M.S. Taylor
FA O Agronomist, Pasture and Forage Crops, Institute of Agricultural Research, Addis Ababa, Ethiopia
4.2 Comparison of rhyzobial strains
Leucaena leucocephala is native to Central America where it is sometimes found in areas with a prolonged dry season of up to eight and a half months (National Academy of Sciences, 1977). It is, however, generally cultivated and performs vigorously in tropical and sub-tropical lowland areas with a sub humid or humid climate. This leguminous tree/shrub is gaining wide acceptance for use as a high quality fodder or browse.
Growth rate is greatly influenced by temperature and thus by altitude and latitude. The plant thrives only below 500 m elevation in Hawaii (National Academy of Sciences, 1977), at 1600 m in Indonesia and up to 1800 m in Colombia (Skerman, 1977). Western Ethiopia has extensive areas of land between 1300 and 1800 m elevation receiving annual rainfall of 1200-1600 mm, and whose mean maximum and minimum temperatures are similar to, or greater than, those of 1200 m in Malawi (Savory and Thomas, 1977).
It was thought worthwhile to test Leucaena, initially on a small scale, for its adaptability and fodder performance at one of these mid-altitude, sub-humid areas. The results of the first year's work are reported here.
Leucaena has been planted at Bako Research Station (9°8'N: 37°5'E), 255 km by road due west of Addis Ababa. The attitude is 1650 m. Monthly rainfall and temperatures for 1979 together with their long-term means are given in Table 1. Rainfall distribution is unimodal with an average of 80.3% of the mean total occurring between May and September inclusive. Useful rain sometimes falls in April and October and an effective `short rains' in March can occur with a probability of one year in four. In general an active growth season of six to seven months may be expected during which mean maximum and minimum air temperatures average 26.0°C and 13.6°C, respectively.
Table 1. 1979 rainfall and air temperatures for Bako.
Month |
Rainfall mm |
No. of rainy days |
Air temperatures °C | |
Mean Max |
Mean. Min | |||
January |
33.4 (13.2)a |
3 (3.0)a |
27.0 (29.4)a |
12.6 (10.1)a |
February |
62.1 (20.5) |
4 (4.2) |
29.4 (30.7) |
12.4 (11.8) |
March |
29.1 (46.3) |
7 (7.6) |
31.1 (31.3) |
13.7 (13.5) |
April |
11.7 ( 55.7) |
3 (9.2) |
31.4 (31.0) |
13.3 (15.0) |
May |
207.1 (169.9) |
17 (17.0) |
28.3 (28.7) |
15.8 (14.5) |
June |
238.6 (204.9) |
24 (23.4) |
25.5 (25.9) |
15.2 (14.1) |
July |
264.0 (265.3) |
27 (25.3) |
23.9 (23.8) |
14.9 (14.0) |
August |
238.1 (229.4) |
21 (22.2) |
24.5 (24.2) |
14.8 (13.8) |
September |
83.1 (146.9) |
15 (16.6) |
25.5 (25.3) |
14.1 (13.3) |
October |
43.2 (69.0) |
8 (6.5) |
27.4 (27.8) |
12.4 (12.1) |
November |
0.5 (28.2) |
1 (2.7) |
28.4 (28.2) |
11.1 (10.3) |
December |
6.1 (15.7) |
4 (2.6) |
28.7 (28.9) |
11.5 ( 9.1) |
Total |
1217.0 (1265.0) |
134 (140.3) |
||
Mean |
27.6 (27.9) |
13.7 (12.6) | ||
a Mean values (1961–1979) are denoted in parentheses.
From May through October sunshine hours/day average 5 with a minimum of 3.1 occurring in July and August. Wind speeds are low throughout the year, averaging 1.08 km/hr. Mean daily evaporation (Class A pan) ranges from a minimum of 2.92 mm in July and August to a maximum of 6.54 mm in April. The year round daily average is 4.51 mm. Occasional light frosts can occur in valley bottoms in November through January, but not elsewhere as far as is known.
The Leucaena was grown on a red-brown, sandy clay loam oxisol of moderate to good permeability. Previous analysis of similar nearby soils indicate a pH of 5.5 to 6, cation exchange capacity of 12 to 25 meg/ 100 g, and 11.8 to 18.7 ppm available phosphorus (Olsen method).
Seeds of the cultivars Cunningham and Peru from Malawi together with an unnamed variety (hereafter referred to as ( 'X' ) from Australia, were treated with hot water at 80°C for two minutes prior to planting in perforated plastic pots of 7.6 cm diameter and 20 cm length. The potting mixture was topsoil, sand and manure in the ratio of 4:4:1 by volume.
Seeds were planted at 2.5 cm depth on January 18, 1979; emergence percentages 18 days later were 71.6 for Cunningham, 75.6 for Peru and 65.3 for 'X'. The pots were watered daily for the first six weeks, and thereafter thrice weekly until transplanting.
Some seeds of all three cultivars were coated with soil containing CB 81 rhyzobium prior to planting; further groups of seedlings were separately treated with rhyzobium strains CB 81, NGR 8, and NGR 135, carried on an agar base, which was dissolved in water and applied by watering can one month after planting. A few seedlings received no inoculum. Seedling growth was rapid. Two root and stem pruning were required prior to field transplanting. Termite attack was prevented by application of 1 g Aldrin (40% WP) per 100 seedlings applied in 10 litres of water and covered with a little potting mixture to prevent volatilization.
The seedlings were transplanted into trial plots on 10 May, 1979, shortly after the onset of the rains, at an interplant spacing of 15 cm with 100 cm between rows. The base of the pots was cut off and the sides slashed prior to placing the seedlings in trenches 15 cm deep containing Di-ammonium phosphate fertilizer at the rate of 200 kg/ha.
The bushes were harvested by cutting the main stems 30 cm above ground level. Any lateral branches below this height were cut back to 20 cm from the main stem.
The three cultivars were planted in randomized blocks with three replications. Each plot consisted of three rows of length 5 m. The centre row was harvested for yield determination, plant analysis (stem and branches, twigs, arid leaves), and protein analysis of each component.
The three cultivars were factorially combined with the three agar-based rhyzobia to give single plots in a Graeco-Latin square design. There were three rows of length 2.25 m per plot. The centre row was used for yield determinations. In addition, two 5 m length single rows each of cultivators. Cunningham and Peru seedlings with and without soil based CB 81 inoculum were planted.
Three 5 m rows of Cunningham, inoculated with soil based CB 81 rhyzobium, were planted at the same time as the potted seedlings were transplanted. Yields were compared.
Whole freshly cut branches were offered to cattle and sheep. The time required for acceptance and the percentage eaten were recorded.
The first harvest was taken when Peru, the most rapidly maturing of the three cultivars, had just started pod formation; Cunningham and 'X' were then still in the flowering stage. This somewhat late initial cutting was taken to allow maximum root development prior to the dry season. All cultivars were approximately 1.8 m tall at first harvest. The plants were cut again some ten weeks later having received a further 6.6 mm of rain. Leaves at this stage showed signs of wilting.
Table 2 contains the yield data of both harvests for the trials comparing cultivars and comparing rhyzobial strains, together with details of the whole plant analysis (stem plus branches, twigs, and leaves) by fresh weight and crude protein percentage.
Table 2. Performance of Leucaena at Bako
Cultivar |
Peru |
Cunningham |
"X" |
Mean |
SE a |
CV%b |
Comparison of cultivars Yield Data | ||||||
1st harvest 24/10/79 Yield (t/ha DM) |
|
|
|
|
|
|
Whole plant DM% |
32.4 |
32.7 |
32.3 |
|||
2nd harvest 10/1/80 Yield (t/ha DM) |
1.19 |
0.78 |
1.43 |
1.13 |
0.18 |
27.6 |
Whole plant DM% |
37.2 |
28.6 |
35.8 |
|||
Total yield 1st and 2nd harvest (t/ha DM) |
7.69 |
6.93 |
9.38 |
8.00 |
0.71 |
15.4 |
Whole plant analysis | ||||||
1st harvest. Fresh wt. basis Main stems and branches% |
|
|
|
|
||
Twigs% |
11.0 |
12.6 |
15.0 |
15.0 |
12.9 |
|
Leaves% |
58.0 |
59.3 |
59.6 |
59.1 |
||
Crude protein% DM basis. | ||||||
Main stems and branches |
|
|
|
|
||
Twigs |
6.4. |
6.7 |
7.0 |
6.7 |
||
Leaves |
19.1 |
19.7 |
19.1 |
19.3 |
||
2nd harvest. Fresh wt basis | ||||||
Twigs% |
22.6 |
14.8 |
22.5 |
21.0 |
||
Leaves % |
77.4 |
85.2 |
74.4 |
79.0 |
||
Comparison of rhyzobial strains | ||||||
Total yields 1st and 2nd harvest (t/ha DM) |
||||||
treated with: CB 81 |
8.06 |
9.56 |
9.45 |
9.02 |
||
NGR 8 |
7.10 |
7.56 |
11.34 |
8.75 |
1.23 |
13.1 |
NGR 135 |
10.56 |
12.49 |
8.46 |
10.50 |
||
a Standard error. (= standard deviation of the mean).
b Coefficient or variation.
There were no significant differences in yield between the three cultivars for either harvest or for the total of both harvests. Fresh yields averaged 21.2 and 3.3 t/ha for the first and second harvests, respectively, for the three cultivars.
At the first harvest, leaves, which included the rachae and pinnae, constituted nearly 60% of the total fresh weight of the whole plant, with a crude protein value averaging 19.3%. There was little difference between cultivars in either percentage or crude protein values. Twigs, mainly secondary and tertiary branches of diameter 0.3 cm or less, averaged 12.9% of the total fresh weight. Branches and main stems, ranging in diameter from 1.5 to 0.3 cm, averaged 28% of the total plant weight and contained 4.4% crude protein.
Leaves, twigs and stems/branches had mean dry matter (DM) percentages of 31.3, 33.3 and 35, respectively, and thus the whole plant analysis on a dry matter basis did not differ markedly from that on a fresh weight basis.
Regrowth at the second harvest consisted only of leaves and twigs.
There was no significant difference in yield attributable to the nodulation effect of any of the rhyzobial strains. Root examination revealed that most of the plants had some active nodules but at a relatively low concentration. Neither the agar-based nor the soil-based rhyzobia appeared to have been very effective in promoting nodulation, although both were stored under refrigeration until usage. Some inoculum viability may have been lost in transit from Malawi to Ethiopia. Cultivar `X' appeared to have less well nodulated roots than Peru and Cunningham. Single row comparisons with cultivars Peru and Cunningham between seedlings given CB 81 rhyzobia and those given no inoculum showed no appreciable visible or yield differences.
No visible nitrogen deficiency symptoms have been apparent so far. However, all seedlings received 36 kg N/ha, resulting from fertilizing with Di-ammonium phosphate, and this may have been sufficient to prevent N deficiency symptoms appearing in the first year of growth.
Cunningham bushes planted from seed at the start of the rains were 50 to 70 cm in height by the first harvest in October, and gave a DM yield of approximately 1.5 t/ha. Regrowth during the dry season has been reasonable. Although yields of direct-planted Leucaena would be very much less in the first year than those obtained from transplanted seedlings grown under irrigation, the saving in cost, water and labour, could make the former method more worthwhile for small scale farmers.
Acceptance of freshly cut Leucaena was immediate with mature zebu and crossbred bulls. Calves and sheep required one day of familiarization before eating the material: 63.2% of the fresh weight of cultivar Cunningham was eaten within 30 minutes by local Horro six-month-old lambs. All the leaves and some of the more tender twigs were consumed. The remaining, uneaten, materials could provide useful kindling and fuel wood.
No diseases have been apparent on the plants up to the present. Untreated seedlings, both potted and transplanted, were very susceptible to attack by termites who ate the bark of the lower stems. Aldrin application to the pots gave good protection even after transplanting. However, the first indications of further termite attack were seen at the first harvest and 0.5 g Aldrin (40% WP) per metre of row was watered on and immediately covered with soil. No further damage has occurred. Chain link fencing has been necessary to prevent nocturnal browsing by bushbuck and possibly porcupine.
The overall mean yields of 8.72 t/ha DM obtained in the first year of establishment, in which late season rainfall was appreciably less than usual, indicated that Leucaena can grow and yield successfully in the Bako environment. The lower altitudes and increased rainfall, up to a mean of 1600 mm per year, suggest that the plant should thrive in large parts of the Welega, Ilubabor and Kefa administrative regions of Ethiopia.
Modulation, although present, was not vigorous. The yields obtained should be ascribed, to some extent, to the initially applied fertilizer nitrogen. No conclusions can be drawn as yet either to the most effective rhyzobium or the most suitable cultivar for Bako conditions.
The author expresses his appreciation to the staff of the Pasture and Fodder Crops Section, Bako Research Station, and in particular to Messrs. Alemu Taddese, Tadesse Tekla Tsadik and Eshetu Begna for their assistance in conducting the trials.
Thanks are due to Mr. R. Savory, former Pasture Agronomist, FAO Assistance to Livestock Development Project, Malawi, who supplied the seeds, rhyzobium strains, and advice.
The soil and meteorological data were provided by Messrs. Asgelil Dibabie and Agessa Guttema, respectively.
National Academy of Sciences (1977). 'Leucaena: promising forage and tree crop for the tropics'. Washington, USA, Nat. Acad. Sciences.
Savory, R. and D. Thomas 1977). The pasture handbook for Malawi (2nd ed.) Lilongwe, Malawi, FAO.
Skerman, P. J. (1977). Tropical forage legumes. FAO Plant Production and Protection series, no. 2. Rome, FAO.
