1. ADAPTATION OF WARM SEASON ANNUAL LEGUMES FOR FORAGE IN SOUTHEASTERN NEW MEXICO By: Jim Armendariz in cooperation with: Dr. Calderon-Mendoza, A. Islas, M. F. Martinez- Perez, F.E. Contreras Govea, S. Angadi, M. Marsalis, L. Lauriault, and Dr.Sergio Soto- Navarro

2. Background Plants are surrounded by nitrogen (N) in our atmosphere. Every acre of the earth’s surface is covered by thousands of pounds of this essential nutrient, but because atmospheric, gaseous nitrogen is present as almost lifeless nitrogen (N2) molecules, this nitrogen isn’t directly available to the plants that need it to grow, develop, and reproduce. Despite nitrogen being one of the most abundant elements on earth, nitrogen deficiency is probably the most common nutritional problem affecting plants around the world.

3. Introduction Legumes have the natural characteristic of fixing nitrogen from the environment to the soil without any additional cost to the farmer. This natural process provides the right amount of nitrogen to the legume, and leaves a certain amount of nitrogen in the soil for the next crop.

4. Introduction (Cont’d) Because intensive farming of many cash crops such as cotton, corn for silage, and winter wheat, depletes the soils if nitrogen, an additional legume crop has to be rotated with these crops in order fix nitrogen back into the soil. Traditionally in Southeast New Mexico, alfalfa (Medicago sativa L.) is the only legume rotated with these nitrogen depleting crops.

5. Introduction (Cont’d) Because of the benefit of this legume, It is important to identify new potential legumes that can be used in rotation with non-legume crops in addition to alfalfa.

6. Introduction (Cont’d) Because annual legumes such as Lablab-1 (Rio verde), Lablab-2 (Rongai), Cowpea-1 (Iron and Clay), Cowpea-2 (Catjang), and Trailing wildbean can be a good source of forage, and release some nitrogen into the soil for the next crop, these legumes could be a potential alternative crop for rotational grazing in addition to alfalfa in New Mexico.

7. Purpose The objectives of this study were to asses the adaptation of six annual legumes to Southeast New Mexico, and to determine forage yield potential, and forage nutritive value.

8. Materials and Methods This study was conducted at the NMSU- Agricultural Science Center- Artesia. Six annual legumes were planted on June 11, 2008. The experimental design was a complete randomized block design with 4 replicates Each legume was planted in a 1.2 x 4.5m plot (4 rows/plot) with 0.3m separation between rows. Each experimental unit had 1.5m of separation from one another. The legume seeds were inoculated with a specific Rhizobium strain by the seed company to help the legume fix nitrogen from the air into the soil in a shorter period of time. These legumes were grown in a Reagan Clay Loam soil.

9. Materials and Methods (Cont’d) Each plot was fertilized with 220Kg P₂O₅/ha, and 180 kg based on recommendations for alfalfa. Nitrogen was not applied on any plot. The seeds were irrigated 3 times before being harvested. They were harvested 1 time on September 4, 2008 (82 days after planting when plot canopy in Lablab beans was greater than 75%). All plots were hand clipped at a stubble height of 4 cm. A 150g subsample was taken from each plot, and oven dried at 60°C for 48 hours to prepare for laboratory analysis

10. Materials and Methods (Cont’d) The samples were ground in a Wiley mill to pass through a 2.0mm screen, and analyzed by near-infrared spectroscopy (University of Wisconsin, soils and forage analysis laboratory, Marshfield, WI) for CP, NDF, and ADF. Net energy for lactation was calculated using the Milk2000 spreadsheet (Schwab et al., 2001). Also, samples were incubated in 40ml of liquor that was in a 5:1 McDougall’s solution to rumen fluid, which is basically artificial sheep Saliva. The data was analyzed in a completely randomized design using the GLM procedures of SAS (SAS Inst. Inc., Cary, NC) with plot as the experimental unit. If the legumes were significant (P<0.05), means were separated using Fisher’s projected LSD with significance declared at P<0.05.

11. Results and Discussion After conducting this study we determined that Smoothe- wildbean did not germinate on any of the 4 plots Trailing-wildbean had very low germination. It is possible that the soil characteristics, or some other environmental factor was not appropriate for good establishment of these two native legumes, resulting in poor germination of these plants. On the other hand, Lablab-1, Lablab-2, and Cowpea-1 were the Legumes with greater (P<0.05) DM yield. Lablab-1 and Lablab-2 produced similar yield, but an average of 0.5 ton/ha more (P<0.05) than Cowpea-1 and 2.0 ton/ha P(<0.05) more than Cowpea-2 and Trailing- wildbean.

12. Results and Discussion (Cont’d) The DM yield of Lablab and Cowpea was similar to that reported by Fribourg, et al. (1984), and lower than those yields reported by Muir (2002), and Muir et al. (2008). Considering that the seeds were planted in June and only harvested one time, this DM yield can be considered acceptable for this region. Muir et al. (2008) reported DM yields from 3.2 to 5.4 ton/ha in Lablab and Cowpea respectively in 5 cuts in Texas. Therefore in Southeast New Mexico greater DM yield could be expected if planted earlier and harvested 2 or 3 times.

13. Results and Discussion (Cont’d) As far as Nutritive value, all five legumes had good quality characteristics. CP concentration ranged from 18 to 22%. NDF concentration ranged from 26 to 34%. ADF concentration ranged from 23 to 28%. Net energy for lactation (NEL) ranged from 1.52 to 1.66 Mcal/kg. Similar CP, NDF, and ADF concentrations were reported by Muir (2002) and Muir, et al. (2008) in Lablab and Cowpea.

14. Results and Discussion (Cont’d) In vitro DM digestibility was lower for Trailing- wildbean (38.2 ± 1.35%) than the other legumes which ranged from 45.2 to 48.6 (±1.35) %. In vitro DM digestibility values were 47.5, 45.2, 47.5, 48.6, and 38.2 ± 1.35% for Lablab- 1, lablab-2, Cowpea-1, Cowpea-2, and Trailing- wildbean respectively.

15. Implications It was evident that warm season annual legumes can grow in Southeastern New Mexico. More research needs to be conducted to more clearly identify the time period where these warm-season annual legumes can fit the forage production system or crop rotation system in New Mexico.

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