Alfalfa,Medicago sativa L., in highly weathered, acid soils
SummaryRooting into acid subsoils would be a desirable trait for alfalfa which should result in better water extraction and yield. In this study, the rooting depth into acid subsoils and top yield of alfalfa plants selected for acid tolerance were investigated in a repacked profile with a limed, fertile topsoil, but unamended, acid subsoil. The effects of subsoil modification by CaCO3 and CaSO4·2H2O addition on alfalfa rooting, top growth, and water extraction were also studied.Plants from acid selections rooted deeper into acid subsoil when compared to control plants (selected under limed conditions). However, the reverse response was found in the CaSO4·2H2O treated subsoil. There were no differences among selections for total top yield for any subsoil treatment. Water extraction from the lower subsoil and top growth yield (data pooled by selections) were improved mainly in the subsoil treatment containing the highest addition of CaCO3.
Opposite Alluminum and Manganese Tolerances of Two Wheat Varieties1
Acid soil and solution culture studies showed that ‘Atlas 66’ wheat (Triticum aestivum L.) from North Carolina was more tolerant to excess Al but less tolerant to excess Mn than ‘Monon’ wheat from Indiana. In greenhouse pots of Al-toxic Bladen soil (pH 4.6 to 5.1) the top yields of Atlas 66 were significantly higher (5% level) than those of Monon; liming the soil to pH 5.8, however, equalized top yields of the two varieties. In Mn-toxic Zanesville soil (pH 4.7 to 5.2) the varietal yield difference was just the reverse. At pH 5.2 the tops of Monon plants had fewer leaf symptoms (rolling and chlorotic spots) and yielded significantly more than those of Atlas 66; at pH 5.9 or 6.9, however, the two varieties were not significantly different in top yield. In nutrient solutions containing between 4 and 32 ppm Mn at pH 4.6 the tops of Monon showed fewer leaf symptoms of Mn toxicity and yielded significantly more than those of Atlas 66, but with O or 2 ppm Mn added, the top yields of the two varieties were not significantly different. With Mn levels of 2 to 32 ppm, Monon root yields were significantly higher than those of Atlas 66, but with no Mn added the two root yields were not significantly different. At all Mn levels of 2 to 32 ppm in solution both tops and roots of Monon contained higher Mn concentrations than those of Atlas 66, but Monon plants showed less injury. For example, in Monon tops 2,561 ppm Mn was associated with a yield reduction of 12%. In Atlas 66 tops 1,250 ppm Mn (the highest concentration reached in Atlas 66) was accompanied by a yield reduction of 21%. In Monon roots 8,534 ppm Mn was associated with a root yield reduction of 20%, but 7,172 ppm Mn in Atlas 66 roots coincided with a 45% reduction in root yield. Tolerance to one acid soil factor in a given plant genotype does not necessarily mean tolerance to another.
Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
Abstract Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1–1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.