Relative growth performance of Latin American Prosopis species in the Indian arid tract - J.C. Tewari, N.K. Sharma and L.N. Harsh

Central Arid Zone Research Institute, Jodhpur 342003, India

Introduction

In the arid part of the Indian sub-continent, the fuelwood deficit is highly alarming, as the natural forest cover in the region has been depleted and is now almost negligible. The tree and shrub species found in the region are sparsely distributed and slow growing by nature. Therefore, a massive afforestation programme using fast growing tree species is urgently required in order to bring such lands back into productivity. P. juliflora has proved a suitable tree species for this region due to its very high degree of adaptability (Muthana and Arora, 1983). Farmers, however, dislike it due to the thorny nature of the species and because agricultural crops are adversely affected by the establishment of this species. Besides P. juliflora, there are 43 other species of the genus, some of which could prove useful in the afforestation of the arid zones, but until recently little work has been carried out on field testing these species. This paper presents the performance of six exotic Prosopis species and a naturalised local P. juliflora under arid field conditions.

Materials and methods

Seeds of six Prosopis species of Latin American origin; P. alba, P. chilensis, P. flexuosa, P. nigra, P. sp. ‘hybrid’ and P. sp. ‘Peru’ were provided by Texas A&M University, Kingsville, U.S.A. and were evaluated for their early growth at the Central Arid Zone Research Institute, Jodhpur. The growth performance of these exotics was compared with local P. juliflora. Seeds of all species were sown in nursery in polythene tubes, containing a 1:1:2 ratio of farm yard manure, soil and sand, in March 1991. Five months later, seedlings were out-planted in the field, at a 2.5 x 4 m spacing in a randomised block design with four replications. Plants were watered (15 l/plant) fortnightly in the summer and once a month in the winter during the first year after planting. Weeding was carried out twice a year for the first 3 years. Data were recorded for survival, plant height, collar diameter and crown diameter and analysed using Duncan’s multiple range test (Gomez and Gomez, 1983).

Results and discussion

Survival percentage of all species is presented in Table 1 and results showed that after 3 years, maximum survival was recorded for P. nigra (90.25%) with the lowest recorded for P. flexuosa (66.41%), all other species having between 70-82% survival. Almost all the mortalities occurred within the first year, with no further losses recorded for any species between years 2 and 3. Means of plant height and collar diameter recorded over the first 3 years and that of crown diameter at the end of the third year only, for all species are given in Table 2. After the first and second growing season, P. sp. ‘Peru’ had a significantly higher maximum mean plant height (89 cm and 160 cm respectively) and although still the highest in the third year, no significant differences were found between P. sp. ‘Peru’, P. alba, P. chilensis and P. sp. ‘hybrid’. After 1 years growth, P. juliflora was significantly the poorest in respect of plant height, but then it almost doubled its height in each of the two following years, showing that even the naturalised P. juliflora exhibited signs of slow establishment. P. nigra was significantly the poorest species in terms of plant height in the second and third years.

Table 1. Survival percentage of 7 Prosopis species over 3 years

Table 2. Mean height, collar diameter and crown diameter of 7 Prosopis species over three years, ranked in order of plant height after 3 years. Means in the same column followed by the same letter are not significant at the p=0.05 level.

Similar trends were noted with collar diameters, with the poor early performance of P. juliflora increasing rapidly over the 3 years. P. nigra was significantly smaller after 3 years than all species except P. flexousa. Comparable crown diameters after 3 years were observed however, the only significant differences existing between P. sp. ‘Peru’ (328 cm) and P. flexousa (261 cm). From the data collected and analysed for early growth of introduced exotic Prosopis species, it was discernible that all are adapted to the environmental conditions of the hot Indian arid tract. Overall, the performance of P. sp. ‘Peru’ was seen as superior, closely followed by P. alba and P. chilensis. Few significant differences were recorded for the growth parameters of the naturalised P. juliflora and most of the exotic species tested, only P. sp. ‘Peru’ being larger after 3 years and P. nigra smaller, in terms of height and collar diameter. Moreover, the thorny nature of P. juliflora is a constraint for the non-adoption of this species by the rural population and for plantation forestry and agroforestry programmes, while some exotic Prosopis species, P. sp. ‘Peru’ and P. alba for example, are generally thornless and as such could be successfully introduced in the place of P. juliflora, and better accepted by local farmers.

Acknowledgements

The financial grant from the Indo-US, PL-480 project, grant no. FG-IN-749 is gratefully acknowledged.

References

NAS (national Academy of Sciences), 1980. Firewood crops: shrubs and tree species for energy plantation. National Academy of Sciences, Washington D.C. 273p.

Gomez, K.A. and A.A. Gomez, 1983. Statistical Procedures for Agricultural Research. Wiley Interscience Publication, Jon Wiley & Sons, New York.

Muthana, K.D. and G.D. Arora, 1983. Prosopis juliflora (Swartz) DC, A fast growing tree to bloom the desert. CAZRI Monograph No. 22. Central Arid Zone Research Institute, Jodhpur, India. 19p.