Sterility in hybrid cattle. I. Distribution of constitutive heterochromatin and nucleolus organizer regions in somatic and meiotic chromosomes.

The distribution of constitutive heterochromatin and nucleolus organizer regions (NOR's) in somatic as well as in meiotic chromosomes of Bos taurus, Bos banteng, Bison bison, and their hybrids are analyzed. C-bands are present in the centromeric regions of every autosome. The X chromosome does not show a distinct C-band in the centromeric region, whereas the Y chromosome contains an appreciable amount of C-band material. In somatic metaphases, NOR's are present on the telomeric ends of five pairs of autosomes. During pachytene, five autosomal bivalents contain NOR's on their terminal ends. Meiotic preparations made from sterile bulls did not contain stages beyond the degenerating pachytene, which are C-banding, more frequently showed clustering of heterochromatin than did the pachytene stage in normal bulls.     

How much is soil nitrous oxide emission reduced with biochar application? An evaluation of meta-analyses

Nitrous oxide (N₂O) is the third important long-lived greenhouse gas next to carbon dioxide and methane and croplands are considered biogeochemical hotspots of soil N₂O emissions. To reduce soil N₂O and other greenhouse emissions, climate-smart agricultural practices including biochar application have been applied. Many studies have been conducted with biochar application but results from these studies are not conclusive. To address this issue, meta-analysis, a quantitative review that synthesizes results from multiple independent studies, has been widely used. The results from different meta-analyses also differ but are seldomly evaluated. In this study, we evaluated meta-analyses on the effects of biochar application on soil N₂O emissions. A grand mean response ratio (RR) was further proposed to estimate an overall effect and the impacts of experiment setting, properties of biochar and soil, and agricultural practices. We found 18 meta-analysis papers were published between 2014 and 2022. Sample size (publications or experiments) varied from less than 30 to more than 1000, with a mean sample size of 275. RR was calculated in all studies except one. While four meta-analyses did not find a significant effect of biochar application on soil N₂O emissions, all others reported reductions of soil N₂O emissions, but the magnitude ranged from −10.5% to −54.8%. Synthesizing all results from these meta-analyses, we found that biochar application overall significantly reduced the soil N₂O emissions by 38.8%. The impacts increased with experimental duration till one and half years and reduced after that. Biochar application rate and C:N ratio had large influence on the effects of biochar application on soil N₂O emissions. This study demonstrated that while meta-analysis provides a more comprehensive and better estimation, the inconsistence among these studies may need to be further evaluated. A grand mean RR based on meta-analyses could be more accurate and representative than single meta-analysis.