INTEGRATED SALINE WATER MANAGEMENT IN MAIZE (ZEA MAYS L.) FODDER PRODUCTION

Abstract

The scarcity of good quality irrigation water is a severe problem in dry areas of Pakistan, which has forced growers to widely explore the possibility of using salty water for irrigation. The shortage of irrigation water has increased since last decade, it is incumbent on agriculture to maximize the use of water of all qualities. Irrigating crops in presence of saline groundwater presents unique opportunities and challenges. Some studies reported that use of saline water for irrigation is feasible, especially when saline water is blended or alternated with good quality water. A series of experiments was conducted in laboratory, glass-house and field conditions at Sindh Agriculture University, Tandojam and Universiti Putra Malaysia from 2004 to 2007. Ten maize cultivars (Hicorn, Agaiti-2002, Margalla, Akbar, Sahiwal 2002, EV-5098, EV-3001, EV-1098, EV-6098 and EV-4001) were screened for salt- tolerance under different water qualities (EC 0.4, 2, 4, 6 and 8 dS m-1). Four maize cultivars were selected (EV-1098 and Agaiti-2002 as salt-tolerant and EV-4001 and Akbar as most salt-sensitive) and were further tested under saline irrigation scheduling and farmyard manure levels. The cultivar screening studies showed that out of ten maize cultivars, EV-1098 and Agaiti-2002 were salt-tolerant and EV-4001 Akbar were most salt- sensitive. It was observed that increase in salinity of water from EC 2.0 to 8.0 dS m-1 significantly affected all agronomic traits as well as soil and plant chemical properties. Maximum plumule, radical length, plumule, radical fresh weight, plumule, radical dry weight, plant height, stem girth, green leaves plant-1, green fodder and dry fodder yield were found under application of canal water (EC 0.40 dS m-1) and water quality having EC 2.0 dS m-1. Both treatments were at par with each other. It was further observed that application of saline water beyond EC 2.0 dS m-1 significantly reduced all the plant parameters and minimum values were exhibited under EC 8.0 dS m-1. Results indicated that soil salinity increased with increasing salinity levels of irrigation water. Same trend was observed in case of soluble cations (Na+, Ca2+, and Mg2+), anions (Cl- and SO42-), sodium adsorption ratio and exchangeable sodium percentage. However, soluble K+ decreased in soil profile with increase in water salinity. Over all results further indicated an increased contents of EC, soluble cations (Na+, K+, Ca2+ and Mg2+), soluble anions (HCO3-, Cl-, and SO42-), SAR and ESP at surface soil layer compared to lower layers, however, pH was more in lower soil depths. Among the cultivars, EV-1098 and Agaiti-2002 had good performance containing lower concentrations of Na+ and Cl- and higher K+, Ca2+ and Mg2+, resulting in higher K+/ Na+ ratio. The cultivar EV-4001 and Akbar accumulated maximum concentration of Na+ and Cl- and minimum concentration of K+, Ca2+ and Mg2+ and were identified as salt-sensitive. A pot study on saline irrigation scheduling showed that application of canal water (EC 0.18 dS m-1) at all growth stages of maize and treatments comprising canal water application during soaking and at early whorl stage and saline water (EC 4.0 dS m-1) during late whorl stage were at par with each other and produced taller plants, maximum stem girth and green leaves plant-1, green and dry fodder yield. In contrast, these plant traits decreased in the treatments where sole application of saline water was applied at all growth stages. In this irrigation scheduling study,EV-1098 and Agaiti-2002 were salt-tolerant with better performance compared to EV-4001 and Akbar as salt-sensitive. The values of EC, soluble Na+, Cl-, SO42-, SAR and ESP in soil increased where crop received saline water throughout growing period. The soluble K+, Ca2+ and Mg2+ contents in soil increased where canal water was applied from sowing to harvest. FYM reduced the negative impact of saline water on crop parameters including fodder yield. Maximum response was obtained at FYM 25 tons ha-1, beyond this non-significant increase in the agronomic values was noted. Sole application of saline water reduced the growth and fodder yield of maize cultivars and increased salt contents in soil and caused accumulation of toxic ions (Na+ and Cl-) in plant. The salt-tolerant cultivars (EV-1098 and Agaiti-2002) responded better under saline condition compared to salt-sensitive (EV-4001 and Akbar) cultivars by maintaining more concentration of K+, Ca2+ and Mg2+ in plants. Regression analyses across maize cultivars, water qualities, irrigation scheduling and FYM showed positive relationships of plant height, green leaves, and K+ concentration in plant and negative relationship of dry leaves, Na+ and Cl- accumulation in plant with maize fodder yield. The unit increase in various traits resulted in corresponding increase in maize green fodder yield. It was concluded that EV-1098 and Agaiti-2002 were most salt-tolerant cultivars and EV-4001 and Akbar were more salt-sensitive against saline irrigation water. Canal water application to maize and canal water application during soaking + early whorl stage + brackish water (EC 4.0 dS m-1) during late whorl stage were equally efficient where lower accumulation of toxic ions in plants were noted. The saline water could also be applied to maize at later growth stages when canal water is scarce. The adverse effects of the saline water could also be minimized by the application of canal water or incorporation of FYM at the rate of 25-30 tons ha-1 in the soil.