Date of Award:

1974

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Advisor/Chair:

DeVere R. McAllister

Abstract

A study was made to compare the protein and forage yield and root dry weight data of five pasture mixtures as influenced by two clipping frequencies (28 and 35 day clipping intervals), three irrigation intervals (1 inch every 5 days, 2 inches every 10 days and 4 inches every 20 days) and four levels of nitrogen fertilization (0, 50, 100, and 200 pounds per acre). The study was conducted at the Greenville Farm, Logan, Utah. The farm has about 1 percent surface slope and is a well-drained Millville silt loam that occurs on an alluvial fan. It is high in potash and phosphorous and is alkaline, having a pH of 7.9 to 8.2.

Only mixtures gave significant percent forage protein results . Clipping, irrigation and fertilization treatments did not significantly affect the percent of forage protein but did affect the forage yield and thus the total protein production per acre. The total forage protein yield increases were n early lineal with the nitrogen treatment increases.

The yield of forage from the 35 day clipping frequency was greater than from the 28 day clipping frequency for all five mixtures. The mixtures containing alfalfa showed greater response to the harvest frequency in increased forage yield than the other mixtures.

All nitrogen applications gave forage yield increases. The first 50 pound increment gave the greatest and the second 50 pound increment gave the l east forage yield response.

The different irrigation intervals, with the same total seasonal water applied, resulted in no significant forage yield differences.

Ladino clover had the greatest root dry weight per acre with the 28 day harvests and 50 pounds of nitrogen. The alfalfa and grass root dry weights per acre were largest with the 35 day harvests, the first 50 pound increment of nitrogen application and the longest irrigation lnterval. A mixture of alfalfa and intermediate wheatgrass had the high alfalfa root dry weight and the low grass root dry weight yield per acre.

Ladino clover roots were high in both the percent and pounds of total available carbohydrates (TAG) per acre with the 20 day irrigation interval and with five harvests. Grass roots percent and total pounds of TAG per acre were high with five harvests. Alfalfa root TAG per acre was nearly double with four harvests over five harvests and showed the greatest response to the first 50 pounds of nitrogen and the 20 day irrigation interval.

Five harvests gave higher root to forage (R/F) ratios for all mixtures except the ladino clover-grass mixture.

Zero pounds of nitrogen gave the highest R/F ratio for the grass-only mixture. Fifty pounds of nitrogen gave the highest R/F ratios for the other four mixtures.

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