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VII. Legume Nutrition Relative to Tropical Pasture Development

VII. Legume Nutrition Relative to Tropical Pasture Development

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28



E. M. HUTTON



The initial detailed research on soil nutrient deficiencies and nutrient

responses of legumes in coastal areas of northeastern Australia was done

by Andrew and Bryan (1955, 1958; Bryan and Andrew, 1955) in the

southern Wallum on very poor sandy acid soil near Beerwah, 40 miles

north of Brisbane. These soils are very deficient in P (3-6 ppm), Ca, and

K, as well as N. Depending on site, the limiting nutrients for plant growth

in descending order are P, N , Ca, K, S, Cu, Zn, Mo, and B. Effective

strains of rhizobia were obtained for white clover, P . luthyroides, and

the other test legumes which resulted in efficient nodulation and elimination of the need for N. Relatively low applications of calcium carbonate

promoted good legume growth, as the response was due to Ca nutrition,

not to the soil pH factor. Overliming could adversely affect pH and availability of elements like Cu and Zn. White clover needs more Ca than

silverleaf desmodium and responded significantly to soil additions of

Cu which did not increase growth of silverleaf. On the lateritic podzolic

soil type, maximum response of white clover to S occurred only when 200

lb of Ca per acre was applied. Under grazing and with adequate fertilizer,

white clover persists on the wet gley soils and not on the dry podzolics

whereas silverleaf persists on both soil types. For pasture establishment

on these poor southern Wallum areas, the fertilizer mixture needed per

acre comprises 5 cwt superphosphate, 5 cwt calcium carbonate, 1 cwt

potassium chloride, 7 Ib copper sulfate, 7 Ib zinc sulfate, 7 Ib borax, and

2 oz elemental Mo. This is a heavy initial dressing, but the subsequent

annual requirement is only 2 cwt superphosphate and 1 cwt potassium

chloride per acre. A similar fertilizer regime is needed to develop improved legume-based pastures in the northern Wallum extending in

Queensland from Maryborough to just north of Bundaberg (T. R. Evans,

1967). Altogether the sandy infertile coastal lowlands of the Wallum

cover some 2 million acres. Cost of developing improved pastures here

is high, but beef production is profitable because of a good rainfall (4065 inches), long growing season, and maintenance of a high stocking rate

of a beast per acre. The Wallum is only a small fraction of the vast area

in northern Australia awaiting development through improved pastures

(J. G. Davies and Eyles, 1965). Much of the area can be developed more

cheaply than the Wallum and requires only a suitable legume-based pasture and annual application of 1-2 cwt of superphosphate per acre, use

of Mo where deficient, and the occasional inclusion of a potassic fertilizer.

Following the preliminary Wallum work, Andrew ( 1960) found that

additions of sodium phosphate, potassium chloride, and calcium carbonate each increased the yield of white clover in a humic gley soil and

increased its P, K, and Ca contents, respectively. Yield of clover was



TROPICAL PASTURES



29



closely correlated with its P content and also its K and Ca contents. The

critical percentage (sufficiency in the plant for maximum growth) was

0.23 for P, 1.1 for K, and I .O for Ca. There was no correlation between

P deficiency symptoms and P content. A close correlation between K

deficiency symptoms and yield and K content was obtained, and Ca deficiency symptoms appeared only when Ca was omitted. Responses of a

number of legumes to Cu were studied by Andrew and Thorne ( I 962)

and Andrew ( 1963a). Srylosanrhes guyanensis (incorrectly S. bojeri)

was one of the most sensitive to Cu deficiency, and silverleaf desmodium

and white clover were the least sensitive. For maximal growth, sensitive

species required 4 lb of copper sulfate per acre and insensitive species,

0.5 lb per acre. The sensitive species were less efficient in extracting Cu.

A Cu concentration in legumes above 5 ppm is satisfactory and below

4 ppm indicates deficiency. With the exception of S. guyanensis, Cu

deficiency symptoms occurred first in young growth as partial wilting

and necrosis of younger leaves and shoots. Concave curling of leaflets

and tip necrosis was general in all Cu-deficient species.

Since P is so vital in legume nutrition and development of tropical

pastures, Andrew and Robins (1 969a,b) examined its effect on growth and

chemical composition of the main tropical legumes. Hunter River lucerne,

a temperate legume, was included because of its increasing use in the subtropics. All species responded to P, and Cooper glycine and greenleaf

desmodium were most responsive; although Townsville stylo and Miles

lotononis were least responsive, they accumulated most P in plant tops.

Townsville stylo, Hunter River lucerne, and Miles lotononis gave maximum yields at approximately 4 cwt superphosphate per acre, whereas

the more responsive species Cooper glycine, greenleaf and silverleaf

desmodium, siratro, and Murray lathyroides required up to 10 cwt per

acre to achieve maximum production. Critical P percentages in the tops

of Murray lathyroides, siratro, Townsville stylo, centro, Cooper glycine,

Miles lotononis, Hunter River lucerne, silverleaf desmodium, greenleaf

desmodium, and Dalrymple vigna at immediate preflowering were 0.20,

0.24, 0.17, 0.16, 0.23, 0.17, 0.24, 0.23,0.22, and 0.25, respectively. The

N concentrations in plant tops were increased by P supply, and there was

a good correlation between N and P levels in plant tops. Phosphorus

applications beyond that necessary to produce maximum dry matter

production continued to increase N concentration in plant tops; this

poses the question, should a pasture be fertilized for maximum dry matter or nitrogen production? When sodium dihydrogen phosphate was

applied, Na concentration in Dalrymple vigna, Hunter River lucerne,

and Miles lotononis was increased. Use of monocalcium phosphate did



30



E. M. HUTTON



not increase plant Ca levels but increased Mg in Murray lathyroides and

siratro. Increases in P supply reduced K concentration in most species,

which was partly compensated by increased Mg and Ca concentrations.

Throughout siratro and Murray lathyroides were relatively high in Mg,

Miles lotononis and greenleaf desmodium in K, Dalrymple vigna, Miles

lotononis, Hunter River lucerne, and Murray lathyroides in Na, and

centro and Townsville stylo in Ca.

In Andrew and Robins’ experiments (1969a,b) relative growth rate

of Townsville stylo was superior to that of the other species when grown

in soils low in available P. This was due to its ability to absorb greater

quantities of P from such soils and supports the work of Andrew (1966a).

He made a kinetic analysis of P absorption from solutions by excised

roots of Townsville stylo, Murray lathyroides, silverleaf desmodium,

Hunter River lucerne, and barley. Townsville stylo absorbed greater

quantities of P per unit weight of root per unit time than the other species

at both low and high P concentrations. Figure 5 gives the relationship

between P uptake and time at a low phosphate substrate concentration

(1 X 10+ M KH2POJ. The relatively low P critical percentage and greater

efficiency of Townsville stylo in extracting P is clearly shown and explains its ability to grow and spread on soils with only 3- 10 ppm of available P. Field evidence indicates that other Stylosanthes species possess

this characteristic.

Andrew and Robins (1969c,d) studied the effects of potassium chloride

on the growth and chemical composition of eight tropical and four temperate pasture legumes. They all gave a marked dry matter response to

K but increase in K concentration of the tops occurred only at medium

to high rates of application. Miles lotononis, greenleaf desmodium, and

the four temperates were high in K and Townsville stylo was low. Critical percentages of K in tops of Murray lathyroides, siratro, greenleaf,

and silverleaf desmodiums, Townsville stylo, Miles lotononis, centro,

Cooper glycine, Hunter River lucerne, Jemalong barrel medic, irrigation

white clover, and Palestine strawberry clover were, respectively, 0.75,

0.75, 0.80,0.72,0.60,0.90,0.75,0.80,1.2, 1.0, 1.0,and 1.0. Application

of potassium had little effect on total cation content. The effect on plant

Ca in Murray lathyroides, siratro, and Hunter River lucerne was small

compared to that in the others. Townsville stylo had the highest Ca concentration, and the four temperates, greenleaf desmodium, and centro had

low concentrations. Except in centro, Jemalong barrel medic, and Palestine strawberry clover, potassium chloride depressed Mg uptake. Murray

lathyroides and siratro were high in Mg; centro and Palestine strawberry

clover were low. Substantial reductions in Na concentrations occurred



31



TROPICAL PASTURES



70



60



-



--



"'05 0 x



c

0



e

em



40-



L



a,



a



U



300



m



n



ln



a,



s



20-



10



-



5



0



2



4



6



8



1



20



0



Time (min)



FIG. 5. Relationship of phosphorus uptake to time in excised roots of Stylosanthes

humilis ( A ) , Phaseolus lathyroides (0). Desmodium uncinatum

lucerne (O), and

barley (0).Substrate concentration, 1 X

M KH2P04. (From Andrew and Robins,

I969a,b).



(a),



in all species except the desmodiums and centro. The temperates, particularly Palestine strawberry clover, accumulated more Na than the

tropicals; Miles lotononis, Murray lathyroides, and Townsville stylo

were the highest in the tropicals. Species with marked cation interactions

were those with high uptakes of Mg and Na. With potassium chloride

application plant concentration of N was unaffected, P was decreased,

and chloride increased. The desmodiums accumulated chloride to high

levels which depressed growth.

Manganese and Al excess is often present in the poor acid soils of northern Australia. In preliminary experiments Andrew (1963b, 1966b) found



32



E. M. HUTTON



that Townsville stylo and Miles lotononis were quite tolerant to excess

Mn and A1 compared with the sensitive glycine and Hunter River lucerne.

Andrew and Hegarty ( 1969) compared the response of eight tropical and

four temperate legumes to excess Mn in water culture and found that the

tropicals were as much affected as the temperates. The tolerant species

produced no more dry matter than the less tolerant. Manganese concentrations reached in Townsville stylo were about twice those in Miles

lotononis, yet both species were among the most tolerant. Among the

least tolerant, Mn uptake by P . atropurpureus greatly exceeded that of

Tinaroo glycine. Of the other species centro was tolerant while Murray

lathyroides. leucaena, and silverleaf desmodium were intermediate in

response. The results indicated that the relative tolerance of species depended partly on retention of Mn within the root system. Manganese

treatments had little effect on the Ca and N levels in the tops of most

species.

Since superphosphate is the principal fertilizer used to correct the

gross deficiency of P and S in coastal and subcoastal soils of northern

Australia, studies on its effects on pasture components at different sites in

this extensive area are necessary. These aspects were investigated by

Truong et al. (1967) and R. K. Jones (1968) on solodic soils in southeastern and northeastern Queensland, respectively. Truong er al. ( 1967)

found that on poor solodic soil (5-9 ppm P) at Beaudesert with nil P,

siratro was stunted and the tops contained 0.18% P and that with P applications up to the equivalent of 4 cwt superphosphate per acre, dry

matter yields increased and the tops contained 0.22% P. White clover

also responded to P, and the P levels in the tops at nil P and the equivalent of 4 cwt superphosphate per acre were 0.15% and 0.2 I %, respectively. Siratro and white clover also responded to Mo. In addition, white

clover responded to calcium carbonate and S but the application of small

amounts of Mo removed the need for calcium carbonate. With white

clover interactions occurred between Mo and S and also S and calcium

carbonate. In R. K. Jones’ experiments ( 1 968), Townsville stylo growing

on a solodic soil responded markedly to superphosphate. Applying 3 cwt

per acre of superphosphate in the first year only rather than annual

amounts of 1 cwt per acre gave higher yields of dry matter over a threeyear period. Splitting the application into annual dressings gave slightly

higher yields of N and P per acre for the three years. It is apparent that

superphosphate has a marked residual effect in this soil. Critical value

for P in Townsville stylo tops varied from 0.16 to 0.17% similar to that

found by Andrew and Robins (1969a). It was of interest that seed P levels

appeared to be related to fertilizer history and P status of the plants.



TROPICAL PASTURES



33



Andrew ( 1965, 1968) reviewed diagnostic techniques for determining

mineral status of tropical pasture plants and the problems in their use. He

emphasized that foliar analysis is a relative approach, the observed value

being related to a standard critical percentage which must be determined

for the different species under optimum growth conditions in which secondary deficiencies and toxicities are corrected. With legumes, unless

they are well supplied with nitrogen, either mineral or symbiotic, there is

no point in establishing their critical values for elements like P, K, and

Mg. The critical percentages for the various nutrients can be applied to

field-grown material only under strict sampling conditions which relate

to stage of growth, part of plant, environmental factors, and freedom from

undue insect and pathogen damage. For correct interpretation of the foliar

anslysis of field material relative to critical values, an appreciation of the

interactions of N , P,S, and K in plant nutrition is required.

The results coming forward from research on nutrition of pasture legumes if properly applied will ensure maximum production of dry matter

and protein from legume-based pastures in the different tropical environments. Also, they will give a lead to animal nutritionists concerned with

the relationship between the mineral balance of pastures and animal production. Plant breeders and geneticists could well accept the challenge

presented by the efficient utilization of P by Townsville stylo and endeavor to breed this character into a number of the other tropical legumes.

VIII. Undesirable Compounds in Tropical Legumes



A. ESTROGENS

A N D SUBSTANCES CAUSING

BLOATA N D MILKTAINTS

Analyses and biological tests have indicated that estrogens and allied

compounds are at a low level in the tropical legumes and are unlikely to

reduce fertility. The only tropical legume known to cause bloat is Rongai

lablab (Hamilton and Ruth, 1968), and then only occasionally when it is

young and growing rapidly. Perhaps tropical legumes are free from the

bloat-inducing 18 S protein of McArthur and Miltimore ( 1966).

Milk from dairy cows fed only Rongai lablab or Nandi setaria had a

strong odor and taint and was considered unacceptable on receipt, but

pasteurization made it acceptable (Hamilton et al., 1969). The milk from

a sole diet of leucaena was acceptable without treatment.



B. MIMOSINE

Yoshida ( 1944) showed that leucaena contained mimosine, but no

effects on reproduction were obtained in dairy cows fed only leucaena



34



E. M . HUTTON



and concentrates for several years at the Hawaiian Agricultural Experiment Station (Anonymous, 1948). Mimosine is an undesirable depressant

of cell division (Hegarty et al., 1964a) and accounts for about 0.5% of

the N of leucaena herbage. It has been known for some time that feeding

leucaena affects reproduction in monogastric animals like rabbits (Willet et d., 1947)and sows (Wayman and Iwanaga, 1957).

Hegarty et al. ( 1 964b) developed methods for the extraction and determination of mimosine present in leucaena leaves and urine. This enabled

them to study the reaction of sheep to consumption of leucaena and mimosine. Sheep shed their fleeces on a sole diet of leucaena because the mimosine in it suppressed mitotic activity in the follicle bulb of the growing

wool fiber and caused follicle degeneration. Follicle regeneration occurred

when sheep were taken off leucaena but occurred also in animals on a

continuing leucaena diet. During leucaena feeding, only small quantities

of mimosine were excreted, most being degraded by rumen flora to 3,4dihydroxypyridine, the main urine component. Sheep cannot detoxicate

mimosine after absorption beyond the rumen. It was found that sheep

could be conditioned to a sole diet of leucaena without ill effect due to

increased detoxication from adaptation of rumen microorganisms.

In Queensland continuous grazing of leucaena pastures for extended

periods has adversely affected steers. Symptoms include shedding of

hair on the rump and tail and loss of weight indicating incomplete breakdown of mimosine in the rumen. Hamilton er al. (1 970) made a close

study of reproduction in dairy heifers fed a complete diet of this legume.

Leucaena did not affect estrus cycle length, conception rate, gestation

length, calving rate, milk production or composition. However, mild

incoordination occurred briefly during gestation in some cows and birth

weight of calves from cows fed leucaena was lower than of control calves.

There was no residual effect of leucaena on calf growth rate, as the resulting calves grew at the same rate as the controls.

C. INDOSPICINE

Indigofera spicata (syn. I . endecaphylla) is found in a number of areas

including India, Ceylon, Indonesia, Philippines, Hawaii, Central America,

Brazil, and west Africa, and is regarded as a promising pasture legume because of its vigorous, prostrate, stoloniferous habit and high level of N

fixation (Henzell, 1962). Trials in the early 1950’s with several introductions at coastal sites in southeastern Queensland confirmed the potential of this legume. However, its widespread use was prevented by the

work of Emmel and Ritchey (1941) and Nordfeldt et al. (1952), who fed



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VII. Legume Nutrition Relative to Tropical Pasture Development

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