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Intercropping of corn and alfalfa

Berti, Lenssen, Wells, PhD student Swetabh Patel, Maciej Kazula, postdoc

 

The experiment was conducted in North Dakota, Minnesota, and Iowa, the results from 2018 are described separately for each state.  Data from all three states willbecombinedandanalyzed andpublishedin2019.

North Dakota

The experiment was conducted at three environments in Prosper and Forman, ND established in 2016 and Prosper established in 2017. The resultsacrossthethreeenvironments,indicatethatalfalfayield was greater for alfalfa established alone the first year compared with the other treatments. Alfalfa intercroppedintocornatestablishment,withorwithoutprohexadioneapplication,hadloweryieldthanalfalfaseeded alone, but 2.2 to 2.5 times greater yield than the spring-seeded alfalfa following corn (business-as-usual).

In the third year of production (alfalfa established at Forman or Prosper in 2016), alfalfa yield was similar for all four treatments.

 

Quick economics calculation with the results in North Dakotaindicatethis system has a positive outcome. In Year 1, corn yield decreases on average 30 bu/acre due to the competition alfalfa imposes. In Year 2, alfalfa yield increases in about 2.5 tons/acre compared with spring-seeded alfalfa. With corn at $3/bu and alfalfa at $100/ton. 30x3=$90/acre loss in Year 1 and $100 x 2.5= $250 gain in Year 2, with a balance of $160/acre. A publication in the economics of this system is in progress and will be published shortly.

 

Iowa

In Ames, all data wascollectedontime from a replicated trial of corn-alfalfa intercropping study. At each cutting of alfalfa biomass; plant height, growth stage and stem andplantcountdata wascollectedfrom1 m2 flagged area in each plot where alfalfa was present. Weeds were also counted and identified before every cutting. Totalfourcuttingswas obtained from thealfalfaenteringin to first or second production year (2016 and 2017 planted alfalfa) while only two cuttings were obtained from spring 2018 planted alfalfa. Alfalfa biomass samples were dried, grounded and sent to NDSU for protein and fiber analysis.

There was noeffectofprohexadioneonintercroppedalfalfaenteringintoeitherfirstor the second year of its full production. Solo alfalfa had significantly higher yield in the first production year than alfalfa treatments established under the corn canopy.

For the study started in 2016andenteringintothesecondyearof full alfalfa production, treatment 1 (alfalfa only) and treatment 5 (spring-seeded alfalfa) had higher total biomass production compared to intercropped alfalfa. However, for study started in 2017andenteringintothefirstproduction year of alfalfa, the intercropped alfalfa yield was atleastsixtimehigherthanthat of spring-seeded alfalfa. Results inyear2018 were similar to that of 2017 indicating that alfalfa intercropped with corn has greater productivity in the following year compared with spring seeded-alfalfa (T5) anduseofprohexadionedidnotprovide benefit in improving alfalfa production. Productivity, economic, and environmental benefitoftheinterseededcorn/alfalfa system provide powerful incentives for continuing development of this system for use in cold temperate regions.

A fifth site was established at the Southern Research and Outreach Center in Waseca, MN in 2016. The Waseca site experienced a state record-breaking 135 cm of precipitation in 2016. Much of this fell during rainfall events exceeding 7 cm in 24 h. Due to the wet season, the alfalfa stands at the Waseca site experienced multiple diseases that favor damp and humid conditions (crown rot, common leaf spot, and black stem). In 2017, we relocated the Waseca portion of this collaborative effort to Rosemount Research and Outreach Center located in Rosemount, MN. In 2017 corn grain yields were impacted by the alfalfa +prohexadione(PHD) treatments when compared to the check (Figure 17).  

Although corn grain yield differences were relatively small when compared with the check (Figure 18), alfalfa stand within the corn canopy did not differ between the alfalfainterseedingtreatments (Figure 19). Even though there were no differences between the two alfalfa treatments, alfalfa stands were less than optimal.

 

 

In 2018 at Rosemount, MN, alfalfa yields were lower than the alfalfa check treatment during the first cut. By the second harvest the alfalfa interseeding treatments did not differ from the check (Figure 20). The alfalfa did not recover enough during the second and the scheduled third cutting due to hot and dry conditions, so the third cut did not take place.

2016-2017

The experiment was established in Prosper, and Forman, ND, Ames, IA and Waseca, MN in 2016. In 2017, the experiment continued at all locations except Waseca. The experiment was repeated with new plots established at Prosper, ND, Rosemount, MN and Ames, IA, in 2017. Treatments included: T1, solo-corn; T2, corn +alfalfa intercropped; T3, corn +alfalfa intercropped + prohexadione(PHX) (a growth regulator); and T4, an alfalfa control. Corn plots were planted first with plot drill at 76 cm, and alfalfa was drilled over the corn plots with an 8-row plot seeder at 15-cm row spacing. Each experimental unit had either four rows of corn or four rows of corn and 16 rows of alfalfa seeded on top of the corn on the same date. The alfalfa and corn cultivars were glyphosate-resistantcultivar. The targeted corn plant density was 88,000 plants ha-1 and the seeding rate for alfalfa was 15 kg ha-1. Prohexadione calcium was applied to alfalfa at 20-cm in height at a rate of 0.5 kg a.i. ha-1 over the alfalfa, but under the corn canopy. Seedingdatesandprohexadione application dates are indicated in Table 17.

 

In the seeding year, alfalfa seasonal forage yield was significantly greater when alfalfa did not have to compete with corn during establishment in all environments except at Ames in 2017 (Table 18).  The solo-alfalfa in Ames in 2017 was mowed by mistake at the beginning of the season, so only one harvest was taken in 2017, hence the low yield. Alfalfa biomasses under the corn canopy were similar between treated and untreated, indicating PHX did not improve alfalfa biomass in the seeding year. Seasonal forage yield of alfalfa established in 2016 was significantly higher than the spring-seeded alfalfa at all locations.  Forage yield was three to four times higher than the spring-seeded alfalfa. The PHX application did not increase alfalfa forage yield at any locations.

 

Solo- alfalfa seeded in 2016 had significantlyhigheryield (2-5 Mg ha-1) in the first production year (2017) than alfalfa treatments established under the corn canopy. This indicates that the competition for light and perhaps nutrients in the seeding year does reduce alfalfa yield potential in the first production year.A future economic analysis should consider the loss in forage yield in the production year compared with solo-alfalfa established in the same yearasinterseeded alfalfa.Although, comparedwitha spring-seeded alfalfa this system seems promising, the potential yield loss in the production year might offset the gain.

 

Plantdensitiesatallenvironmentswaslowerthan expected (Table 19). However, forage yield in the first production year was within the average forage yield obtained at all locations.  The differences detected in alfalfa plant density among treatments varied across environments and were insufficient to explain the alfalfa forage yield differences observed in the first production year. In four out of ten environments, competition with corn reduced alfalfa plant density compared with solo- alfalfa. PHX application did not improve alfalfa stand survival (Table 19). In the seeding year,establishmentofalfalfa under the corn was poor in Rosemount 2017 for both treated and untreated alfalfa. In Waseca 2016, the alfalfa treated with PHX had much lower density, response very difficult to explain. As indicated before, the early-maturing corn grain hybrids chosen in our study probably let enough light through the canopy for alfalfa to survive without the aid of PHX. Corn silage grows typically taller which reduces available light within the canopy for alfalfa to grow.

 

The response of intercropping systems on corn grain yield or total biomass was not consistent across environments.  Corn grain and biomass yield wasnot affected by treatments at most locations with the exception of Forman and Prosper in 2016 and Rosemount in 2017 (Table 20). The latter only for biomass yield. Also, corn was significantly taller in treatments without interseededalfalfa in Forman in 2016.  This is an indication thanin years with below-normal rainfall in critical months for corn growth, alfalfa interseededmay compete for water and reduce both grain and biomass yield. The rainfall deficit observed in 2016 was 62 and 60% of normal, respectively, in June and August, in Prosper, and 55% of normal in June in Forman.  The deficit in June at both locations likely gave a head start to the interseededalfalfa. In June alfalfa, had enough light available to compete heavily for water with corn. Alfalfa probably depleted the available water from the first 20 cm of soil in June, limiting the amount of water available for corn. The biomass accumulated of alfalfa in intercropping at the end of the season fluctuated between 0.32 and 0.47 Mg ha-1which would only explain a small portion of the water used. However, alfalfa biomass earlier in the season was much greater, but plants at these two locations were defoliated after severe potato leafhopper damage.

 

Table 17.  Seeding dates and proxehadione (PHX) application dates at all locations and years.

Location

Corn seeding

Alfalfa seeding

Prohexadione

Spring alfalfa seeding

Forman

  3 May 2016

4 May 2016

17 June 2016

  2 May 2017

Prosper

  5 May 2016

5 May 2016

16 June 2016

  2 May 2017

Ames

17 May 2016

17 May 2016

24 June 2016

16 May 2017

Waseca

19 May 2016

19 May 2016

30 June 2016

-†

Prosper

12 May 2017

12 May 2017

26 June 2017

-

Ames

16 May 2017

16 May 2017

  5 July 2017

-

Rosemount

  5 May 2017

  5 May 2017

11 July 217

-

 † Waseca flooded in 2016, thus no alfalfa plants survived to evaluate in 2017, thus spring seeding was not conducted


 

Table 18. Alfalfa seasonal forage yield in each treatment at four locations in the seeding year and first production year.

 

Prosper

Forman

Rosemount

Ames

Treatment

2016

2017

2017-Yr1†

2016

2017

2017

2016

2017

2017-Yr1†

-----------------------------------------------------------Mg ha-1----------------------------------------------

Alfalfa seeded in spring

.

5.33

4.12

.

4.52

1.41

1.13

0.69

Alfalfa seeded in 2016

6.84

15.46

.

8.82

14.18

.

1.57

10.05

.

Alfalfa + corn

0.46

12.6

0.73

0.47

12.48

0.46

0.22

5.67

0.93

Alfalfa + corn + PHX‡

0.32

11.48

0.48

0.37

11.82

0.39

0.16

5.31

0.64

LSD (0.05)

1.69

0.9

0.51

1.27

2.2

0.55

0.34

2.26

NS

CV,%

38.6

5.2

16.5

22.7

13

42.8

30

22.5

52

†The experiment were repeated in Prosper and Ames in 2017 at the same location

‡PHX: prohexadione calcium, rate of 0.5 kg a.i. ha-1

 

Table 19. Plant density of alfalfa in each treatment at five locations in the seeding year (Year 1) and first production year (Year 2).

 

Prosper

Forman

Rosemount

Waseca

 Ames

Treatment

Year 1

Year 2

Year 1

Year 1

Year 2

Year 1

Year 1

Year 1

Year 2

Year 1

-------------------------------------------------------no. plants m-2-------------------------------------------------

Alfalfa seeded in 2017

.

44

42

.

.

94

52

.

36

25

Alfalfa seeded in 2016

48

45

.

49

42

.

.

74

57

.

Alfalfa + corn

44

60

53

34

40

18

52

25

33

30

Alfalfa + corn + PHX

35

63

67

28

40

18

16

23

31

28

LSD (0.05)

NS

NS

NS

10

NS

21

NS

15

13

NS

CV, %

20

16

37

16

15

24

123

21

22

44

PHX: prohexadione calcium, rate of 0.5 kg a.i. ha-1


 

 

Table 20. Corn grain and biomass yield dry matter in response to alfalfa interseeding treatments at six environments

 

Ames 2016

Ames 2017

Forman 2016

Prosper 2016

Prosper 2017

Rosemount 2017

Waseca 2016

Treatment

gr

bio

gr

bio

gr

bio

gr

bio

gr

bio

gr

bio

gr

bio

---------------------------------------------------------------Mg ha-1-------------------------------------------------------------------------

Check

14.9

34.0

12.7

33.4

14.9

33.5

14.9

25.3

10.9

32.7

12.2

23.9

14.1

.

Alfalfa + corn

13.2

26.8

15.2

29.9

12.5

24.4

11.1

18.1

11.1

26.5

9.8

21.0

12.2

.

Alfalfa + corn + PHX

12.8

29.5

14.1

30.7

13.2

25.3

12.5

21.3

11.4

26.2

9.7

20.2

11.8

.

LSD (0.05)

NS

NS

NS

NS

1.5

6.9

2

4.4

NS

NS

NS

2.6

NS

CV, %

10.8

13.4

21.3

19.8

6.8

14.8

9.3

12.2

11.8

13.7

11.4

6.1

9.3

PHX: prohexadione calcium, rate of 0.5 kg a.i. ha-1, gr=grain, bio=biomass


2017

The experiment was established in Prosper, and Forman, ND, and Waseca, MN in 2016. The design for this experiment was a randomized complete block (RCBD) with four replicates.  Treatments included: corn at 76-cm row spacing, corn +alfalfa intercropped, corn +alfalfa intercropped + prohexadione calcium(PHX), and an alfalfa control. Corn plots were planted first with plot drill at 76 cm, and alfalfa was drilled over the corn plots with an 8-row plot seeder at 15-cm row spacing. Each experimental unit had either 4 rows of corn or 4 rows of corn and 16 rows of alfalfa seeded on top of the corn on the same date. The alfalfa and corn cultivars were glyphosate-resistant cultivar. The targeted corn plant density was 88,000 plants ha-1 (35,628 plants per acre). and the seeding rate for alfalfa was 15 kg ha-1 (13.36 lbs. per acre). Prohexadione calcium was applied to alfalfa at 20-cm in height at a rate of 0.5 kg a.i. ha-1 over the alfalfa, but under the corn canopy.

 The results combined across three locations indicated that alfalfa decreased corn grain yield in both treatments with and without PHX.  Corn check grain yield was 224 bu/acre, significantly higher than corn with interseeded alfalfa.  Alfalfa with corn had 194 bu/acre a 13.4% yield reduction and corn with alfalfa and PHX had a yield of 188 bu/acre, a 16% reduction in yield.  No significant differences were observed in corn yield between alfalfa treatments.

Alfalfa biomass at harvest was greater for T1 (alfalfa alone). Treated or not treated alfalfa under the corn canopy had similar biomass yield.

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