Showing papers by "Keith C. Cameron published in 2021"

Production, profit and nitrogen flows in irrigated dairy systems representing different industry development pathways: the Pastoral 21 experience in Canterbury

Abstract: Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional ...

The effect of polyferric sulphate treated farm dairy effluent and clarified water on leaching losses, greenhouse gas emissions and pasture growth

Abstract: A lysimeter experiment was conducted to investigate the environmental effects of applying farm dairy effluent (FDE) treated with a chemical coagulant (polyferric sulphate) to land. The coagulant wa...

Integrating Plantain (Plantago lanceolata L.) and Italian Ryegrass (Lolium multiflorum Lam.) into New Zealand Grazing Dairy System: The Effect on Farm Productivity, Profitability, and Nitrogen Losses.

Abstract: A two-year farm system study was conducted at Canterbury, New Zealand to evaluate the effects on farm productivity, profitability, and nitrogen (N) losses of integrating plantain (Plantago lanceolate L.) and Italian ryegrass (Lolium multiflorum Lam.) into a ryegrass and white clover (RGWC)-based dairy system. Three farm systems were compared: (1) a lower input RGWC-based system (LIRG) with stocking rate of 3.5 cow/ha, annual N fertiliser rate of 150 kg/ha, and imported feed level of 1.2 t DM/cow/year. Cows in the LIRG + PL system grazed a diverse mix of Italian ryegrass, perennial ryegrass, white clover, and plantain (60% of farmlet area), and a mixed sward of plantain-white clover (40% of farmlet area). The average annual herbage harvested was similar between LIRG + PL and LIRG (11.7 t DM/ha), but greater in HIRG (12.7 t DM/ha) with the increased N fertiliser rate. During the calving to dry-off period, the average imported supplement feed per ha was higher in HIRG (8.0 t DM) compared with LIRG (3.2 t DM) and LIRG + PL (3.7 t DM). Average milk solid production (MS; fat + protein) was similar in LIRG + PL (1640 kg/ha) and LIRG (1622 kg/ha), but greater in HIRG (2130 kg/ha). Estimated profitability (NZD/ha) at milk price of NZD 6.5/kg MS was 10% greater for HIRG than LIRG + PL and LIRG, and similar (<1.5% numerical difference) between LIRG + PL and LIRG. The average estimated annual N leaching loss from the LIRG and LIRG + PL was 31% and 56% less than the loss from the HIRG. These large reductions in N leaching loss were achieved without a large decrease in profitability (i.e., LIRG and LIRG + PL compared to HIRG). In addition, the estimated reduction in N losses from the LIRG + PL system compared to LIRG suggests that an Italian ryegrass + plantain-based dairy system is a viable strategy to reduce the environmental footprint while maintaining farm profitability. However, the environmental benefits of plantain and Italian ryegrass estimated in this study require further confirmation through direct measurements at full farm level.

Discovery of a new method to reduce methane emissions from farm dairy effluent

Abstract: The New Zealand Government requires gross emissions of biogenic methane (CH4) to be reduced to 10% below 2017 levels by 2030. However, the amount of CH4 emissions reported in the ‘Manure Management’ category of New Zealand’s Greenhouse Gas Inventory has increased by 123% since 1990. The purpose of this research was to determine the effect of treating farm dairy effluent (FDE) with polyferric sulphate (PFS) on CH4 emissions. The effect of treating FDE with PFS on CH4 emissions was measured at four scales: (i) 1-L gas jars in the laboratory, (ii) 1.1-m-deep × 150-mm-diameter pipe microcosms in the laboratory, (iii) large 3.4-m-deep × 0.47-m-diameter pipes on-farm, and (iv) 2-m-deep × 8.4-m-diameter (100,000 L) commercial effluent storage tanks on a farm. Gas emissions were captured by repeated discrete sampling and CH4 concentrations were determined by gas chromatography. We discovered that treating FDE with PFS at an average rate of 220 mg Fe L−1 of FDE reduced CH4 emissions by up to 99% and that this effect continued for an extended period of time (up to 2 months) after treatment. The PFS treatment also reduced CO2 emissions by approximately 50% and reduced hydrogen sulphide emissions. PFS treatment resulted in a small increase in nitrous oxide (N2O) emissions, but these emissions were very low and only represented < 3% of the total CO2-e greenhouse gas emissions from the treated FDE. A new method to reduce CH4 emissions from farm dairy effluent by up to 99% has been discovered.

Assessment of spatial and temporal variability in soil moisture using multi-length TDR probes to calibrate Aquaflex sensors

Abstract: Despite subtle variations in soil moisture (SM) across a paddock, irrigation scheduling in New Zealand dairy farms is solely based on the SM monitored at a single location, primarily using an Aquaflex soil moisture sensor at a specified root depth. This study aimed to address this issue by assessing the “effective” root depth of a pasture, calibrating the Aquaflex soil moisture sensor and evaluating the spatial and temporal variability of SM. Twenty non-weighing lysimeters and 1 Aquaflex with 2 sensors installed 125-m away from the lysimeters on the same paddock were utilized for the study. TDR probes with 200-, 500- and 900-mm lengths were installed vertically adjacent to the Aquaflex and the lysimeters for monitoring spatio-temporal variability in SM, and calibrating the Aquaflex. A dry down experiment was performed for investigating the root depth of the pasture. All TDR probes responded to wetting and drying events, with varying SM measurements both vertically and horizontally, due to variations in soil type at different locations, indicating a need of SM monitoring at different locations in the paddock for irrigation scheduling. There was a strong linear relationship between the Aquaflex and TDR probes readings, which can be used to calibrate the Aquflex and improve its reliability for measuring soil moisture and in turn irrigation needs. Over the dry down period, out of the total moisture change in the 0–900-mm soil profile, 96% was contributed by 0–500 mm, indicating that the significant root depth of the pasture lies on the top 500-mm soil profile. Findings of the study can contribute to better irrigation scheduling and to conserve water.