How Does Sowing Rate Affect Plant and Stem Density, Forage Yield, and Nutritive Value in Glyphosate-Tolerant Alfalfa?

Abstract

The recommended sowing rate of alfalfa (Medicago sativa L.) is about 10 kg pure live seed ha −1 , but it is debated if increasing the sowing rate enhances forage yield and quality in the sowing year. This study was conducted to: (i) determine the optimal sowing rate to maximize forage yield; and (ii) determine the relationship between plant and stem density with forage yield and nutritive value. Experiments were conducted at three sites in North Dakota between 2013 and 2016. Six sowing rates [1,5,10,15,20, and 25 kg ha −1 pure live seed (PLS)] were evaluated. Results indicated that total forage yield in the sowing year was lower only with the lowest sowing rate. Maximum total forage yield in the sowing, first, second, and third production years was obtained with 73, 52, 37, and 36 plants m −2 and 575, 495, 435, and 427 stems m −2 , respectively. In the sowing and first production year, both plant and stem density predicted forage yield similarly. In older stands, stem density predicted forage yield slightly better. Forage nutritive value was similar among sowing rates indicating an increase in sowing rate does not enhance forage nutritive value. In conclusion, increasing the sowing rate above the recommended rate (10 kg PLS ha −1 ) does not increase forage yield or quality. establishment with sowing rates above 17 kg ha −1 [5]. Volenec et al. [7] reported, when plant density is increased up to 172 plants m −2 , alfalfa yield per area was increased, but yield per plant decreased. Alfalfa stem diameter [8] and shoot weight [9] reduction has been associated with increased sowing rates. However, protein content does not increase with higher sowing rates [3]. In studies in the USA, during the first production year of alfalfa, optimum stand density to provide maximum yield varied from 140 to 260 plants m −2 [10]. Most studies have reported that increased sowing rates had limited effects on forage yield long term [2,6]. However, Glaspie et al. [11] reported conflicting results in which a sowing rate of 18 kg ha −1 [4], had the highest alfalfa yield both in the sowing year and in the first production year, compared with 10 kg ha −1 rate.One reason for the observed variability between forage yield and sowing rate is the difference in plant components and their ability to compensate stand loss over time [2]. In the northern Great Plains, alfalfa stand persistence and forage yield can be reduced due to winter-kill and winter-injury. In 2013, over 90% of alfalfa growers in Minnesota and Wisconsin reported winter-kill and winter-injury [12]. Most winter-kill happens when several weather factors such as above normal rainfall, lack of snow cover, and temperatures below −15 • C are combined [13]. Berti et al. [14] also reported a significant increase in the number of dead alfalfa plants in the spring following a fall harvest in the previous year, due to winter-kill. Plant density on average declined from 100 to 25 plants m −2 in four years, while the stem density decreased in the first two years, but it was stable at about 350...

Harvest interval effects on the persistence and productivity of alfalfa grown as a monoculture or in mixtures in the southeastern United States

“…According to Berti, Nudell, and Meyer (2012), as the stands gets older, stem density decreases regardless of the management adopted, which also explains the decrease FA in 2018. Similar results were reported by Berti and Samarappulli (2018), as stands aged, the plant and stem density decreased.…”

Alfalfa Established Successfully in Intercropping with Corn in the Midwest US

“…Plant density in North Dakota and Minnesota environments was lower than expected for a seeding year stand and spring of the year after planting [16,39], however it is not unusual to have extensive winter-kill and plant density reduction during the first winter [38]. Our plant count approach could have underestimated stand density relative to previous research where crowns were dug out.…”

“…In our study, based on PAR readings, alfalfa growing under a corn canopy received less than 20% of the incident radiation once the corn canopy closed, at about mid-July. Similarly, other researchers have reported corn canopy intercepts 80% to 90% of PAR [35,36]. In addition, alfalfa cultivars have different tolerance to shade [16].…”

Intercropping Alfalfa into Silage Maize Can Be More Profitable Than Maize Silage Followed by Spring-Seeded Alfalfa

“…In 2014, the alfalfa plant density was lower at the 61-cm row spacing for the PHX-treated alfalfa compared with the non-treated alfalfa, but similar in both treatments at 76-cm row spacing (Table 6). Intercropped alfalfa stands had a least 113 plants m −2 in the fall of 2014, which is within the range of 80-130 plants m −2 considered as adequate stand for the seeding year [11,33,34]. Grabber [11] reported just the opposite as the PHX treatment increased stand survival compared with the non-treated check.…”