Effect of saline irrigation and its schedules on growth, biomass production and water use byAcacia niloticaandDalbergia sissooin a highly calcareous soil

Abstract

Afforestation programmes in arid areas suffer mainly from low rainfall, high evapo-transpirational demands, high salt content of ground-waters and impediment bykankar(calcareous) subsoil layers of root proliferation. Two of the most preferred multi-purpose tree (MPT) species, Kikar (Acacia nilotica(L.) Del.) and Shisham (Dalbergia sissooRoxb. ex DC) were furrow planted in August 1991 under such an environment in north-western parts of India and the effects of saline irrigation (ECw10·5 dS m−1, sodium adsorption ratio 20 mmol l−1) and various irrigation schedules were evaluated for 45 months. Saline irrigation reduced biomass by 16% inA. niloticacompared to canal water irrigation, while the reduction was 57% inD. sissoo. Irrigation water supplies equalling 10% of the open pan evaporation (OPE) values met water requirements during the initial 2 years after transplanting. However, trees receiving high quantities of water (20% of OPE) during the third year had improved biomass yields by 13% and 21% inD. sissooandA. nilotica, respectively. Water-use efficiency (WUE) ofA. nilotica(10·7 mg.ha.m−1) was much higher compared toD. sissoo(1·7 mg.ha.m−1). Most of the salts added through saline irrigation accumulated below channels and were leached both downward and to lateral regions with monsoon rains. Thus furrow planting and irrigation technique, in addition to reducing the applied water quantities, resulted in favourable salt and water regimes for the better establishment of tree saplings with saline water.