Fall Harvest of Alfalfa: Impact on Stand Density, Forage Yield, and Forage Quality 2009-2010 Report Marisol Berti, Dwain Meyer, and Robert Nudell Dep. of Plant Sciences, North Dakota State University, Fargo, ND Introduction Fall harvest of alfalfa has been questioned in the past by producers in the northern tier of US states. Many producers will not take a fall harvest because they are afraid the fall harvest will increase winter-kill, especially on new stands. Previous work at Fargo suggested that alfalfa could be harvested in the fall when ready, defined as when alfalfa regrowth structures are about 2 to 3 inches in height from the bottom of the canopy. Objectives 1. Evaluate stand density of alfalfa harvested in the fall. 2. Determine forage yield of alfalfa in the year following fall harvest. 3. Determine forage quality of alfalfa during the first harvest to evaluate residue carryover Procedures Two experiments were conducted to meet the objectives. Experiment 1 was conducted in a four-year old alfalfa stand (variety unknown) in a farmer s field in Portland, ND. Four strips of 25 feet wide and 150 feet long were harvested in 2007 according to one of the following two treatments: a 3-cut system with the third cut in the fall, or only a 2-cut system with no harvest in the fall. In 9 May 2008, a 1-m 2 sample of whole plants was taken to determine total plant weight, aboveground (crown + overwintering residue), root weight, and number of plants alive and dead. Three harvests were taken in 2008. Forage yield and quality were evaluated. Experiment 2 was seeded 30 March 2007 in Fargo, ND, to beat the injunction placed on Roundup Ready alfalfa. The cultivar seeded was DKA34-17RR at 13 lb/acre with a double-discopener drill. Plots were 5 feet wide by 40 feet long. The experiment wase designed as randomized complete block with five replicates. 1
The experiment had two treatments: a 3-cut system with no fall harvest and a 4-cut system with a fall harvest when ready. In the seeding year only two harvests were taken, one at 30% bloom and the second one in the fall when ready. In the first, and second year of production the 3-cut system was harvested at 26 inches, late bud, and 30% bloom and the 4-cut system had an additional harvest in the fall when ready. Forage yield was harvested with a Carter Flail harvester. Forage yield is reported for 2007, 2008, and 2009. The fourth harvest was taken after the killing frost on 19 Oct. 2009 when the regrowth structure just reached the 2 to 3 inches ( when ready ). In the spring of 2009, crown and root samples were taken from one row of 5 feet in length and 6 inches wide. Number of total plants and dead plants, and the fresh weight of crowns and roots were recorded. Results Stand survival In Experiment 1, stand survivability in the third year of production in a farmer s field in Portland, ND, there were no significant differences between no fall and fall harvest for crown and root weights, and number of plants/m 2 (Table 1). Table 1. Crown and above-ground shoots and root fresh weight and plant density for alfalfa in the spring of 2008 following a 2- or 3-cut systems in the fall at Portland, ND, Experiment 1. Whole plant weight Root weight Crown/stem weight No. plants Harvest treatment L S D T L S T L S T L S D T alive -----------------------------------------g/m 2 ----------------------------------------- -------------plants/m 2 ------- No fall harvest 783 113 11 907 223 42 265 438 54 492 52 30 4 86 Fall harvest 640 147 16 802 224 66 290 364 66 430 41 35 7 82 LSD NS NS NS NS NS NS NS NS NS NS NS NS NS NS CV,% 14.4 32.9 70.9 9.8 21.4 50.4 20.1 20.7 37.6 18.9 22.7 43.4 45.5 28.8 Weight is indicated for large, small, and dead whole plants, crown/stems, and roots. L=Large, S=Small, D=Dead, T= Total. Large plants were those with roots larger than 2-cm in diameter. In Experiment 2, plant and root sampling in the spring of 2009 indicated that crown fresh weight, crown total yield, and plant density was significantly greater for the 3-cut system (Table 2). Stands were reduced from 7.5 plants/m 2 to 6.0 plants/m 2 and the number of dead plants was higher in the 4-cut system. Root weight and total root yield was not affected. The increased 2
above-ground crown weight in the 3-cut system was due in part to the residue left in the crown from last fall. The root weight did not differ between both treatments indicating root reserves were not changed. Winter-kill was greater during the 2008-2009 winter than observed any other year in the past 30 years. We delayed the first harvest in 2009 to allow plants to recover from winter injury that had slowed plant growth (Fig. 1); however, surviving stand s forage yield was not significantly different among treatments. Table 2. Crown and above ground shoots and root fresh weight and plant density for alfalfa DKA34-17 RR in the spring of 2009 following a 3- or 4-cut systems in the fall at Fargo, ND, Experiment 2. Harvest treatment Individual crown weight Individual root weight Plant density Dead plants Total crown weight Total root weight --------------g------------------ -----Plants/m 2 ----- ----------lbs/acre-------- No fall harvest 7.5 5.4 139 36 9081 6176 Fall harvest 5.6 5.1 111 19 5278 5067 LSD (0.05) * NS * * * NS CV, % 24.0 20.7 18.8 54.2 27.2 21.3 Seeding date: 3-30-2007. Crown and roots sampling date 4-22-09. Forage yield In Experiment 1, in Portland, ND, fall harvest tended to decrease the first harvest yield; however the second and third harvest yields were unaffected. Some of the forage yield differences in the first harvest was associated with picking up overwintering residue; however, the exact amount was not determined. The additional forage yield from the fall harvest more than offsets the slight yield loss. 3
Table 3. Forage yield of alfalfa in 2008 from treatments harvested or not harvested in the fall in 2007, in Portland, ND. Harvest dates Harvest treatment 6-19 7-30 9-9 Total ------------------------------------tons/acre ------------------------------------ No fall harvest 2.96 1.75 1.18 5.9 Fall harvest 2.28 1.79 1.08 5.2 LSD (0.05) NS NS NS NS CV,% 6.7 6.4 14.1 4.2 Results in Experiment 2 indicates that a 4-cut system, including a fall harvest, had significantly greater total forage yield in the first, second, and third years of production (Table 4). Forage yield in the seeding year was 2.09 and 1.45 tons/acre in Cuts 1 and 2, respectively, and 1.85 tons/acre with the fall harvest for a total of 5.39 tons/acre. Forage yield was 1.8 tons/acre greater for the fall-harvested than the no-fall harvested treatment in 2008. Likewise, forage yield was slightly higher, 070 tons/acre from the fall-harvested treatment in 2009. Table 4. Forage yield of DKA34-17RR alfalfa harvested or not harvested in the fall at Fargo, ND, in 2008 and 2009, Experiment 2. Year/Harvest dates 2008 Harvest treatment 6-16 7-15 8-14 10-9 Total ------------------------------tons dry matter/acre---------------------------------- No fall harvest 2.40 2.64 1.52-6.57 Fall harvest 2.41 2.36 1.64 1.95 8.37 LSD (0.05) NS 0.29 NS - 0.48 CV,% 8.8 6.0 11.6-2.7 2009 6-12 7-13 8-14 10-19 Total No fall harvest 3.33 1.98 1.50-6.81 Fall harvest 3.04 1.94 1.38 1.13 7.51 LSD (0.05) NS NS NS - NS CV,% 15.4 7.2 13.8-10.9 Seeding date: 3-30-2007. 4
Forage quality In Experiment 1, Portland, ND, the first harvest in 2008 following fall and no fall harvest treatment did not have any differences in quality (Table 5). The only difference in quality for this experiment was observed in the third harvest for IVDMD which was higher for the 3-cut system. In Experiment 2, in 2009, there were no significant differences in quality between fall and no fall harvest treatments. The average quality of the first cut was much lower than the second and third cut. As indicated before, in 2009 winter injury delayed plant growth obligating harvest to a later maturity hence the RFV of the first cut was the lowest of all harvests (Table 6). The quality of the 3-cut system in the first harvest was slightly lower than the 4-cut system and this could be due to an excess of overwintering stems from the last season in the 3-cut system. If plants received winter injury to some extent, it is necessary to delay the first harvest in the spring. This is an important concept on the fall harvest management system. In general, forage quality was higher for the third and fourth cuts, compared to the first and second cuts, in the first and second year of production as expected, considering the maturity differences of the treatments. There were few differences in forage quality overall among treatments. 5
Table 5. Alfalfa forage quality in 2008 from treatments harvested or not harvested in the fall in 2007, in Portland, ND. Harvest treatment CP ADF NDF ADL IVDMD HEMI RFV ----------------------------% of dry matter--------------------------- Cut 1 No fall harvest 19.6 44.8 33.9 7.5 69.7 10.9 148 Fall harvest 22.2 40.4 31.3 6.7 66.9 9.1 130 Cut 2 No fall harvest 22.1 32.8 41.4 7.1 68.5 8.6 142 Fall harvest 21.6 31.6 39.7 6.9 66.9 8.1 150 Cut 3 No fall harvest 23.2 24.4 32.5 5.2 73.7 8.1 200 Fall harvest 24.2 23.6 31.1 5.1 75.6 7.5 210 LSD (0.05) NS NS NS NS * NS NS CP = crude protein; ADF = acid detergent fiber; NDF = neutral detergent fiber; ADL = acid detergent lignin; IVDMD = in vitro dry matter digestibility; HEMI = hemicellulose (NDF-ADF); RFV = relative feed value. 6
Table 6. Alfalfa forage quality of DKA34-17RR harvested or not harvested in the fall at Fargo, ND, in 2009, Experiment 2. Harvest treatment CP ADF NDF NDFD IVDMD HEMI RFV ----------------------------% of dry matter--------------------------- Cut 1 No fall harvest 17.1 33.9 43.9 62.8 60.8 10.0 133 Fall harvest 18.9 29.0 37.2 70.9 67.1 8.2 166 LSD (0.05) NS 1.9 1.9 4.6 NS NS 7 Cut 2 No fall harvest 20.6 29.1 35.7 73.1 69.8 6.6 174 Fall harvest 21.2 28.3 35.2 74.4 70.1 6.9 178 Cut 3 No fall harvest 24.5 23.5 30.3 77.9 73.6 6.8 218 Fall harvest 24.3 23.2 28.9 77.1 73.6 5.7 228 Cut 4 Fall harvested 23.0 21.3 27.7 80.4 74.8 6.4 244 CP = crude protein; ADF = acid detergent fiber; NDF = neutral detergent fiber; NDFD = neutral detergent fiber digestibility; IVDMD = in vitro dry matter digestibility; HEMI = hemicellulose (NDF-ADF); RFV = relative feed value. 7