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Publication Date

1981

Description

In the desert climate of northern Mexico ground-water resources are being exploited in forage production for the dairy in• dustry. As rest-water levels are currently falling by 1. 75 m annually, there is urgent need to examine the water-management effi­ciency index (WEI) of present forage cropping patterns and to replace the less efficiently managed species without decreasing the overall regional mean milk production of 141/cow/day. The present study describes the approach taken to achieve this goal and the implications of the approach for increased water-management efficiency in this region. Data are drawn from (1) on-farm surveys of 68 forage and 26 dairy-production units, (2) on-station feeding trials, and (3) small-plot studies. The principal analysis is the efficiency of transformation of water into forage DM and milk. Annual forages (corn, sudangrass, Italian ryegrass, oats) were compared individually with alfalfa in sole-forage diets for milk production. Although milk yields were lower with the alternative forages, ratios of WEI to milk and feed costs/kg milk produced were improved in every case. Milk produc­tion/cow did not decrease below the regional mean. The current regional cropping pattern (1978) produces 1.6 million tons of green forage with an approximate WEI of 0.83 kg DM/m3 water. By replacing alfalfa (67% cropped area) with larger proportions of annual forage, WEI could be increased by 12 % , with reduction of water input by only 19 % . However, great uniformity of water requirement during the year makes a pat­tern based on annual forages attractive in a region where mean well extraction rates are 35 }/second. Regional basin-irrigation technology is considered to be the greatest constraint to water-use efficiency. A 25 % decrease in water depth/application ( officially estimated at 0.16-0.20 ha-m) would increase WEI by 49 % to 1.24 and decrease ground-water exploitation by 39%. As measurements determined the realistic value to be 0.22 m, the potential saving is even greater. 􀅧tis concluded that savings of this magnitude would have a significant impact on the future prosperity of the region.

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Alternative Forage-Production Patterns for Dairy Cattle Under Conditions of Limited Water Supply in Northern Mexico

In the desert climate of northern Mexico ground-water resources are being exploited in forage production for the dairy in• dustry. As rest-water levels are currently falling by 1. 75 m annually, there is urgent need to examine the water-management effi­ciency index (WEI) of present forage cropping patterns and to replace the less efficiently managed species without decreasing the overall regional mean milk production of 141/cow/day. The present study describes the approach taken to achieve this goal and the implications of the approach for increased water-management efficiency in this region. Data are drawn from (1) on-farm surveys of 68 forage and 26 dairy-production units, (2) on-station feeding trials, and (3) small-plot studies. The principal analysis is the efficiency of transformation of water into forage DM and milk. Annual forages (corn, sudangrass, Italian ryegrass, oats) were compared individually with alfalfa in sole-forage diets for milk production. Although milk yields were lower with the alternative forages, ratios of WEI to milk and feed costs/kg milk produced were improved in every case. Milk produc­tion/cow did not decrease below the regional mean. The current regional cropping pattern (1978) produces 1.6 million tons of green forage with an approximate WEI of 0.83 kg DM/m3 water. By replacing alfalfa (67% cropped area) with larger proportions of annual forage, WEI could be increased by 12 % , with reduction of water input by only 19 % . However, great uniformity of water requirement during the year makes a pat­tern based on annual forages attractive in a region where mean well extraction rates are 35 }/second. Regional basin-irrigation technology is considered to be the greatest constraint to water-use efficiency. A 25 % decrease in water depth/application ( officially estimated at 0.16-0.20 ha-m) would increase WEI by 49 % to 1.24 and decrease ground-water exploitation by 39%. As measurements determined the realistic value to be 0.22 m, the potential saving is even greater. 􀅧tis concluded that savings of this magnitude would have a significant impact on the future prosperity of the region.