Benchmarking best practice for irrigation productivity in Canterbury Dairy Farming

Abstract

Irrigation is an integral component of Canterbury dairy farming to produce reliable summer pasture production to support high performing dairy cows. Within the Canterbury region there is becoming increased pressure over the allocation and use of the finite resource that is fresh water. This study investigated the levels of production (milksolids, MS) from irrigation (megalitres, ML) which were being achieved on what were thought to be ten of the best farms in the Canterbury region in terms of converting irrigation water into milk production. From the analysis of case study information for the ten farms involved, benchmark figures for production from water use were developed along with the associated costs of irrigation water. The highest level of irrigation productivity over three years was 348 kg MS/ML of irrigation or 139 kg MS/ML of total water (irrigation + rainfall); this was on the Lincoln University Dairy Farm (LUDF). Centre pivot irrigated farms had the greatest level of productivity from water use at 106 kg MS/ML of total water followed by rotary boom and border dyke irrigated farms at 87 and 78 kg MS/ML respectively. Target levels of irrigation productivity for Canterbury dairy farms derived from the three best performing farms in this study should be 100-120 kg MS/ML of total water when allowing for the impact of purchased feed (including winter grazing). Increased irrigation water use resulted in a subsequent decrease in productivity in terms of milksolids per megalitre of irrigation. A strong relationship also existed between drymatter harvested and subsequent milksolids production per unit of water; an iii approximate 1% increase in drymatter harvested per hectare resulted in a 2.5% increase in milksolids production from total water used. The average cost of applying one megalitre of water across the 10 farms was $35 although this price per megalitre ranged from $60 for pivot, $53 for rotary boom and $7 for border dyke irrigation. When including the cost of capital (9% interest on the purchase cost of system), the cost of water increased to $116 and $85/ML for pivot and rotary boom irrigation respectively and $34/ML for border dyke irrigation. Operating profit (described as earnings before interest and tax, EBIT) was only able to be gathered accurately for three of the farms in this study with levels ranging from $233/ML to $671/ML of irrigation. There is scope for more work into establishing the levels of profitability being achieved on best practice farms and could be a useful set of data in the future. Two components for potential improvement of irrigation productivity on Canterbury dairy farms are increased soil moisture monitoring to reduce irrigation water applied and the upgrading of irrigation systems to reduce irrigation round lengths. A reduction in the interval between irrigation events will allow farmers to suspend irrigating when climatic conditions are favourable and begin again with the whole farm covered rapidly, preventing potential losses in production.