Fertilization strategies for high‐yielding alfalfa (Medicago sativa L.) should take in account the increase in soil nutritional status that occurred during the last decades in areas with intensive agricultural use. A field study was conducted at the University of Padova, northeastern Italy, to determine the response of alfalfa yield and nutritive value to various combinations of P and K rates in a soil lacking nutrient deficiency. Alfalfa cultivar Delta was seeded in March 2005 on a silt loam soil having 38 mg kg–1 available P and 178 mg kg–1 exchangeable K. Nine treatments deriving from the combination of three P fertilization rates (0, 100, and 200 kg ha–1 P2O5) and three K rates (0, 300, and 600 kg ha–1 K2O) were compared in a randomized complete block design. Plots were harvested at bud stage during three growing seasons (2005–2007) and dry matter (DM) yield, forage nutritive value, P and K contents, canopy height, and stem density were measured at each harvest. Soil samples were collected at the end of the research period for determination of available P and exchangeable K. The results demonstrated that P application had no impact on yield and did not interact with K in determining productivity, while K had a positive effect on yield. However, the 300 kg ha–1 K2O rate appeared sufficient to maximize yield, without adverse effects on the forage nutritive value. Data from soil analyses showed that alfalfa has a high K uptake even when it is fertilized at high rates.
Alfalfa (Medicago sativa L.) is the most important hay crop used in the dairy industry of the Po Valley, Italy, characterized by a subtropical climate with hot, humid summers and cool winters. Information is lacking as to selecting fall dormancy (FD) varieties adapted to the region and their response to intense harvest regimes. A 3-yr study was conducted to investigate the effect of two harvest regimes based on phenological stage (early bud and early flower) and three FD categories on productivity, canopy height, and leaf to stem proportion. Cultivars with FD ratings of 7.5 (less nondormant), 8.5 (nondormant), and 10.5 (very nondormant) were seeded in April 2005 at the experimental farm of Padova University in Legnaro, Italy. The experimental design was a randomized complete block in a split-plot arrangement. Canopy height and dry matter (DM) yield were measured at each harvest. Subsamples were collected to determine leaf area index (LAI), stem silhouette area index (SAI), and leaf dry matter to stem dry matter ratios (LSR). Nondormant cultivars had higher DM yield (18.2 Mg ha−1) than less nondormant (17.1 Mg ha−1) and very nondormant cultivars (16.9 Mg ha−1). Harvesting at early bud decreased DM yield by 11% compared to early flower. The FD categories had no effect on LAI/SAI and LSR ratios, however harvesting at early bud increased both ratios by 12.0 to 12.5%. Producers in subtropical climates may obtain alfalfa hay with a high portion of leaves at a reasonable yield from the three tested FD categories by cutting alfalfa at early bud stage
The widespread use of warm-season turfgrasses in transition zones of Europe, such as northern Italy, has been hampered by the long dormancy periods. To encourage the conversion from cool-to warm-season grasses, research is needed to identify cultivars that exhibit early spring green-up. A 2-year study was conducted at the agricultural experimental farm of Padova University from Novem- Dry weight values of WSC and CP for each cultivar were regressed against days needed to reach 80 % green cover in spring (D80). 'Yukon' exhibited the highest rhizome dry weight and WSC content during the winter months and was the fastest to reach 80 % green cover. Conversely, 'Princess 77' was the slowest cultivar to green-up in both years. Regression analysis revealed a stronger relationship between D80 and WSC than between CP content and D80.
Alfalfa (Medicago sativa L.) annual yield is not strongly related to fall dormancy (FD) rating in regions with mild winters, but nutritive value might be, especially when accounting for harvest management. Th e objective of this study was to compare the forage quality of alfalfa having three FD ratings, all within the nondormant group, under the eff ect of two phenologically based harvest regimes in a humid subtropical climate. Cultivars with FD ratings of 7.5 (less nondormant), 8.5 (nondormant), and 10.5 (very nondormant) were seeded in April 2005 at the experimental farm of Padova University in Legnaro, northeastern Italy. Plots were harvested at early bud or early fl ower from 2005 to 2007 and were subsampled at each harvest for nutritive value analyses. Diff erences were observed between FD ratings for weighted annual average (weighted by yield) neutral detergent fi ber (NDF), acid detergent fi ber (ADF), acid detergent lignin (ADL), crude protein (CP), ash, and ether extract (EE). For example, less nondormant cultivars had higher CP (193 g kg -1 ) than nondormant cultivars (190 g kg -1 ), and very nondormant cultivars (187 g kg -1 ). Harvesting more frequently improved forage nutritive value regardless of the FD rating used. Alfalfa harvested at early fl ower had NDF concentrations 18 g kg -1 higher than when harvested at early bud. All the chemical components studied were better correlated to the height of canopy than to the leaf to stem ratio (LSR). Results suggest that forage nutritive value was more impacted by stage of maturity than by FD rating or LSR.
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