Hant and Soil 87,329-335 (1985). 9 1985 Martinus NifhoffPublishers, Dordrecht. Printed in the Netherlands.

Ms. 5934

P e r f o r m a n c e o f s o m e forest tree species in saline soils u n d e r shallow and saline water-table c o n d i t i o n s O. S. TOMAR and R. K. GUPTA

Central Soil Salinity Research Institute, Karnal-132001, India Received 24 May 1984. Accepted February 1985

Key words Planting methods Salinity Survival percentage Tolerance Trees Water table Summary Field studies were carried out to study the influence of seasonal variations in salinity and soil moisture profiles due to fluctuating water table on the performance of 16 tree species. Over a yearly cycle water table having an EC of 2 - 4 6 mmhos/cm fluctuated between 10-140 cm from the surface. Seasonal variation in salinity profiles indicated that subsurface planting (30 cm below surface) provides less hostile saline environment to the roots. Due to genetic differences, species of trees differed in their ability to withstand salinity and aeration stresses individually and simultaneously. In areas where salinity is not associated with high water table conditions, tree species like Acacia auriculiformis, Terminalia arjuna and Leucaena leucocephala can be grown. Tree species like Casuarina equisetifolia Tamarix articulata and Prosopis juliflora can be planted where high salinity or high water table conditions exist separately or simultaneously. If planting occurs on ridges, Acacia aurieuliformis, Acacia nilotica and Terminalia arjuna can also be grown in these conditions.

Introduction The ever growing food and energy requirements make necessary the utilization of salt affected soils, previously abandoned because of the detrimental effects associated with salinity. Reclamation of saline soils require adequate provisions of low electrolyte irrigation water and drainage to handle the leachate. In absence of mandatory drainage facility, all efforts to keep these lands under cultivation have met with frustration. Of recent, efforts are being made to utilize such lands for creating forest raw material resources. The likelihood of success of revegetation programme depends on the kind, content and distribution of salts in the soil profile and moisture regimes prevailing particularly during the critical period of plant growth. It is during this period that the plants are more sensitive to unfavourable salinity conditions and may become resistant in other growth stages2,1~ Because of this phenomenon and the complex interactive effects of salinity and poor aeration, operative simultaneously under high water table conditions, it is often difficult to establish a scale of salt tolerance. Due to lack of a reliable scale for salt tolerance, it seems more relevant to seek the critical period in the early vegetative development phase 329

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of the hard woody perennial species of trees. The survival and growth of saplings during the critical period may however, be manipulated through changes in land configuration and other suitable agronomic practices to provide less hostile saline environment to roots. The present investigations were carried out to study the influence of seasonal variations in salinity and soil moisture profiles due to fluctuating water table on survival of some species of trees. Materials and methods Seasonal variations in salt and moisture profiles and fluctuations in water table (period 1982-1983) were studied in a microplot established at experiment station Sampla of the Central Soil Salinity Research Institute, Karnal (Haryana). The farm soils are sandy loam in texture and contain excess of chloride, sulphate salts of Ca, Mg and Na. The area has a semi-arid climate with a mean annual precipitation of 650 mm, of which nearly 80 percent is received during July to September. The average monthly temperature varies from 21~ in January to 40.5~ in May. Ground water samples from the piezometric tubes were collected periodically. Soil samples were collected at 15 cm depth interval upto water table for salinity and soil moisture determinations. Soil and water samples were analysed for their chemical composition. Bulk density of the different soil layers were determined using a 10 cm diameter, 15 cm long core sampler. Porosity of the soil was calculated using bulk density data of the different layers.

Field studies A field experiment to study the survival of 16 tree species was initiated in July, 1982. Tree species studied for their survival under field conditions are given in Table 1. Six month old saplings of the tree species raised in i kg capacity polyethylene bags, were transplanted by two method: 1) subsurface and 2) ridge planting. The row to row and plant to plant spacings were 3 and 2 meters respectively. The saplings were transplanted in pits (30 cm diameter) dug out upto a depth of 45 cm with a tractor driven auger. Saplings were placed in pits at a depth of 30 cm from the surface. From the pits, soil samples (30-45 cm depth) were collected before and after irrigation for determining the range of salinity in the rhizosphere. Earthen rings were provided around each sapling for ponding irrigation water by buckets when required. Saplings were also transplanted on the ridges prepared in July, 1982. The ridges were 1.6, 3.0 and 4.5 m wide at the top, middle and bottom respectively. The height of the ridge from the original surface was kept at 45 em. Since water table rises close to soil surface, the ridges were designed to reduce salinisation and facilitate soil aeration rather than store rain water in the trenches. Earlier working under similar conditions, it was reported that the critical depth of water table for the soil to be free of salts is about 80 cm below the zone of root influence9. Saplings were transplanted in staggered double rows on the ridge tops, 30cm away from the edges. Small peripheral earthen rings were constructed at the edges of beds at ridge tops to facilitate leaching during rains. For salinity appraisal samples were collected for the ridge top surface (0-15 cm depth) before and after irrigations. Survival of plants was monitored after five months of transplantating. Forty eight saplings of each of the tree species in three replicates were planted by the two methods.

Pot study Two bulk soil samples were collected, one from a nearby field provided with subsurface drainage system and the other from the undrained experimental site. Except the salinity differences, soil samples were presumed alike in their general properties. The electrical conductivity of the saturation paste extracts (ECe) of soil samples from drained and undrained plots were 2.0 and 26.0 mmhos/cm respectively. The two bulk soil samples were mixed in such

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Table 1. Soil salinity and sapling survival percentage under subsurface and ridge planting methods

Tree species Acacia auriculiformis Acacia catechu A c a c i a nilotica Albizia lebbeck Cassia siamea Casuarina e q u i s e t i f o l i a Dalbergia sissoo Eucalyptus hybrid L e u caena l e u c o c e p h a l a Melia azedarach P a r k i n s o n i a aculeata Pongamia pinnata P r o s o p i s ]ulifolora Pyllanthus emblica T a m a r i x articulata T e r m i n a l i a ariuna

Salinity (mmhos/cm)

Survival (%)

Subsurface

Ridge

Subsurface

Ridge

6 - 15

11.20

63

85

6 - 15

8-10

0

21

10-14 * 3- 6 14 - 17

17 25 0 69

71

12 - 18

8-10

0

6

6-17

4-10

0

12-20 8-15 6-15 20-28

13 - 21 7- 8

* *

13 - 2 0 12 - 19 13 - 14

12-18 16-27 7 - 17

50 88 0

38 15

* *

6 - 16

25

44

9 - 16

13 23

* 71

8-12

0 81

50 *

7 - 10

13

71

*

*

* Tree species not tested on ridges. C.D. at 5% probability level (i) between tree species (ii) planting methods Off) species • methods were 9, 4 and 12 respectively.

proportions as to prepare two more soil lots of EC4 4.6 and 12.5 mmhos/cm. Thus, four bulk soils of ECe values 2, 4.6, 12.5 and 26 mmhos/cm were used for the pot experiment. Soils having ECe 2.0 and 12.5 mmhos/em were potted in 16kg capacity closed bottom plastic pots (45 cm height). Soils in pot were maintained at near field moisture capacity by periodical irrigations. The other two soils of ECe 4.6 and 26.0 mmhos/cm were filled in pots which were connected at the bottom with water bottles (40 cm in height, 1.5 litre capacity) to supply water to the piezometric tubes embedded in soil. Bottles were filled with water twice a day to keep the soils saturated with water. Since saturation moisture content (SP) is nearly twice of that observed at field moisture capacity (2 FC = SP), the solution salinity at field capacity (ECfe) will be twice the salinity measured in saturation paste extracts (ECe). Therefore, soils of salinity (ECe 2 and 12mmhos/cm) maintained at field moisture range will have approximately ECfe 4.6 and 26 mmhos/cm, respectively. Thus, ECfe 4.6 and 26 mmhos/cm (ECe 2 and 12.5) soils maintained at the field moisture content had no aeration problem. Soils of ECe 4.6 and 26 mmhos/cm had waterlogging/poor aeration problems. It is obvious from above description that there were two levels, each for salinity and moisture regimes in the pot study. Each treatment was replicated thrice. Survival of saplings under four different combinations of salinity and moisture were recorded after 40 days of transplanting the saplings.

Results and discussion With the onset o f monsoons there was a rapid rise in ground water table (Fig. 1) which remained very close to the surface during JulyAugust. Thereafter, the water table gradually decreased with occasional rises coinciding with rain. The minimum salinity o f ground water was observed during the monsoon (2 mmhos/cm). This was apparently due

332

TOMAR AND GUPTA 0

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90

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II

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17o

102 " 68

120 34

165

I

Aug 82

I

Oct

I

I Dec

1

I

t

I

Feb

Apt

I

1

Jun

I

I

;o Aug

Fig. 1. Seasonal changes in soil salinity and depth of ground water table at the experimental site.

EC, mmhos/cm 60

0

l

120

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Fig. 2. Salt distribution in the soil profile.

180 I

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SAPLING SURVIVAL IN SALINE SOILS

333

80

70

60

5o o

40

I Aug 82

I

I Oct

I

I Dec

I

I Feb 83

I

I Mar

i

I

May

Fig. 3. Water filled porosity of soil under original (solid circle) and ridge configurations.

to dilution effects. The maximum salinity ( 4 6 m m h o s / c m ) of the ground water occurred in the summer season (April-May). Observations show that salinisation continues from January through June. Salts accumulated in the surface ( 0 - 1 5 cm) layer and decreased with depth (Fig. 1). In periods of high evaporative demands, the zone of salt accumulation increased upto 30 cm depth (Fig. 2) and the lower layers appear to be in equilibrium with salinity of the ground water table. These observations are in conformity with earlier reports 7'8 Data in Fig. 3 indicate that more than 70 percent of the total porosity of surface soil layer ( 0 - 1 5 cm) remained filled with water during the greater part of the year. High water table condition and the presence of hygroscopic salts (chlorides of Ca, Mg) seems to be responsible for high moisture regimes. Depending on the level of salinity, soil samples gained upto 8 percent moisture from air on an oven dry basis. Salinity and moisture profile data clearly indicate that subsurface planting of saplings (below 30 cm depth) provides less hostile saline environment for the roots. Salinity and moisture contents were generally lower (Fig. 3, Table 1) in the ridges than the original land configuration. Ridge trench system thus help in avoiding/reducing salinity and aeration stresses.

Effect o f planting methods on plant survival Survival percentage of different plant species with subsurface and ridge planting methods are given in Table 1. In field, there was a great deal of spatial variability in the surface salinity, ECe values observed in the pits before and after irrigations have been reported in Table 1, at which saplings could survive. Compared with the ridge planting method, sapling survival rate with subsurface planting was generally low, Eucalyptus hybrid could not survive both with subsurface and

334

TOMAR AND GUPTA

Table 2. Effect of salinity and moisture regimes on the survival of saplings 40 days after transplanting in pots Salinity levels at Field moisture (ECfe)

Saturation moisture (ECe)

Tree species

4.6

26.0

4.6

26.0

Acacia auriculiformis Acacia ca techu Acacia nilotica Eucalyptus hybrid Cassia siamea Casuarina equisenfolia Prosopis ]uliflora Dalbergia sissoo Leucaena leucocephala Pongamia pinnata Terminalia arjuna

3 2 3 3 2 3 3 3 3 3 3

2 0 2 0 0 3 3 1 1 1 2

1 0 3 2 2 3 3 2 0 3 3

1 0 1 0 0 3 3 0 0 1 0

EC in mmhos/cm 1, 2 and 3 represents poor, moderate and good tolerance respectively. Complete mortality is '0'.

ridge planting methods. Cassia siamea and Dalbergia sissoo failed to survive with subsurface planting. However, tree species like Casuarina equisetifolia, Acacia auriculiformis, Tamarix articulata and Prosopis juliflora survived both high salinity and moisture regimes together, prevailing under subsurface planting. Delbergia sissoo and Parkinsonia aculeata had earlier been reported to survive saline water irrigations upto 1 7 m m h o s / c m 1'3'4 The low survival rates of these plant species in this study appears to be due to salinity being associated with high moisture regimes. Results of the pot study indicated that at salinity values (ECe 4.6 mmhos/cm), low survival of the species of trees like Leucaena leucocephala, Acacia auriculiformis, Acacia catechu, Cassia siarnea and Dalbergis sissoo was due to poor aeration. If salinity is not associated with waterlogging, Acacia auriculiformis, Acacia nilotica and T. arjuna can be grown upto a salinity of ECe = 26 mmhos/cm. Eucalyptus hybrid, Dalbergia sissoo and Cassia siamea could withstand poor aeration but failed to tolerate salinity (Table 2). Similarly, Acacia auriculiformis and Leucaena leucocephala can tolerate moderate salinity but are susceptible to poor soil aeration conditions. Prosopis ]uliflora and Casuarina equisetifolia seems to be highly tolerant, both to salinity and aeration stresses together. These observations of the pot study in general support our results from the field experiment. Acacia nilotica, Pongamia pinnata and Prosopis juliflora have been categorised

SAPLING SURVIVAL IN SALINE SOILS

335

as salinity tolerant tree species at the germination and the seedling stages 3'4'12 Casuarina equisetifolia, Tamarix articulata and Prosopis /uliflora are the c o m m o n phreatophytes for such areas 1~ Results show that in areas where salinity is associated with high water table conditions, Tamarix, Prosopis and Casuarina species can be subsurface planted with success. Acacia auriculiformis, Acacia nilotica and Terminalia ar/una can be grown in such areas if planted on the ridges. Keeping in view the tolerance of Casuarina species to alkalinity6/ salinity and waterlogging, it should find favour in the agro-forestry programmes for salt affected soils. References 1 2 3 4

5

6 7 8 9

10 11 12

13

Afar A 1975 Quality of water in relation to irrigation sandy soils. FAO Soils Bull. 25, 73-83. Ayers A D 1952 Seed germination as affected by soil moisture and salinity. Agron. J. 44, 8 2 - 8 4 . Bangash S H 1977 Salt tolerance of forest tree species as determined by germination of seeds at different levels. Pakistan J. For. 9 3 - 9 7 . Boyko H and Boyko E 1968 Plant growing with sea water and other saline waters in Israel and other countries. In Saline Irrigation for Agriculture and Forestry. Ed. H Boyko. Dr W Junk NV, The Hague, 8 5 - 9 2 . Firmin R 1968 Forestry trials with highly saline or sea water in Kuwait. In Saline Irrigation for Agriculture and Forestry. Ed. H Boyko. Dr W Junk NV, The Hague, 1 0 7 32. Gill H S and Abrol I P 1983 Casuarina a promising tree for sodic soils. Intensive Agriculture 21, 5 - 6 . Gupta R K and Khosla B K 1982 Seasonal variations in salt and water content profiles in shallow and saline ground water table. Indian J. agric. Sci. 5 2 , 5 0 6 - 5 1 0 . Jackson E A, Blackburn G and Clazke A R P 1956 Seasonal changes in soil salinity at Tintinare, South Australia. Aust. J. Agric. Res. 7, 20 -44. Khosla B K, Gupta R K and Chawla K L 1980 Evaluating the field hydraulic conductivity and soils salinization under conditions of high water table. Intern. Symp. Salt affected soils, Karnal 2 5 6 - 2 6 4 . Lopez G 1968 Germination capacity of seeds in saline soils. In Saline Irrigation for Agriculture and Forestry. Ed. H Boyko. Dr W Junk NV, The Hague. 11-23. Robinson T W 1958 Phreatophytes US Geol. Survey water supply Papers, 1423, 84 pp. Tomar O S and Yadav J S P 1980 Effect of saline irrigation water of varying EC, SAR and RSC levels on germination and seedling growth of some forest species. Indian J. For. 3, 306-314. Yadav J S P 1981 Soil limitations for successful establishment and growth of Casuarina plantations. Conference on Casuarina organized by C.S.I.R.O., Canberra, Australia 17-21 August.