Objective:

To evaluate the performance of alfalfa varieties with differing P and K fertility in rainfed and irrigated environments.

Summary:

This experiment was carried out under three environments:  1) rainfed in Creston, 2) irrigated in Creston, and 3) rainfed in Havre.  Tables 1 and 2 specify management information for Creston and Havre sites, respectively. Five different phoshorus (P) and potassium (K) fertilization treatments were applied (Table 3) as the main plot factor. Six alfalfa cultivars of varying fall dormancy (FD) ratings were used as the sublot factor (Table 4). Our long-term goal is assessing the impact of P and K fertilization on alfalfa yield, quality, and persistence.

Soil K level at Havre was high, thus no supplemental K was applied in 2019.  Urea was added to all plots in an amount equal to that of the N present in the monoammonium phosphate used for P fertilizer.

There were no significant differences in yield between treatments at either site, but there were statistically significant differences in yield between varieties only under irrigated conditions (Figures 1 and 2). 

The results of the first cutting quality analysis showed significant differences in protein levels between treatments, but the differences were not consistent between sites.  The rainfed trial had significantly higher protein than the irrigated trial in Creston.

Table 1. Management information for Creston, MT

 Seeding date: 5/22/19 Field: R8  
Emergence: 5/29/19 Harvest dates: 8/5 (rainfed); 8/6 (irr)
Seed Treatment: Apron XL + pre-treat   10/7 (rainfed); 10/11 (irr)
Seeding rate: 30 plants/ft2    
Previous crop: Faba Soil type: Fine sandy loam
Herbicide: Huskie/Axial: 5/23 Tillage: Conventional
Insecticide: None Soil residual nutrient  
    (NO3-1, P, K lb/A): 22-15-19
Fungicide: None Inoculant: PreVail (Verdesian)
 

Table 2. Management information for Havre, MT

Seeding date: 5/15/2019 Field: H  
Emergence: 5/25/2019 Previous crop: Pea/barley forage mix
Seed Treatment: Apron XL + pre-treat Harvest date: 8/2/2019
Seeding rate: 30 plants/ft2 Julian date: 214
Previous crop: Pea/barley forage mix Soil type: Clay loam
Herbicide: None Tillage: No-till
Insecticide: None Soil residual nutrient: NO3-1, P, K (lb/A): 50-11-319
Fungicide: None Inoculant: PreVail (Verdesian)
 

 

Table 3. Nutrients applied in 2019

Figure 1. Description of the fertilizer treatments at the two study locations

 

Table 4. Alfalfa varieties used in the study

 Variety Fall Dormancy
  
Maxi-Graze 2
Rugged 3
Alphatron 4
Saltiva 5
Cisco II 6
Magna 7
 

 

 

Figure 2. A bar graph of the yields by variety under both irrigated and rainfed conditions

Figure 1. Total yields (2 cuttings) at Creston, MT. Yields grouped under the same line are not significantly different at P<0.05.

 

Figure 3. A bar graph of the yields grouped by variety at the Havre, MT site

Figure 2. Total yields (1 cutting) at Havre, MT. Yields grouped under the same line are not significantly different at P < 0.05.

 

Table 5. Percent protein, phosphorus (P), and potassium (K) of alfalfa forage in rainfed and irrigated environments at Creston, MT. The same letter assignment denotes non-significance at P= 0.05 level.

  P, K Protein at NWARC

 

Table 6. Forage crude protein content of the rainfed environments between the study sites under various phosphorus (P) and potassium (K) rates. The same letter assignment denotes nonsignificance at P = 0.05 level within locations.

protein content of rainfed alfalfa forage in creston and havre