No abstract

Protein degradability in forage legumes is of global importance because utilization efficiency of forage has economic and environmental consequences. However, there are no published studies on the effect of legume stand structure on differences in crude protein (CP) fractions. The main objective of the present research was therefore to investigate differences in CP fractions in leaves and stems of lucerne (Medicago sativa L.) during the growing season. Stand traits were measured over 2 years, and forage was sampled at the early bud and early flower stages in the first, second and third cuts. Stems had significantly higher concentrations (in g kg−1 CP) of non‐protein (fraction A: 430 g kg−1 CP) and indigestible nitrogen (fraction C: 92 g kg−1 CP) than leaves and had lower relative content of true protein (fraction B: 478 g kg−1 CP). In the total forage (stems and leaves combined), about 80% of the variation in CP fractions was explained by year, cut and maturity. Year was the most important factor, particularly for the B fractions. Cut was the second‐most important factor; its main effect was that the relative abundance of fraction A declined from 394 g kg−1 CP in the first cut to 293 in g kg−1 CP the third cut. Maturity increased the amounts of indigestible fraction C and protein fractions B1 and B3. This was associated with the leaf weight ratio, which had an inverse relationship with maximal stem length and dry matter yield. Variation partitioning showed that 75% of CP fraction variability associated with cut, maturity and year could be explained by the evaluated stand traits. This research has highlighted the need to consider plant morphological traits when legume CP fractions are evaluated.

The root system of plants is generally regarded as a factor, which is in relation to important agronomic and ecological characteristics. The aim of this study was to investigate the effect of high initial stand density on the reduction in development of lucerne root morphology traits and how long-term this effect would be. In spring 2003, a field experiment with six lucerne entries in randomized blocks was established. Broadcast sowing was used and the seeding rate was 5000 germinated seeds per m 2 . In 2003-2009, the plants were sampled in each plot in autumn; the average depth of sampling was 0.2 m. The stand density reached an average value of 860 plants per m 2 in the autumn of the seeding year and this strongly reduced the root weight, tap-root diameter, position and number of lateral roots. The subsequent decrease of stand density to 57 plants/m 2 in 2009 was not linear but it was extremely quick from the 1 st to 2 nd year and, by contrast, it was extremely slow in the last three years. It indicates that older plants with larger tap-root diameter probably have a higher persistency. All evaluated root traits were developed slowly, nevertheless, they reached common values during a seven year period. The intensity of the relation of stand density to root weight or tap-root diameter increased over time whilst it decreased to the ratio of root-branched plants. Results suggest that an assessment of density in samples should be recommended for the varieties evaluation in case of irregularly-spaced plants because the differences in root morphology among varieties could be caused by the differences in density among the varieties. It is possible to conclude that lucerne stands under higher initial density provided a strongly reduced speed of root development with an impact on important agronomic traits connected with root morphology.

ABSTRACT:The goal of this study was to compare the growing degree-days (GDD) and predictive equations for alfalfa quality (PEAQ) for the prediction of lucerne quality and to test their accuracy and suitability in the first cut period in Central Bohemia. Several additional stand parameters were verified in order to increase the accuracy of the quality estimate under these environmental conditions. In 2004-2007, the measurement and sampling were repeatedly realized from the late vegetative to the early bloom stage in six replications. For the GDD model across the years, the obtained R 2 for NDF, ADF and CP were 0.40, 0.57 and 0.65, respectively. It seems that the forage quality response to accumulated GDD was related to the stand development and it could be the reason for low R 2 across all the years. For the PEAQ model, R 2 were 0.62, 0.92, and 0.85, respectively. Similarly like in the GDD model, the effect of stand development across the years on changes in the slopes of equations was observed. The accuracy of the model combination was not higher in comparison with the PEAQ model. The count of stems per plant, density of stems per m 2 , dry matter yield and average stem weight improved the NDF content prediction within a four-year period. In these models, variables which represent the stand development should be taken into account.

The reserve root nutrients influence the overwintering, regrowth, yield, and persistence of alfalfa plants. The total amount of the root reserves is considered more important than their concentration. One of the factors which can affect the reserve content can be the soil compaction. The aim of this study is to clarify the effect of the soil compaction on the reserve root nutrients in relation to the stand density and the amount of the root biomass. In this experiment, the stand density ranged from 28 to 112 plants per m². The average soil bulk density in the uncompacted and compacted variants was found to be 1.38 and 1.52 g/cm³, respectively. In spring and autumn periods, the root samples were taken from an area of 0.25 m² (the depth 150 mm) in four replications. The number of plants, the root weight, and the concentrations of starch, saccharose, fructose, and crude protein were assessed in each plot. The total amount of the root reserves was calculated from the determined concentrations and the weights of roots of each sample. A higher soil compaction reduced significantly the stand density, root weight, total amount of all nutrients as well as the starch and crude protein concentrations. The concentration of the soluble non-structural saccharides was identical to or increased over that in the compacted variant. The negative significant effect of a higher soil compaction on the root weight and, consequently, on the total amount of all reserve root nutrients was explained by the changes in the stand density. When the root weight effect was excluded, the compacted variant provided a significantly lower density and crude protein amount and concentration. The significant effect of density on the reserve nutrients was explained by changes in the root weight.