Evaluation of Quantitative and Qualitative of Medicago scutellata Affected by Sowing Date, Sowing Depth, and Seeding Rate

Given recent droughts, Medicago scutellata Var. Rabinson has taken an important position in crop rotation, especially in semi-arid regions. Therefore, agronomy management factors play an important role in improving its growth. Also, regarding its short growth period length, its quantitative and qualitative forage yield has been high, and it can be sown through dry-farming in regions with 300-500 mm of rainfall. On the other hand, given the importance of forage cultivation in agriculture and water shortage in Iran, we can try to cultivate fallow lands. The aim of this study was to evaluate the effect of different agronomic management methods on the quantitative and qualitative snail medic forage yield and to compare the relative contribution of components to increasing it under the climate of Arak.

In this study, two sowing dates (July 15 and 22, 2017) as main plot, two sowing depths (1-2 and 2-4 cm), and four seeding rates (2.5, 7.5, 12.5, and 17.5 kg ha-1 equal to 20, 50, 80, and 125 plants m-2) as subplots were investigated. The experiment conducted in split plot factorial based on randomized complete block design with three replications. It is noteworthy that due to seed hardness, the average number of germinated seeds was low. The measured traits in this study included forage dry weight, stem dry weight, pod dry weight, leaf dry weight, number of pods per m2, leaf area index (LAI), dry mater digestibility (DMD), crude protein (CP), crude fiber (CF), crude ash (CA), acidic detergent insoluble fiber (ADF) and neutral detergent soluble fiber (NDF) in the final stages of forage harvesting. Finally, using the statistical software SAS, we performed analysis of variance, comparison of means using Duncan’s multiple range test at 5% probability level and correlation analysis.

The results showed that the highest dry forage weight and dry stem weight (2884.13 and 1361.71 kg.ha-1, respectively) were observed in the treatment of seeding rate of 12.5 kg ha-1, at sowing depth 1cm and on the sowing date of July 21. Accordingly, the amount of dry forage obtained from the sowing date of July 21 and the sowing depth of 1 cm was 10.77 and 19.84% more than that of the sowing date of July 5 and the sowing depth of 2 cm, respectively. The portion of dry stem weight in the sowing date of July 21 and sowing depth of 1 cm was 53.96 and 55.24% of the dry forage weight, respectively. Furthermore, the portion of the pod and dry leaf weights from the dry forage for sowing date of July 21 were respectively reported as 34.13 and 11.91%, and for sowing depth of 1cm were, respectively, 33.56 and 11.18%. As the amount of seeding rate increased, the CF increased, and the percentage of CP decreased. By taking into account the absolute value of the slope value of the equations of these two traits, it was found that the effect of density on the CF is more than the effect of this treatment of CPP. According to the obtained results, the sowing date of July 21, the sowing depth of 1 cm, and the consumed seed of 12.5 kg ha-1 showed an appropriate quantitative and qualitative yield. Also, according to the results of the correlation test, it was determined that the dry forage produced had a positive correlation with the stem dry weight (0.99**), the pod dry weight (0.99**), the leaf dry weight (0.98), the number of pods per m2 (0.43*), the CA (0.71**), DMD (0.78) and NDF. On the other hand, a negative correlation was found with LAI (-0.66**) and ADF (-0.53**).

Regarding the absolute value of the slope in the equations pertaining to these two properties, it was found that the susceptibility of fiber percentage to density was higher than the susceptibility of crude protein percentage in this treatment. In deeper sowing, the obtained protein percentage was 1% lower, while the lowest fiber percentage occurred in shallow sowing. Generally, we can say that this crop has a high sensitivity to high densities. Based on the results, there were the relation between regression and correlation results.