliments the nutritive value of pasture, and is potentially suitable for more regions in New Zealand in the future due to climate change. However, research needs to determine whether maize silage yield, feed quality and potential nitrate losses during production and utilisation means it is a viable alternative to in situ grazed forage crops in these areas. Field experiments were conducted at Massey University, Tokoroa and Kiwitea to determine forage yield and feed quality, management effects and site differences in 2018/19 and 2019/20. Crop yields and forage N content were utilised to simulate urine N loads from the feeding of these forage crops. The excreted N loads were analysed in APSIM (Agricultural Production Systems sIMulator) to predict nitrate leaching losses. Maize produced significantly higher yields compared with the winter forage crops at all Massey University trials while producing competitive yields at Tokoroa and Kiwitea. Yields ranged from 10,940 to 30,417 kg DM/ha for maize whilst wide and lower yield ranges were observed for the winter forage crops (4,579 to 22,928 kg DM/ha). Irrigation increased yields of forage crops by 29-63%. Similarly, nitrogen fertiliser increased yield by 30%, on average. The faster canopy development of maize has the advantage of intercepting more radiation in summer and suppressing weeds, contributing to greater growth and yield despite a shorter crop season. All forage crops produced forage with good metabolisable energy content (MJ/kg DM); higher values in swede (10.1-14.5) and fodder beet (10.8-14.9) whereas intermediate values in kale (8.9-12.7) and maize (9.9-12.2). However, maize was the highest energy-yielding crop, ranging from about 200-316 GJ/ha while other crops varied from 34 to 217 GJ/ha. Protein content in kale (7.5-16.6% DM) and swede (11.4-18.2% DM) were adequate for non-lactating cows whereas maize (5.4-9.2% DM) and fodder beet (7.6-11.2% DM) were lower than recommended protein levels for dairy cows but offering an opportunity to reduce urinary N excretion. Maize also had recommended fibre content. With higher sugar contents, swede and fodder beet were poor in fibre sources, potentially prone to rumen acidosis unless considered mixed diet with high fibre feed. APSIM modelling indicated that maize would produce the lowest urine N output while swede the highest in simulated feeding. Accordingly, N loads/ha was higher for winter forage crops especially when good yields were produced. When common feeding practices were considered, i.e., off-paddock maize feeding (no urine N deposition) and on-paddock grazing of winter forage crops (high urine N deposition), simulated nitrate losses from maize cropping systems were the lowest. Predicted nitrate losses were 21 and 32 kg N/ha for maize under irrigated and non-irrigated conditions. A ryegrass cover crop further reduced simulated nitrate losses by 20-30%. Predicted nitrate losses for fodder beet, kale, and swede crops were 126, 162, 154 kg N/ha under irrigated conditions and 72, 201, 199 kg N/ha under non-irrigated conditions, respectively in grazing systems.
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    The effects of late nitrogen in the yield and quality of milling wheat : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Agronomy at Massey University
    (Massey University, 1992) Millner, James
    The quality of wheat milled to produce flour for leavened bread is related to its protein content. The presence of specific proteins in milling wheat gives dough its elastic properties and dertermines baking quality. Good quality wheat will produce loaves with high volumes and a fine crumb texture. It is known that wheat cultivars differ in their ability to produce good quality bread through differences in the composition of their protein. In cultivars of good quality, the greater the protein content, the better the quality of bread produced. The Manawatu Mills Limited, Palmerston North varies the price it pays for milling wheat according to cultivar and protein content. Premiums can be obtained by increasing grain protein content. This presents local wheat growers with the financial incentive to improve the yield and quality of their crops. To investigate the feasibility of using late applications of nitrogen fertiliser to increase the protein content and yield of milling wheat three trials were carried out at different sites during the spring and summer of 1989/90. These sites were at Kairanga, Almadale and Waituna West in the Manawatu region using the cultivar Rongotea. They were chosen to provide a range of environmental conditions, particularly temperature, over which to test the effect of nitrogen fertiliser on protein content. To achieve different temperature regimes, these sites are situated at low, medium and high altitude. It has been suggested that temperature over the grain-fill period can influence both protein content and composition of wheat, which in turn influences its ability to produce good quality bread. Four different rates of nitrogen fertiliser were applied just prior to the boot stage. These were 0, 20, 40 and 80 kg N/ha. There were significant differences in grain yield amongst sites with Kairanga achieving 6.4 tonnes/ha, Almadale 5.9 tonnes/ha and Waituna West 6.8 tonnes/ha. These yields were above the long term district average. Grain yield responded to late nitrogen at Kairanga and Waituna West. Yields increased from 6.1 to 6.9 tonnes/ha at Kairanga and from 6.4 to 7.2 tonnes/ha at Waituna West as application rates increased from zero to 80 kg N/ha. Any potential yield response at Almadale was suppressed due to an infection of the root rot fungus, 'take-all'. The yield response at Kairanga resulted from an increase in grain weights whereas at Waituna West it resulted from an increase in ear numbers at harvest. At both responsive sites late nitrogen delayed conopy senescence. Protein contents also varied significantly amongst sites and in response to the application of nitrogen fertiliser. Protein content (14% moisture basis) ranged from 8.87 to 10.87% at Kairanga, from 10.35 to 11.28% at Waituna West and from 12.97 to 13.69% at Almadale as application rates increased from zero to 80 kg N/ha. The differences in protein levels obtained from different sites resulted in a considerable variation in baking quality. Samples from eight plots from each site were sent to the Wheat Research Institute, Christchurch, for test baking. Average bake scores were 19 at Kairanga, 21 at Waituna West, and 26 at Almadale. There was a strong, positive relationship between bake score and grain protein content amongst these samples. A convenient measure of baking quality, the sodium dodecyl sulphate test, was used to estimate baking quality of each plot. This allowed the relationship between baking quality and grain protein content to be identified for each site. The relationship between protein and baking quality differed between sites, being much stronger at Kairanga than at Almadale and Waituna West. The relatively poor relationship between protein and baking quality at Waituna West and Almadale can be partly explained by the limited range of protein contents resulting from treatment effects, particularly at Almadale. There was evidence that site had influenced the relationship between protein content and baking quality. At Kairanga and Waituna West late applications of nitrogen fertiliser significantly increased both grain yield and protein content. The yield increases, combined with the price premiums for increased protein, meant that it would have been profitable to apply late nitrogen. At Almadale there was no yield response and the protein response was limited, making late applications of nitrogen uneconomic. Pest and disease pressure at Almadale reduced yield, contributing to grain protein content being above the point where premiums are available. It was concluded that it can be economically feasible to use late applications of nitrogen on crops which have a high potential yield. Factors limiting yield, such as pests, diseases and moisture stress, will limit any potential benefit.
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    Kiwifruit (Actinidia spp.) vine and fruit responses to nitrogen fertiliser applied to the soil or leaves : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Fruit Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2013) Morton, Allan
    Dry matter concentration (DM%) of the fruit is a primary indicator of quality for kiwifruit (Actinidia spp.), lower levels being associated with inferior tasting fruit. Carbohydrates and particularly starch, are the main component of dry matter in the fruit of Actinidia spp. In plants, N fertilisation can reduce carbohydrate levels and increase succulence. Therefore high levels of N fertilisation could reduce fruit DM% by reducing its dry matter accumulation and increasing its water content. High rates of N fertiliser applied to kiwifruit vines (A. deliciosa) over four seasons tended to produce larger fruit (5% heavier on average over the four seasons) mainly due to increased water content with less effect on total dry matter contents. Consequently DM% was reduced from an average over the four seasons of 16.1% in the unfertilised (control vines) to 15.6% in fruit from the N fertilised vines. However, vegetative vigour in terms of the weight of shoots was increased by up to 150% by N fertiliser. Biostimulants applied as foliar sprays and surplus water supplied to the soil appeared to alter the balance between dry matter and water accumulation in the fruit in a similar way to soil-applied N fertiliser. It is concluded that increases in fruit size induced by N fertilisation, biostimulants, surplus water, and even girdling are at least partly due to the creation of increased hydraulic gradients between the vine and fruit leading to increased water uptake by the fruit. Other effects on fruit of high rates of soil-applied N fertiliser included reduced ascorbic acid, oxalate, and epidermal phenolics. Reductions in levels of these compounds and the generally increased succulence of N fertilised vines may increase the susceptibility of the vines to pests and diseases. In contrast to soil-applied N, foliar sprays of N applied during early fruit development stages increased fruit growth with no apparent effect on vegetative vigour. Aqueous solutions (1% w/v) of both urea and potassium nitrate were effective forms of N for foliar application and could increase fruit fresh weight by between 6 and 10% depending on the season and number of applications. It is estimated that the use of foliar-applied N during early fruit development could represent an increase in crop value of between $3600 and $15,000 per hectare depending on size and yield. Foliar-applied N shows promise as an alternative way to manage the N nutrition of kiwifruit with favourable effects on fruit quality since dry matter accumulation in fruit tended to increase proportionately with increased water uptake. Foliar application of N can also avoid some of the adverse environmental effects associated with the soil application of soluble N fertilisers.