Forage yield, mineral composition, nutrient cycling and ameliorating effects of Karnal grass (Leptochloa fusca) grown with mesquite (Prosopis juliflora) in a highly alkaline soil

FieM Crops Research, 26 ( 1991 ) 45-55 45 Elsevier Science Publishers B.V., Amsterdam

Forage yield, mineral composition, nutrient cycling and ameliorating effects of Karnal grass

( Leptochloa fusca ) grown with mesquite (Prosopis juliflora ) in a highly alkaline soil

Gurbachan Singh, H.S. Gill, I.P. Abrol and S.S. Cheema Central Soil Salinity Research Institute, Karnalo 132001, India

(Accepted 26 March 1990)

ABSTRACT

Singh, G., Gill, H.S., Abrol, I.P. and Cheema, S.S., 1991. Forage yield, mineral composition, nutrient cycling and ameliorating effects of Karnal grass (Leptochloafusca) grown with mesquite (Prosopis juliflora) in a highly alkaline soil. Field Crops Res., 26: 45-55.

A field study was initiated in July 1984 in the Karnal district of Haryana, India to examine the forage production, mineral composition, nutrient cycling and reclaiming effects of Karnal grass (Lep- tochloa fusca (L) Kunth) grown in association with mesquite (Prosopis juliflora (SW) DC) in an agroforestry system on an extremely alkaline soil (pH 10.4, exchangeable sodium percentage 90). Karnal grass inter-crop gave 47 t ha- ~ green forage in 15 cuttings without any amendment in a growth- period of about 50 months, proving its potential as a primary colonizer of abandoned alkali lands. The inorganic chemical composition of the grass, including trace elements Fe, Mn, Zn and Cu, indi- cated that the grass may be valuable fodder under these adverse edaphic conditions. Removal of 453 kg ha- t of N, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu in the crop in a 2-year growth-period did not result in any site depletion in available nutrients. Growing of Karnal grass with mesquite for a period of 52 months reduced pH and EC and improved organic C, available N and water intake capacity of a barren alkali soil. Further, the soil was improved to the extent that some moderately salt-tolerant crops such as Trifoliurn resupinatum, T. alexandrinum and Melilotus denticulata have been grown successfully after ploughing-under of Karnai grass. This study suggested that the biological approach for utilization and improvement of abandoned alkali soils is feasible. Under certain specific situations where the amendments either are not available or are costly, this approach may, indeed, be the only economic method of utilization of these marginal land resources.

I N T R O D U C T I O N

Sodic (alkali) soils are widespread in the world (Szabolcs, 1977 ); in India they occur mainly in the Indo-Gangetic alluvial plains, where they are esti- mated to cover about 2.5 × 106 ha (Abrol and Bhumbla, 1971 ). These soils are confined to areas receiving an annual rainfall between 550 and 1000 mm, and are characterized by the presence of high exchangeable sodium, high pH

0378-4290/91/$03.50 © 1991 - - Elsevier Science Publishers B.V.

46 G. SINGH ET AL.

and poor physical properties. Most of these soils support no vegetation, or allow the growth of only a few wild species such as Sporobolus marginatus, S. diander, Desmostachya bipinnata and Suaeda maritima (Bhumbla et al., 1972).

The improvement of such soils by addition of calcium is universally rec- ognized. However, exogenous supply of Ca is quite expensive. Fortunately, sodic soils contain high levels of calcium carbonate. This research programme has been designed to explore the possibilities of using this native source of Ca for amelioration of sodic soils. Calculation indicates that 1% CaCO3 in the soil would be equivalent to 67.5 t gypsum ha- x 30 cm of soil if this native CaCO3 could be solubilized. An ideal method for doing so could be through the initiation of biological activity associated with the cultivation of salt-tol- erant plants.

Leptochloa (Diplachne) fusca (L) P. Beauv., known in India as karnal grass (Kumar and Abrol, 1983, 1984), as kallar grass in Pakistan (Sandhu et al., 1981 ) and Australian grass in Australia (Hussain and Hussain, 1970), is a perennial, palatable forage grass tolerant of soil salinity and sodicity. Hussain and Hussain (1970) reported that this grass was able to grow in a soil with a saturation electrical conductivity (ECe) of 22.3 dSm-1 and a pH of 9.8. Be- cause of its C4 system of photosynthesis (Zafar and Malik, 1984), a high tolerance to sodicity (Aslam et al., 1979; Sandhu et al., 1981 ) and associative nitrogen fixation (Zafar et al., 1986), kallar grass was able to produce reason- able amount ofbiomass on salt-affected soils with very low inputs. Hence this grass might be useful for colonizing barren sodic soils for biomass production and soil amelioration. In this study, we explored the possibilities of growing this grass in association with mesquite (Prosopis juliflora (SW) DC) in an agroforestry system.

M A T E R I A L S A N D M E T H O D S

This study was conducted at the Central Soil Salinity Research Institute, Karnal (29°29'N, 76°56'E). The site was on common village land which had previously been used for grazing but which had gone out of cultivation because of severe problems with alkalinity. It is typical of the alkaline soils of the sub-tropical semi-arid monsoon regions. The average annual rainfall of the area is about 750 mm, about 80% of which is received during June, July and August. Pan evaporation exceeds precipitation throughout the year ex- cept in the monsoon months. The ground watertable varied from 5 or 6 m during the summer to 2 or 3 m during the rainy season.

The soils are characterized by high exchangeable sodium levels, high pH throughout the profile, dispersed soil conditions, poor physical properties and a dense impermeable calcium horizon at a depth of about 1 m (Table 1 ). The type of soil has been classified as Aquic Natrustalf (Bhargava et al., 1980).

CHARACTERISTICS OF KARNAL GRASS AND MESQUITE IN ALKALINITE SOIL

TABLE 1

Soil properties of the experimental site

47

Soil Mechanical analysis (%) pH EC ~ depth (dSm- J ) (cm)

Sand Silt Clay

ESP 2 o c Available nutrients (%) (kg ha -~ )

N P K

0- 15 51.4 28.3 20.3 10.3 2.3 94 15- 30 43.5 31.5 25.3 10.3 1.9 93 30- 60 42.8 32.0 25.2 10.1 1.5 90 60- 90 37.0 34.2 28.8 10.2 1.4 91 90-120 32.4 40.5 27.1 10.2 1.3 92

0.17 82 35 533 0.12 73 28 488 0.10 60 20 440 0. I0 42 18 356 0.10 34 14 300

~Measured in 1 : 2 soil: water suspension. 2Exchangeable sodium percent.

TABLE2

Effect of mesquite canopies on green forage yield of Karnal grass intercrop

Treatment for planting mesquite Forage yield (t ha-~ ) Total

Planting technique Filling mixture ~ 1984 1985 1986 1987 1988

Trench OS 1.5 11.7 10.4 9.4 17.0 50.0 Trench G 2.4 14.3 12.3 7.7 14.1 50.8 Trench G + R H 1.6 13.4 9.2 7.0 13.6 44.8 Trench G + F Y M 1.7 10.7 9.6 6.9 11.7 40.6 Pit G 2.0 12.0 9.3 7.2 12.2 42.8 Auger G 3.7 16.4 10.1 7.3 12.3 49.8 Average 2.2 13.1 10.1 7.6 13.5 46.5 LSDo.05 0.8 4.3 N.S. N.S. 2.8 4.8

~OS, G, G + R H and G+FYM refer to original soil, gypsum, gypsum plus rice husk, and gypsum plus farm yard manure, respectively.

A randomized block design was used, with four replicates and a plot size of 24 m × 5 m. Mesquite was planted at 3-m intervals in 5-m-wide rows. Six selected treatments (Table 2 ) were compared for planting mesquite. The per- formance of mesquite was further tested under two situations with Karnal grass in the inter-row space, and without grass. In the present paper, data related to the grass component of this agroforestry system are presented.

Karnal grass was transplanted through root cuttings in dry conditions in the first week of August 1984. The first irrigation was given immediately after planting, and subsequent irrigations were applied as and when required, at intervals of 15-20 days in summer and 25-30 days after the July-September monsoon season. Good quality water from a shallow tubewell was used. Kar- nal grass was planted at a spacing of 30 cm × 20 cm. In a growth period of 52

48 G. SINGH ET AL.

months, 15 cuts were taken: in 1984, there was only one cut ( 13 November); in 1985, 4 cuts (3 May, 10 July, 9 August and 16 October); in 1986, three cuts (2 July, 22 August and 24 September); in 1987, three cuts (29 May, 22 August and 24 September) and in 1988, four cuts (29 July, 27 August, 15 September and 28 October) were taken. The grass was cut at about 5 cm above ground level.

For chemical analysis, whole-plant grass samples from each plot consisting of edible succulent plant parts were taken at random just before harvest. The samples were washed with tap water, dilute acid, and then with single- and double-distilled water. They were then air- and oven-dried at 70 ° C, ground in a Wiley steel mill, passed through a 16-mash sieve, and finally collected in polythene bags. The di-acid- (HNO3:HC104 in a ratio of 3: 1 ) digested plant samples were analysed for Na and K by flame photometer and for Ca, Mg, Fe, Mn, Zn and Cu with a Pye Unicam Atomic Absorption Spectrophotome- ter. Phosphorus was determined by vanado-molybdo-phosphoric-yellow col- our method (Jackson, 1967) and sulphur by the turbidity method (Mas- soumi and Cornfield, 1963 ) with a Spectonic 21 spectrophotometer. Total N was determined with a Kjeltic-II automatic nitrogen analyser.

Soil samples were taken 22 and 52 months after planting to investigate any changes in soil properties as a result of grass growth. Samples were taken from 0-15 cm and 15-30 cm layers of the soil profile. The samples were oven- dried, ground, passed through a 2-mm sieve and stored in polythene bags for analysis. The pH and EC were determined in a 1:2 soil: water suspension, organic C by the rapid titration method (Walkley and Black, 1934), available N by alkaline potassium permanaganate method (Subbiah and Asija, 1956 ), available P by sodium carbonate extraction method (Olsen et al., 1954) and available K by the ammonium acetate extraction method (Merwin and Peach, 1951 ). Infiltration rates were determined in the field using infiltrometer rings.

RESULTS A N D DISCUSSION

Forage yield

Green forage yield in 15 cuts in a growth-period of about 50 months is reported in Table 2. Total forage yield varied from 40.6 to 50.8 t ha- 1. In all years, Karnal grass produced the best yield in cuts taken during July and Au- gust. During these months the rainfall was plentiful, and mean maximum temperatures were 30-33 ° C. These conditions appear to be congenial for the growth of this species. Bhumbla et al. ( 1972 ) and Kumar et al. (1980) have reported that this grass grows naturally in low-lying sodic soil areas, where rain water accumulates. In a pot experiment, Kumar and Abrol (1979a,b) found that the yield of Karnal grass improved in response to an increased period of flooding (up to 8 days), indicating that it was able to tolerate poor

CHARACTERISTICS OF KARNAL GRASS AND MESQUITE IN ALKALINITE SOIL

TABLE 3

Growth parameters of 4-year-old mesquite trees under different treatments

49

Treatment for planting mesquite

Planting method Filling mixture

Height D~h ~ Dbh 2 (m) (cm) (cm)

Lopped woody biomass (t h a - ~ )

Trench OS 1.77 2.3 1.0 0.54 Trench G 4.32 5.6 3.3 3.70 Trench G + RH 5.23 8.1 4.5 5.49 Trench G + FYM 5.11 8.3 4.4 5.29 Pit G 4.38 6.9 3.6 4.40 Auger G 4.71 7.7 3.8 4.78 LSDo.o5 0.45 1.4 0.9 0.51

'Stem diameter at stump height, 5 cm above the ground. 2Stem diameter at breast height, 137 cm above the ground level.

soil physical conditions resulting from temporary waterlogging. The forage yield obtained in our studies was less than those reported elsewhere (Kumar and Abrol, 1983; Niazi and Malik, 1986 ). The higher yield in the latter was because the grass was grown as sole-crop under well-managed, irrigated and fertilized conditions. In our case, however, no input was added except irrigation.

Effect of mesquite canopies on inter-planted grass was variable. The grass yield was maximum where mesquite canopies were not fully developed. Mes- quite canopies were fully developed four years after planting where rice husk and farmyard manure (FYM) in conjunction with gypsum was added as a filling mixture (Table 3 ). In both these treatments, total forage yield was sig- nificantly less than with other planting techniques (Table 2 ). A similar rela- tionship between tree canopy cover and development of ground vegetation was observed by Grelan et al., ( 1972 ) and Saxena and Singh (1980).

Chemical composition of the grass

The mean chemical composition of the first eight cuttings indicated that the mean N, S and Na concentrations in the Karnal grass tended to decrease with successive cuttings, whereas there was a slight but gradual increase in K, P and Ca concentrations. The increase may have been due to increased con- centration in the soil solution, following conversion from non-labile to labile forms as a result of the biological activity of grass roots and the production of organic acids. The results are in agreement with those reported elsewhere (Bernstein and Pearson, 1956; Mehrotra and Das, 1973). It was noted that, as the Na concentration increased, the K concentration tended to decrease, suggesting that uptake of K was inhibited by the presence of Na and vice-

50 G. SINGH ET AL.

versa. These ions may be competing for specific sites on a particular ion car- rier for their uptake from the medium into the plant system. Among the mi- cronutrients, Fe concentration tended to decrease and Mn to increase with successive cuts, while Zn and Cu showed little change. The mean chemical compositions given in Table 4 suggest that this grass may be a useful forage for maintaining the mineral element balance of animals kept in salt-affected areas. These results confirm the findings of Wyn Jones (1982). Differential tolerance to alkalinity among plant species is reflected in preferential absorp- tion and accumulation of cations, principally sodium, in their leaves, roots and shoots (Khan and Yadav, 1962). Tolerant species take u15 large amounts of sodium, whereas sensitive ones may exclude it at the expense of Ca, Mg and K (Joshi et al., 1980). The presence of salt glands in the leaves of Karnal grass, capable of excreting sodium chloride, has also been reported (Joshi et al., 1980).

Nutrient uptake

Karnal grass extracted 114.3 kg sodium ha -1 from the soil in two years (Table 4). Similar results were reported by Grewal and Abrol ( 1986 ) under similar conditions, indicating that the grass may act as a precursor for the establishment of a plant succession, so enabling the improvement of aban- doned alkaline soil. On the other hand, the extraction of over 453 kg ha-1 of macro- and micro-nutrients from the soil in a period of about two years did not result in site depletion.

TABLE 4

Chemical composition and nutrient removal in first eight cuts of Karnal grass

Plant nutrient Chemical composition (mg g- ~ DW) Nutrient removal (kg ha - ~ )

1st cut 8th cut Mean

N 13.6 9.2 10.2 133.0 P 2.0 1.8 2.1 29.2 K 6.5 7.4 7.9 111.0 Ca 1.9 3.4 2.3 31.8 Mg 6.9 6.8 6.8 95.1 S 5.4 1.4 2.7 36.2 Na 15.2 5.8 8.5 114.3 Fe 1.5 0.7 0.9 12.0 Mn 0.2 0.3 0.3 4.0 Zn 0.03 0.02 0.02 0.34 Cu 0.02 0.02 0.02 0.28

CHARACTERISTICS OF KARNAL GRASS AND MESQUITE IN ALKALINITE SOIL 51

Effect on soil properties

Soil pH and E ¢

There was a marked fall in soil pH and EC during the experimental period, from their original values of 10.3 and 2.2, respectively (Table 5). After a growth-period of 52 months the soil pH and EC in the 0-15-cm soil layer fell to 9.4 and 0.42, respectively. Similar reductions in pH and EC were reported by Kumar and Abrol ( 1983, 1984) and Malik et al., (1986). The decrease in soil pH and EC might have been due to the root exudates and/or products of decomposition of grass litter. Moreover, the extensive root system of Karnal grass helped leaching of salts from the top layer. Ponnamperuma (1972) re- ported that pH of alkaline soils was highly sensitive to changes in the partial pressure of CO2. The CO2 released from the roots of growing plants facilitates the replacement of adsorbed Na in calcareous soils by solubilizing the native CaCO3 (Goertzen and Bowers, 1958; Chhabra and Abrol, 1977) and thus enhances the process of soil reclamation.

Organic carbon and available N Growing of Karnal grass resulted in marked increase in organic C and

available N build-up of a barren sodic soil. In a growth period of about 52 months, the organic C and available N in the 0-15-cm layer of the profile increased from 0.19% and 82 kg ha -1 to 0.43% and 139 kg ha -1 (Table 5). Similar increase was also observed in the 15-30-cm layer. This may have been due to an increase in biological activity in the previously barren soil as a result

TABLE 5

Effect of Karnal grass intercrop on important properties of the experimental site at 0, 22 and 52 months after planting

Soil property Depth Without grass With grass (cm)

0 22 52 0 22 52

ph 0-15 10.3 10.0 9.7 10.3 9,7 (1 :2 ) 15-30 10.3 10.0 9.9 10.4 10.0

EC 0-15 2.2 0.83 0.66 2.2 0,70 (dSm- l ) 15-30 1.5 0.84 0.78 2.0 0.94

Organic C 0-15 0.18 0.20 0.30 0.19 0.28 (%) 15-30 0.13 0.12 0.19 0.12 0.16

Available N 0-15 79 83 100 82 96 (kgha -J ) 15-30 73 73 84 73 82

Available P 0-15 35 33 30 35 29 (kg h a - ' ) 15-30 31 30 32 31 24

Available K 0-15 543 519 528 543 471 (kg ha-1 ) 15-30 490 480 478 490 430

9.4 9.8 0.42 0.63 0.43 0.21

139 104 22 19

402 412

52 G. SINGHET AL.

of grass root growth, litter fall and N fixation by the Karnal grass. Moreover, Karnal grass has a quite high lignin content, which may serve as a good sub- strate for the synthesis of humus. Growing of this grass may therefore raise the stable organic-matter level of these soils, which have low levels of humus due to its rapid turnover under the existing climatic conditions. The N-fixing bacteria associated with the roots of Karnal grass have been isolated and one of them identified as Klebsiella pneumoniea (Malik et al., 1982; Malik and Zafar, 1984; Zafar et al., 1986). It has now been established that nitrogen so fixed is, indeed, taken up by the grass to account for more than 50% of its N content (Malik and Zafar, 1985 ).

Available P and K The mean P and K contents in the soil measured at 22 and 52 months after

plating (MAP) were less where Karnal grass was grown in association with mesquite (Table 5 ). However, where it was not grown in the inter-space, a little change in available P and K status of soil was observed. The decrease in P and K in the former may probably be due to their removal through uptake by the Karnal grass in subsequent cuttings.

Effect on cumulative infiltration Growing of Karnal grass improved the permeability of the sodic soil. This

property would greatly help ameliorate sodic soils, as one of the main prob- lems in the management of such soils is the movement of moisture.

The downward penetration of water into the soil where Karnal grass had been growing for a period of more than four years is given in Table 6. The total water entering the soil in 48 h at 52 MAP was 54 mm in Karnal grass plots and only 24 mm in non-grass plots. The increased downward movement of water in grassed soil may possibly be due to improved soil conditions in terms of organic carbon and N build up, and reduced pH and E¢. Moreover,

TABLE 6

Effect of Karnal grass on water intake capacity of a sodic soil

Elapsed time (h) Cumulative infiltration ( ram) LSDo.o5

Original 22 MAP 1 a f t e r 52 MAP after soil planting planting

12 17 21 33 6 24 20 26 44 8 36 22 29 50 11 48 24 32 54 10

t Months after planting.

CHARACTERISTICS OF KARNAL GRASS AND MESQUITE IN ALKALIN1TE SOIL 53

Karnal grass roots open up the otherwise impermeable sodic soil, and water moves along the passages made by the roots.

Growing of other crops

Karnal grass was ploughed under in October 1988 (52 M A P ) and perform- ance of secondary colonizers, viz. Berseem (Trifolium alexandrinum), Per- sian clover ( T. resupinatum ), lucerne ( Medicago sativa ), Senji ( Melilotus denticulata) and oats (Arena sativa) was evaluated. Over a six-month growth- period, four cuts of Berseem, Persian clover and lucerne were taken on 15 February, 30 March, 18 April and 17 May 1989. However, only one cut of Senji and oats was taken, on 19 February and 21 April, respectively. Perform- ance of the crops was in the order: Persian clover, Berseem, lucerne, Senji and oats (Table 7). The study indicates that, after growing Karnal grass for a pe- riod of about four years, crops such as Persian clover, Berseem and Senji can be successfully grown on hitherto abandoned sodic soils.

This study concluded that the tolerance of Karnal grass to alkali conditions in the field, and its potential for forage production when planted in associa- tion with mesquite in an agroforestry system, make it a highly promising spe- cies for exploiting alkali lands not readily or economically reclaimed by con- ventional techniques. In certain specific situations where the soil is sodic and no good-quality water is available for irrigation, this biological approach may, indeed, be the only method of reclamation of these soils. These studies have confirmed the utility of Karnal grass not only as a primary colonizer of sodic soils but also as an ameliorative plant for the soil. These findings may be of importance in utilization of large tracts of salt-affected lands, not only in In- dia but also in other countries which face a similar problem of soil sodicity.

TABLE 7

Forage yield of secondary colonizers grown after ploughing under of Karnal grass

Crop Forage yield (t ha-1 ) Total

1 st cut 2nd cut 3rd cut 4th cut

Berseem 3.25 11.33 5.25 1.50 21.33 Lucerne 1.42 5.58 2.17 1.17 10.34 Persian 7.06 10.83 3.75 1.50 23.14

clover Oats 0.00 0.00 2.25 0.00 2.25 Senji 8.03 0.00 0.00 0.00 8.03 LSDo.o5 1.08 2.12 0.89 0.36 3.20

54 G. SINGH ETAL.

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