Proc. 56^th Southern Pasture and Forage Crop Improvement Conference, Springdale, AR April 21-22, 2001

Sub-tropical Grain Legume – A Potential Forage for Southern Plains

Srinivas C. Rao srao@grl.ars.usda.gov and William A. Phillips

USDA-ARS, Grazinglands Research Laboratory
El Reno, OK 73036

INTRODUCTION

Pigeon pea (Cajanus Cajan L.) is one of the major grain legume crops of the sub-tropics and ranks sixth in world wide dryland legume production (Nene and Sheils, 1990). It is now widely grown in the Indian subcontinent which accounts for almost 90 % of the world pigeon pea production. Pigeon peas are also grown in southeast Asia, Africa and the Americas.

Pigeon pea can survive well in poor soils and an outstanding root system enables it to tolerate drought. This crop has been used in a variety of ways. Dry seed are used as high protein grain for human consumption (Whiteman and Norton, 1985), forage as animal feed (Pathak, 1970; Wallis et al. 1986; Whiteman and Norton 1981; Whyte et al. 1953) and the plants as a green manure crop (Gooding, 1962).

Chemical composition of pigeon pea varies depending on maturity and on the proportion of various plant components such as leaf, stem, and pods. Akinola and Whiteman (1975) measured N content in plant parts at different growth stages and reported that four-week old leaves and stems contained 4.78 and 2.76 % N but declined to 3.64 and 1.76 % N at 16 weeks, respectively. As a standby forage, a good pigeon pea stand can supprt beef cattle from 1.2 to 3.7 head ha ^-1 , with an average daily gain (ADG) of 1 kg head ^-1 d ^-1 (Krauss, 1932). Test in Hawaii by Henke et al (1940) suggested that pigeon pea forage was superior to grass in supporting livestock performance and had higher nutritional value and stocking rate. Pigeon pea is a new crop to the Southern Great Plains. This study was undertaken to determine the seasonal forage production patterns and nutritive value of forage-type pigeon peas grown during the summer fallow period of a continuous winter wheat production system.

Materials and Methods:

Three pigeon pea cultivars [ ICP8151 (long duration), ICPX 91007 (medium duration) and PBNA (dwarf, long duration)] were obtained from International Crop Research Institute for Semi-Arid Tropics (ICRISAT), India. Plots were disked twice soon after winter wheat harvest in mid June and 60 kg phosphorus ha^-1 was broadcast applied before a second disking. Seeds were planted at the rate of 30 kg ha^-1 in rows spaced 60 cm apart. The experiment was conducted in three years, 1996-1998. The crop was grown under rainfed conditions. Plants were hand clipped at a height of 2.5 cm from three 0.5 m segments in a row beginning 60 d after planting, and continued at two to three- week intervals until the first week of October. Plants were dried in a forced-draft oven at 65 ⁰C for 60 h, separated into leaf and stem, then ground (1-mm screen) and stored. Plant samples were analyzed for N and digestibile dry matter concentration.

Results and Discussion:

The amount and distribution of precipitation during the study period varied among years. Total precipitation amounts in 1996 and 1997 were slightly greater (5 and 11 cm ) than the 25-y average (49.9 cm). Precipitation during the 1998 growing season was 70 % lower than the 25-y avarage. Mean temperature in 1997 was 2 ⁰C lower and in 1998 2 ⁰C warmer than the 25-y average mean temperature of 24.5 ⁰C, during the growing season.

Pigeon pea ecotypes differed significantly (P<0.05) in DM production only at the last sampling date, October 3 (Table 1). The ecotype ICP 91007 accumulated the greatest amount of dry matter (15.8 Mg ha^-1), follwed by ICP 8151 (12.5 Mg ha^-1) and PBNA (9.4 Mg ha^-1). Lower DM accumulation for ecotype PBNA was due to its dwarf, bushy stature. Its bushy stature and the overlapping of leaves may have reduced light interception.

Nitrogen concentration and in vitro DM digestibility of above-ground plant material declined as the season progressed . Quality parameters were significantly different (P<0.05) among pigeonpea ecotypes. Mean N content in PBNA was 28.6 g kg^-1 as compared to 23.3 and 23.0 g kg^-1 for ICP8151 and ICP910007, respectively (Table 2). Dry matter digestibility was 614 g kg^-1 for PBNA, followed by 576 and 572 g kg^-1 for ICP8151 and ICP910007, respectively. Higher DM yield for ecotypes ICP8151 and ICP910007 may have diluted the nutrients, particularly N, thereby reducing its concentration in the total biomass as compared to PBNA. The differences in N and DM digestibility values were not significant (P<0.10) for ICP8151 and ICPX910007.

Short duration pigeon pea cultivars produce seed in the Southern Great Plains. A study was conducted with twenty-four lambs to determine the DM and protein digestibility and nitrogen balance of diets containing alfalfa, cottonseed meal, or raw pigeon pea seed as the protein source. Dry matter digestibility was similar among the diets containing pigeon pea, cottonseed meal or alfalfa, but the protein digestibility for the pigeon pea diet was lower (P<0.05) than the diet containing alfalfa. We conclude that pigeon pea seed can be used as a protein source in the diets of lambs and that one unit of raw cracked pigeon pea seed can replace 0.6 units of corn and 0.4 units of cottonseed meal without lowering diet digestibility and N retention (Table 3).

REFERENCES

Akinola, J. O., and P. C. Whiteman. 1975. Agronomic studies on pigeon pea (Cajnus cajan L. Millsp). 1. Field re- sponses to sowing time. Aust. J. Agric. Res. 26:43- 79.

Gooding, H. J. 1962. The agronomic aspects of pigeon pea. Field Crop Abstracts 15:1-5.

Henke, L. A., S. H. Work, and A. W. Burt. 1940. Beef cattle feeding trails in Hawaii. Hawaii Agric. Exp. Sta. Bull 84, Hawaii, USA.

Krauss, F. G. 1932. The pigeon pea: Its improvement, culture and utilization in Hawaii. Hawaii Agric. Exp. Sta. Bull 84, Hawaii, USA.

Nene, Y. L., and V. K. Sheila. 1990. Pigeon pea: Geography and importance. Pp. 1-14. In: Nene, Hall and Sheila (Eds), The Pigeonpea. C. A. B. International, Wallingford, Oxon, U.K.

Pathak, G. N. 1970. Red gram: In. Pulse Crops of India. Pp.14-53. Indian Council of Agric. Res, New Delhi, India.

Wallis, E. S., D. G. Faris, R. Elliott, and D. E. Beth. 1986. Varietal improvement of pigeonpea for smallholder livestock production systems. Pp 365-377. In: Proceding of the Livestock Systems Res. Workshop, 7-11, July 1986. Khon Kaen, Thailand.

Whiteman, P. C., and B. W. Norton. 1981. Alternative uses of pigeonpeas. Pp 365-377. In: Proceedings of the Int. Workshop on pigeonpea. Vol-1 15-19 December, 1980. ICRISAT, India.

Whyte, R. O., G. Nelson-Leissner, and H. C. Trumble. 1953. Legumes in agriculture. P 367. FAO Agricultural Studies No 21. Food and Agricultural Organization of the United Nations, Rome.

 

 

Table 3.   DM digestibility and nitrogen balance in lambs fed diets containing either alfalfa pellets (ALF), cottonseed meal (CSM) or pigeonpea (PP) as the source of protein.
Items	Diet
	ALF	CSM	PP	SE**
DM digestibility, %	79.2 b*	79.5 b	79.2 b	1.1
N intake, g/d	17.3 ab	16.2 b	19.6 a	1.0
Fecal N, g/d	4.7 b	4.7 b	6.7 a	0.4
Urinary N, g/d	8.9	8.5	10.0	0.5
N retention ;
Grams /d	3.7	2.9	2.9	0.5
Percent of N intake,%	21.4	17.6	14.4	2.2
Percent of N absorbed,%	29.6	25.0	21.9	2.9
*Means in the same row with different letters are different, P< 0.05. **Standard errorTechnical Abstract: A primary goal of livestock production systems is to have access to high quality forages year-round, to reduce the costs of harvested or purchased feeds. The primary forage resources for grazing livestock in the Southern Great Plains are winter wheat and warm-season perennial grasses. However, a void in livestock nutrient supply exists with this system from late July through late November, when quality and quantity of summer perennial grasses are declining and before winter wheat is available for grazing. We evaluated three pigeon pea ecotypes as potential solutions to this problem. The average yield of pigeon pea forage ranged from 1120 kg ha-1 in July to 12600 kg ha-1 in thefirst week of October. Nitrogen concentration and dry matter digestibility of plants averaged over the growing season ranged from 2.3 to 2.8% and 57 to 61%, respectively. Pigeon pea seed is also a good source of protein for livestock. One unit of raw cracked pigeon pea seed can replace 0.6 units of corn and 0.4 units of cottonseed meal without lowering diet digestibility and N retention. These results suggest that pigeon pea has the potential to provide high quality forage and grain that could be used as primary or supplementary feed for grazing livestock at a time when other forages are less productive.