SAXENA AND GUPTA
LITCHI IN RECLAIMED ALKALI SOILS
Indian Journal of Agricultural Sciences
Effect of soil pH on the establishment of litchi (Litchi chinensis Sonn.) plants in an alkali environment*
C K SAXENA1 and S K GUPTA2
Central Soil Salinity Research Institute, Karnal 132001
Received: 5 July 2005
Key words: Litchi, alkali soils, soil pH, initial establishment, height, girth
A switch over from arable to horticultural crops could ensure nutritional security, help to conserve natural resources and boost export through value addition. Most of the reclaimed alkali lands under rice-wheat system assessed at around 1.3 million ha provide an opportunity to achieve this objective. As the reclamation process of alkali lands proceeds over the years, questions about the suitability of these lands for salt sensitive horticultural crops are being addressed to the research organizations. A number of horticultural crops such as guava, pomegranate, aonla (Phyllanthus emblica) and others varying in their salt tolerance have been tested in the past using different establishment techniques (Singh et al. 1998, Dagar et al. 2001). Initial establishment and long-term performance of the salt sensitive crop such as litchi has so far not been tried in reclaimed alkali soils. Litchi, currently cultivated in an area of about 56.4 thousand ha with a total production of 433.2 thousand tones (Singhal 2003), is known to grow well in wide variety of soils with pH in the range of 5.5 – 6.5 (Maity and Mitra 2002). Since litchi has high nutritional value and export potential, information on the level of soil pH for successful cultivation of litchi in reclaimed alkali lands could help to diversify arable cropping on these lands. This paper attempts to test the performance of litchi plants on reclaimed alkali lands under varying pH environment.
The present study was initiated at the farm of Central Soil Salinity Research Institute, Karnal during 2002-04 in a field of 90 m x 48 m size. This plot was a part of the barren alkali land in 1969 with pH2 in the range of 10.2 – 10.5. The soil (Aquic Natrustalf) is sandy loam to loam in texture at the surface (0-15 cm) and loam to clay loam in lower layers. This area was reclaimed by differential doses of gypsum to create plots having different pH and to use these test plots to study the effect of varying pH on cereal and vegetable crops. Adjoining land was also reclaimed at various times during the intervening period. With the addition of gypsum and continuous rice-wheat cropping in the adjoining area, the pH2 of the soil decreased to 7.5 to 9.0 in the 0-15 cm layer during November 2000. Exchangeable sodium percentage (ESP) of the soils also came down from more than 90 to 15-45 in the top layer. However, both the pH and ESP increased with increasing depth. Wide spatial variation in pH and ESP could be observed in the plot. As such, this plot offered an opportunity to study the initial establishment of litchi plants under different pH environment.
A total of 130 ‘Rose Scented’ litchi plants were planted in November 2000. The plants were established in pits of 30 cm x 30 cm x 30 cm size. These pits were back-filled with original soil mixed with 20 kg of sand and 20 kg of farm yard manure at plant to row spacing of 4.25 m x 6.25 m. In order to minimize the labour requirement for irrigation as well as to apply water uniformly to all the plants, drip irrigation was superimposed in 2001. Soil samples were drawn within 30 cm radius from all plants at the depth range of 0-150 cm in increments of 30 cm each. The soil pH2 was determined in 1:2 soil:distilled water suspension. Since the plants were established at or around 15 cm depth in the pits, soil pH2 of the top surface layer (0-30 cm) did not play a significant role. Thus, the weighted average of soil pH2 for 30-150 cm depth was determined to have a representative value of the soil pH2 for all plant locations. There were 49, 29 and 46 plants respectively in the soil pH2 levels of less than 8.0, 8.0 to 8.5 and above 8.5, which were considered as treatments in the study.
The plant height was measured from the ground to the highest point of the crown by wooden scale and/or measuring tape. The girth at collar was computed from the mean diameter of the stem measured at 5-10 cm above the ground by vernier caliper. The arithmetic average as well as the range at 95% confidence level around the median of these parameters under different pH groups was determined. The growth parameters of plant height and girth at collar were statistically analyzed by using ‘F’ test as per one-way classification (Cochran and Cox 1977).
Root sampling was carried out at 0-15, 15-30 and 30-45 cm depths from representative plants under different pH groups using core sampling technique during March 2004 (Schuurman and Goedewaagen 1971). The average dried root weight from different distances and directions was transformed into the root weight for the entire soil volume of 60 cm radius around the plant.
The response of plants in terms of height and girth at collar as affected by the pH is shown in Table 1. The average plant height and the girth at collar are high at low pH2 and a clear decreasing trend in the height and girth with increasing pH2 is evident (Table 1). The percent mortality among the plants at pH2 level up to 8.5 was low as compared to the environment where the pH2 was more than 8.5. The mortality during the experimental period was 2.0, 0 and 9.8% respectively at three pH2 levels of less than 8, 8-8.5 and above 8.5. The difference in height and girth among groups could have been more if mortal plants were not discarded. The statistical analysis revealed that the plant height is significantly different among three pH levels at 9.42, 1 x 10-3 and 5 x 10-8 % probability levels in the years 2002, 2003 and 2004 respectively. Clearly, the high probability in 2002 reveal that plant population could be treated as uniform at the initiation of the experiment in the year 2002. However, it is clear that the level of significance increased among three pH levels over the years as the plant aged 2.5 and 3.5 years respectively in June 2003 and 2004. A similar trend was seen in the case of plant girth at collar. The percentage increase over the year 2002 in height was 59.9 and 155.1% in 2003 and 2004, while for the girth at collar it was 93.1 and 171.3% respectively during the same period at pH2 level of less than 8.0 (Table 1). There was a downtrend in the percentage increase in height and girth at collar although difference in height at the pH2 range 8.0 – 8.5 and more than 8.5 are not much. But the differences are quite visible in the percentage increase in girth at collar at these two levels of pH (Table 1).
Average root weight from the soil mass of 60 cm radius around the plant in the 0-15, 15-30 and 30-45 cm profile revealed that the highest root weight at all the depths occurred in treatment where pH level was less than 8.0 compared to the other pH levels (Table 2). The plants under the pH levels of more than 8.5 have shown tremendous reduction in the root weight compared to the plants under pH 8.0 or 8.0 to 8.5. Thus, when the plant height, the girth at collar and the root weight are seen together, it is clear that performance of litchi plants is adversely affected at pH2 above 8.5 and mildly affected at pH between 8.0 – 8.5 compared to a pH level of 8.0 or less. It is also noticed that differences between height and girth are increasing over the years with increasing pH levels. Thus, it is apparent that for sensitive plants, spot reclamation of alkali lands might not be helpful in the long-term establishment of the plants since plants would experience the salt stress at later growth stages. Thus, it could be concluded that diversification of reclaimed lands from arable cropping (rice-wheat) to plantation of litchi, a relatively salt sensitive plant, should be initiated before the lapse of 10-12 years following land reclamation when the pH2 would come down to 8.5 or less (Abrol et al. 1988).
The performance of litchi plants at the initial establishment stage was found to be the best at soil pH2 less than 8.0, followed by pH2 between 8.0-8.5 and above 8.5. Since there is a drastic reduction in the performance above pH2 8.5, it could be concluded that plantation of litchi could be considered only when the pH2 of the reclaimed lands has come down to a level below 8.5. It is also concluded that sensitive plants like litchi should not be grown with spot reclamation of lands rather the lands reclaimed for arable cropping should be used for diversification to such plantations after 10-12 years of arable cropping.
REFERENCES
Abrol I P, Yadav, JSP and Massoud, F I. 1988. Salt affected soils and their management, 131 pp. FAO Soil Bulletin No.39. Food and Agriculture Organization of the United Nations, Rome.
Cochran W G and Cox M C. 1977. Experimental Designs, 611 pp. Second Edition. Asia Publishing House, Bombay, Maharashtra, India.
Dagar J C, Singh G and Singh N T. 2001. Evaluation of forest and fruit trees used for rehabilitation of semiarid alkali-sodic soils in India. Arid land research and management 15(2) : 115-33.
Maity S C and Mitra S K. 2002. Litchi (in) Fruits: Tropical and Sub-tropical. pp 556 –608 Vol. I. Bose, T K, Mitra, S K and Sanyal, D. (eds). Naya Udyog, Bidhan Sarni, Kolkata.
Schuurman J J and Goedewaagen M A J. 1971. Methods for the examination of root systems and roots, 86 pp. Centre for Agricultural publishing and Documentation. Wageningen.
Singh G, Bhist J K, Singh N T, Dagar J C and Singh G. 1998. Evaluation of fruit plants for sodicity tolerance. Range management and agroforestry 19(1) : 87-91.
Singhal V. 2003. Indian Agriculture 2003, 799 pp. Indian Economic Data Research Centre, New Delhi, India.
Table 1 Effect of soil pH on plant height, girth and annual increase in these parameters
Range 95% / Average / Annual
increase
(%) / Range 95% / Average / Annual
increase
(%)
Min / Max / Min / Max
Jun 2002
< 8.0 / 56.58 / 71.42 / 65.69 / - / 43.17 / 52.33 / 47.94 / -
8.0-8.5 / 63.04 / 76.96 / 71.49 / - / 39.25 / 49.35 / 47.84 / -
> 8.5 / 56.56 / 65.94 / 60.70 / - / 39.62 / 45.20 / 41.31 / -
SEm + / 1.89 / 1.21
P-Value / 0.0942 / 0.0303
Jun 2003
< 8.0 / 93.91 / 112.09 / 105.04 / 59.89 / 78.27 / 96.33 / 87.79 / 83.13
8.0-8.5 / 83.32 / 102.68 / 99.79 / 39.58 / 56.83 / 75.77 / 75.68 / 58.20
> 8.5 / 74.74 / 85.26 / 79.30 / 30.66 / 57.05 / 66.05 / 63.58 / 53.89
SEm + / 2.52 / 2.42
P-Value / 1x 10-05 / 3 x 10-05
Jun 2004
< 8.0 / 160.79 / 183.21 / 167.59 / 59.55 / 115.56 / 139.44 / 130.05 / 48.14
8.0-8.5 / 120.64 / 145.36 / 143.60 / 43.90 / 86.65 / 113.75 / 110.56 / 46.09
> 8.5 / 120.14 / 136.86 / 118.00 / 48.79 / 84.22 / 97.68 / 88.14 / 38.64
SEm + / 3.59 / 3.47
P-Value / 6 x 10-10 / 2 x 10-07
Table 2 Root weight (g) within 60 cm radius of plant
pH level / Depth (cm)0-15 / 15-30 / 30-45
< 8.0 / 154.97 / 217.59 / 163.60
8.0-8.5 / 132.73 / 85.51 / 74.36
> 8.5 / 70.56 / 32.93 / 18.81