A total of 913 Piceaabies (L.) Karst. clones was tested for height at ages 1 and 5 in two series on six and three locations, respectively, in Sweden. The genotype × environment interaction was studied for three levels of genetic control, i.e., seedling checklot, clone mixture, and clone. Stability of all three was estimated using regression coefficients. The alternative method, genetic correlation between locations, was also used to measure stability. Height differences among seedling checklots and among clones were substantial at age 5, while the variation among clone mixtures was not significant. Genotype × environment interaction was found to be significant for clones and accounted for an average of 2.1% of the total variance at age 5. No significant interaction was found between mixtures and locations. The genotype × environment interaction for seedling checklots was not significant and accounted for 0.5% of the total variation at age 5. The stability of seedling checklots at age 5 was high. For the clone mixtures, stability was found to be about average. Individual clones showed wide variation in stability. There was an apparent negative relationship between clone performance and stability. Genetic correlations indicated close agreement between locations in the ranking of clones for height growth.

The development and testing of a new silage additive consisting of sodium nitrite and hexamine (hexamethylenetetramine) are described. The investigation was conducted over 8 years and consisted of 15 separate experiments with small steel cylinders and 13 with plastic sacks. The former were carried out with freshly cut blue lucerne and a storage temperature of 25°C. When a mixture of sodium nitrite and hexamine was applied at the rate of 0-4% of fresh herbage weight, the quality of the resulting silage was superior to that made with commercial additives marketed in Sweden and the losses were considerably reduced.

Seventy-five clones of Norway spruce (Piceaabies (L.) Karst.) were tested for height, diameter, and volume at two locations in southern Sweden. Total height was measured at seven ages from age 1 to 10 years, whereas diameter at breast height was measured and volume index calculated only at age 10. Clone effects were consistently significant for all traits, whereas clone × location interaction effects only showed significance for diameter at breast height at age 10, volume index, and height at age 3. Location effects for height were small and error effects large, up to age 6. Between ages 7 and 10, location effects increased considerably, while error effects decreased correspondingly. Clone-mean heritability for height remained stable from years 3 to 10, but was slightly higher at age 1. Genetic correlations between traits were generally large, which made efficient selection for height possible as early as age 4. The correlated response in volume index at age 10, when selecting for height at age 4 or later, was exceptionally good, and it provided gain estimates in volume that were as large as or larger than estimates from direct selection for volume index at age 10.

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