If agronomic characteristics could be used as criteria for judging quality of corn and sorghum cultivars for silage, the selection of genotypes best suited for silage would be facilitated. The objective of this study was to determine if agronomic characteristics of corn (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench, S. sudanense (Piper) Stapf, and their hybrid] cultivars are related to their silage quality. Over a period of 3 years, 49 silages, involving 11 corn cultivars and 14 sorghum cultivars, were produced and fed to sheep in conventional feeding trials. Eleven of the 14 sorghum cultivars were the sweet‐stem silage type. We measured fodder yield, height, %dry matter, and % plant parts [stems, ears or heads (EH), and leaves]. The quality measurements were acid detergent fiber (ADF); in vivo measurements, with sheep, of digestible dry matter (DDM); average daily gain (ADG); and dry matter intake/animal/day (DMI). The highest correlations were obtained between % stems or % EH and quality for both corn and sorghum silages. Percent leaves and plant height were in some cases highly correlated with quality measurements, but these relationships could be explained by high correlations of % leaves and plant height to % EH and stems. ADF concentration was lower in corn silage (29.0%) than in sorghum silage (34.9%). The low ADG of sheep fed sorghum silage (18.1 g compared to 64.5 g for corn silage) was primarily due to low DMI (649 g) and low DDM (55.6%) of the sorghum silage compared to the high DMI (777 g) and high DDM (63.8%) of corn silage. A regression analysis showed that nearly equal amounts of DDM intake above maintenance were needed for a unit of ADG from corn silage and from sorghum silage.

Herbicides are effective for use in establishing alfalfa (Medicago sativa L.) without the use of a companion crop. The objective of the study was to assess the economic feasibility of the herbicide method as compared to the companion crop method and to determine some of its advantages and disadvantages. Productivity of ‘Vernal’ alfalfa established with or without a companion crop was determined at four locations in Minnesota. Oats (Avena sativa L.), harvested for either hay or grain, was used as the companion crop. Four herbicide treatments (EPTC, EPTC + 2,4‐DB, trifluralin, and benefin) were used for weed control when the alfalfa was grown alone. The EPTC soil incorporated treatment plus a postemergence treatment of 2,4‐DB on the alfalfa at the 3 to 4 trifoliolate‐leaf stage was the most effective treatment for controlling weeds. With prices of $27.56/MT for alfalfa hay, $4.20/100 kg for oat grain, and $16.54/MT for oat straw, the net return (excluding costs common to all methods) favored alfalfa establishment with oats harvested for grain and straw. During the establishment year the oat hay companion crop yielded 5.17 metric tons (12% moisture)/ha, while alfalfa grown alone yielded 4.03 metric tons/ha. Oat grains averaged 2,205 kg/ha, and straw yields averaged 5.46 metric tons/ha. Stand counts of alfalfa in the fall of the seeding )year were generally higher for alfalfa grown without a companion crop, but this did not affect the following year's yield. With prices of $27.56/MT for alfalfa hay, $4.20/100 kg for oat grain, and $16.54/MT for oat straw, the net return (excluding costs common to all methods) favored alfalfa establishment with oats harvested for grain and straw.

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While many laboratory procedures have been proposed for estimating feeding quality of perennial grass and legume forages, none have been adequately tested for their potential in predicting quality of corn and sorghum silages. The objective of this phase of a comprehensive study was to assess the value of six biological procedures proposed for predicting forage digestibility of silages of corn (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench, S. sudanense (Piper) Stapf, and their hybrid). In vivo digestible dry matter (DDM) of 51 corn and sorghum silages (17 in each of 3 years) was determined using sheep in conventional feeding trials. A modified Tilley and Terry (1963) in vitro procedure (T‐T DDM), gave the highest correlations with in vivo DDM (r = 0.83 for corn silages and 0.91 for sorghum silages). A “direct acidification” in vitro rumen fermentation procedure resulted in in vitro DDM which was also highly correlated with in vivo DDM (r = 0.50 and 0.91 for corn and sorghum silages, respectively). Within the corn silages, the correlation between direct avidification DDM and in vivo DDM of 18 entries with high grain percentages was only 0.19, while that for seven entries with low grain percentages was 0.93. Apparently, the combination of large amounts of available carbohydrates in the high grain entries and the phosphate buffer led to erratic growth and digestive action by the rumen bacteria. A 6‐hour rumen fluid fermentation procedure gave DDM values which were 36 to 38% of the T‐T DDM values and were poorly correlated with in vivo DDM. A cellulase‐acid pepsin procedure gave DDM values for both corn and sorghum silages that were 56% of the T‐T DDM values; however, cellulase‐acid pepsin DDM was positively correlated with in vivo DDM of sorghum silages (r = 0.72) and negatively correlated with in vivo DDM of corn silages (r = −0.42). Two procedures that involved the neutral detergent extraction (Goering and Van Soest, 1970) and a 48‐hour rumen fluid fermentation gave in vitro DDM values which were highly correlated with in vivo DDM (r = 0.73 to 0.90). A multiple correlation analysis revealed that little improvement of the simple correlation between specific laboratory procedures and in vivo DDM was attained by combining procedures. We developed simple regression equations to predict in vivo DDM from T‐T DDM and direct acidification DDM for corn and sorghum silages.

The laboratory drying procedures of lyophilizing, or oven‐drying at 50, 65, 80 or 100 C were applied to samples of fodder and silage of corn and sorghum. The residual moisture via vacuum desiccation over P2O5 and in vitro dry matter digestibility (IVDMD) were determined. The IVDMD of both fodder and silage was highest when dried via lyophilization. Lowest IVDMD was obtained from silage oven‐dried at 100 C. Drying at 65 to 80 C (rapid drying) was found satisfactory for determination of IVDMD of fodder or silage. However, large losses of IVDMD were experienced in slow drying of fodder compared to fast drying. For biochemical determinations of silage oven‐drying would not be satisfactory. High positive correlations were obtained between IVDMD of fodder and silage. Therefore, the IVDMD of corn and sorghum fodder should be a good measure of the relative differences which one might obtain in silage. The loss of IVDMD due to the ensiling process was 11.8%.