Conference Papers
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Item COMPARATIVE EVALUATION OF CONTROLLED RELEASE FERTILISERS FOR NITRATE LEACHINGRaveendrakumaran B; Grafton M; Jeyakumar P; Bishop P; Davies C; Christensen, C; Horne, D; Singh, RA lysimetric study was carried out with an objective of evaluating the leaching behaviour of different fertilisers on spinach growth on Manawatu sandy soil. The fertiliser treatments applied were urea, two controlled release fertilisers called ‘g’and ‘SmartN’ at the rates of 50 kg N/ha (50N), 100 kg N/ha (100N) and 200 kg N/ha (200N). The 200 kg N/ha urea application was made in 10 split doses at a rate of 20 kg N/ha in 7-day intervals, whereas 200N application of ‘g’ and ‘SmartN’ were made twice at a rate of 100 kg N/ha at the time of planting and six weeks after planting. The control treatment did not receive any fertiliser application (0N). The application of Urea and ‘g’ at all rates except ‘g’-50N produced significantly higher nitrate leaching losses (19.8 to 27.7 kgN/ha) compared to the control (9.1 kgN/ha), while SmartN at all rates produced no significant increase in nitrate leaching. The total nitrate leached per ton of dry matter production was significantly reduced by the application of N fertilisers compared to the control (135.1 kgNO3 - -N/MgDM). On an average, 16.4 kg NO3 - -N/MgDM was leached from the fertilised treatments. Dry matter production increased at 200N application rates with all three fertilisers, but urea-200N produced the highest dry matter yield of 2377 kg/ha. In conclusion, frequent split applications of urea (urea - 200N) increased dry matter yield thereby significantly reduced nitrate leaching.Item STUDY THE INFLUENCE OF SOIL MOISTURE AND PACKING INCREMENTAL LEVEL ON SOIL PHYSICAL AND HYDRAULIC PROPERTIES(14/07/2020) Gunaratnam A; Grafton M; Jeyakumar P; Bishop P; Davies C; McCurdy M; Christensen, C; Horne, D; Singh, RReconstructed soil packing is an alternative for monolithic soil columns in lysimeter studies. The excavated soil is packed in uniform layers to represent the natural soil conditions. Reconstructed soil packing alters the physical properties, including bulk density and porosity, thus can distort the hydraulic properties of the soil, so consistency of the method used is critical. Therefore, the selection of a suitable packing method is imperative. This preliminary study comes under the broad research programme: “developing and testing new fertilizer formulations in lysimeters”. This work was aimed to study the effect of incremental packing methods on the hydraulic properties of soil to select the best combination for testing fertilizers. The selected soil matrix for this lysimeter study was composed of 10 cm topsoil and 30 cm washed builders’ sand. For this study, four different soil packs were trialled in lysimeters with the combination of two soil moisture conditions (dry/damp and wet) and two packing depth increments (5 and 10 cm). The flow rate and saturated hydraulic conductivity were measured. Subsequently, several pore volumes of water (around 5 – 6) was allowed to pass through the soil column and the soil subsidence level was measured for each packing method. Both soil moisture condition and packing increment level have influenced the flow rate and saturated hydraulic conductivity of the soil matrix. The saturated hydraulic conductivity of the dry-5 cm, dry-10 cm, wet-5 cm and wet-10 cm packing were 3.99, 6.70, 3.56 and 6.53 cm hr- 1 , respectively. Soil subsidence was also influenced by both the soil moisture condition and increment level. The highest soil subsidence was exhibited by dry-10 cm packing (13 mm) and lowest by wet-5 cm (2 mm) (p<0.05). This preliminary study showed that both moisture condition and increment level influence the soil hydraulic property and compaction level. Further study needs to be conducted to understand the influence of soil moisture and incremental level on other physical and hydraulic properties of soil packing.Item Characterization traffic induced compaction in controlled traffic farming (CTF) and random traffic farming (RTF) - A multivariate approachRaveendrakumaran B; Grafton MC; Jeyakumar P; Bishop P; Davies CE; Horne, D; Singh, RA field scale experiment was carried out in Pukekohe in 2020 under an annual grass crop season to characterize the subsoil compaction in controlled traffic farming (CTF) and random traffic farming systems (RTF). Soil penetration resistance (PR) measurements were taken in each field using a cone penetrometer fitted with a 100 mm2 60° top angle cone. Multivariate analysis was performed to identify penetration resistance by depth through cluster analysis and principal component analysis (PCA). Repeated measures ANOVA was performed on the penetration data using the mixed model procedure to determine the treatment effects. In RTF, the penetrometer values increased more rapidly with depth resulting in higher values being recorded from 20cm compared to CTF. In contrast, it was greater in CTF than in RTF at the subsurface (55-60cm). The differences in PR declined beyond 55cm depth at both sites. All depths showed that differences in soil PR were most apparent in the 5-40cm depth, with significant differences between CTF and RTF (P<0.0001). This shows that traffic management at both CTF and RTF sites caused significant changes in the 5-40cm depth. However, there were no differences in PR between CTF and RTF below 40cm and at 0-5cm depth (P >0.05) showing that the soil layers were homogeneous in both systems beyond 40cm depth. The propagation of subsurface compaction was identified at the deeper layer (40-60cm) in CTF systems whereas it was identified from shallower depths (25-55cm) in RTF system.Item ASSESSMENT OF NITROGEN FERTILIZERS UNDER CONTROLLED ENVIRONMENT – A LYSIMETER DESIGN(12/04/2019) Gnaratnam A; McCurdy M; Grafton M; Jeyakumar P; Bishop P; Davies C; Currie, L; Christensen, CThis paper introduces a closed system lysimeter design to measure fertilizer performance on ryegrass. The lysimeter will measure plant mass growth, gas emissions and leachate in a controlled climate environment based on a long term 90 day spring climate from the Taranaki. A range of commercial fertilizers will be compared to bespoke fertilizers manufactured under this project. This work, although undertaken in laboratory conditions will help quantify the impacts of nitrogenous fertilizers on the environment by mimicking actual conditions in a controlled setting. The study should provide data on the effectiveness of novel fertilizers manufactured within the programme; and other slow and controlled fertilizers, in reducing nitrogen leaching and greenhouse gas (GHG) emissions on pasture. Nitrogenous fertilizers readily leach as nitrates are highly soluble and GHG are emitted through volatilisation of ammonia and nitrous oxide. Reduced leaching and volatilisation increases fertilizer efficiency as less is wasted and more is attenuated in the plant. The aims of the research are to increase the effectiveness and efficiency of nitrogen fertilizer use in New Zealand. This should benefit farmers by reducing the amount of fertilizer applied, ideally reducing fertilizer cost, or at no extra cost by improved plant attenuation. This would also have an environmental benefit through reduced leaching and GHG emissions.
