Abstract: In order to study the effect of various salinity levels on the yield and yield components of Pearl millet, a pot experiment was conducted at NWFP Agricultural University Peshawar, Pakistan during 1998. The performance of various millet varieties evaluated was significantly different for germination %age, leaf area, plant height, total biomass and grain yield plant–1. Genotype ICMV-94151 was found to have maximum leaf area, plant height, biomass and grain yield plant–1 both at 15 and 30 days after salt application. Three millet varieties ICMV-941 51, ICMV-95490 and Gana white performed better than the others. Increasing salinity levels had significantly reduced germination percentage, leaf area, Plant height, total biomass and grain yield plant–1.
Introduction
Due to a number of problems, the production from the total cultivated area of Pakistan does not match with the production of other developing countries. These problems include inadequate drainage, water application, shortage of fertilizer, water logging and salinity. Among these problems salinity plays a very important role in the agricultural system of Pakistan. Salinity have a very bad effect on plant life, residential buildings and general hygienic conditions. Poor physical conditions of soil, death of microbes, restricted root growth and poor decomposition of organic matter, all are caused by salinity. Keeping in view the key role of salinity in the agrarian economy of Pakistan, the present project was designed to screen different millet varieties for their salinity tolerance. Onkware and Ochieng (1993) reported that seed germination, plant height and leaf area decreased with increasing salinity levels. Salinity reduced specific leaf area which indicates alteration in leaf expansion and carbon allocation (Cramer et al., 1994). Yield and yield related traits of different pear millet varieties progressively decreased with increased salinity (Nisha et al., 1993; Guandalia et al., 1992; Kumawat et al., 1991; Alam and Naqvr, 1991).
Materials and Methods
A pot experiment was conducted at NWFP Agricultural University Peshawar Pakistan during 1997 to study the effect of different salinity levels on various varieties of Pear millet. The experiment was laid out in Completely randomized design (CRD) with three replications. Each pot (30×35 cm) was filled with 20 kg of soil. The seeds were sown at uniform depth (2 cm) and after completion of emergence, thinning was done and seven plants were maintained in each pot. Recommended dose of commercial fertilizer at the rate of 100-50-0 NPK kg ha–1 was applied to each plot. The amount of fertilizer required for each pot was calculated by the following formula Fertilizer required = Nutrient ha–1 X weight of soil in pot Soil weight ha–1 (20,00,000 kg) Eight varieties of millet (Gick-93771, ICMV-95490, ICMV-9451, Bari-MS-22-95, BS-2, Gana white, Togo and V-94-1 were subjected to different salinity levels (0, 4, 8, 12 and 16 dS m–1) through irrigation water by addition of salt in increments 30 days after emergence. Data regarding leaf area and plant height was recorded at 15 and 30 days after salt application while days to maturity, total biomass and grain yield. plant–1 data was collected at maturity. To record data concerning germination percentage, a separate experiment was carried out by exposing the seeds to salinity levels through irrigation water before sowing.
Results and Discussion
Data regarding germination is presented in Table 1. Statistical analysis of the data revealed that various varieties, different salinity levels and their interaction had a significant (p<0.05) effect on germination. Mean values of the data showed that maximum germination of 71.80% was recorded for ICMV95490 which was at par with the genotype ICMV- 94151 (70.87%). While Gick-93771 recorded minimum germination (61.40%). Data regarding different salinity levels showed that germination was progressively reduced with increasing salinity levels. Maximum reduction was observed when plants were exposed to high salinity levels (i.e. 16 dS m–1). Similarly, data concerning varieties and salinity levels interaction showed that maximum germination was noted for ICMV- 95490 when grown at control while minimum germination was observed for Gick-93771 when exposed to salinity levels of 16 dS m–1. This difference in germination might be due to the physical damage caused by addition of salt on the emerging radicle and plumule and the inherent genetic capabilities of the varieties. Similarly, salinity causes water stress which resulted in low water absorption by seeds required for various enzymatic activities during germination. In addition, ions like Na or CI are toxic, if absorbed in higher concentration which may reduce germination in moderately salt tolerant crops like millet. Similar results are also reported by Bernal et al. (1974), Ahmad et al. (1981), Kingsbury and Epstein (1984), Rashid (1986) and Due (1989). Data recording leaf area was recorded at two growth stages. i.e., 15 and 30 days after salt application. Analysis of leaf area showed that varieties and salinity levels had significantly (p<0.05) affected leaf area both at 15 and 30 days after salt application, Whereas interaction was non significant (Table 2). Mean values of the data revealed that ICMV-94151 attained maximum leaf area (137 and 199 cm2) at both growth stages while minimum leaf area was noted for Gick-93771 and Togo at 15 and 30 days after application respectively. Plants subjected to high salinity (i.e. 16 dS m–1 attained minimum leaf area while plants grown at control recorded maximum leaf area at both growth period. Similarly, ICMV-94151 when grown at control produced maximum leaf area while Gick-93771 recorded minimum leaf area when exposed to high salinity levels both at 15 and 30 days after salt application.
| Table 1: | Germination percentage of various millet varieties as affected by different salinity levels |
| LSD(0.05) values for varieties = 3.602 = LSD(0.05) values for = 2.848 =LSD(0.05) values for 8.035 | |
| Table 2: | Leaf area {cm)2 of various millet varieties at different days after salt application |
| Table 3: | Plant height (cm)2 of various millet varieties at different days after salt application |
The difference in leaf size might be due to higher salt concentration added to the soil and the inborn genetic capabilities of different varieties. Increase in salt concentration in the soil had an adverse effect on the osmotic exchange between root hairs and soil solution and the plants were unable to absorb water from the soil, thus making the soil physiologically dry. Increased salt accumulation had a negative effect on the availability of certain nutrients particularly nitrogen to the plants (Bernal et al., 1974; Kawasaki et al., 1983). The plants are thus unable to develop maximum leaf area due to water and nutrient stress caused by salinity. The toxic effect of Na+ at higher salinity levels might also be responsible for decrease in leaf area production. Kumawat et al. (1991) reported a decrease in leaf area with an increase in salt application.
| Table 4: | Days to maturity of various millet varieties as affected by different salinity levels |
| Table 5: | Total biomass (g/plant) of various millet varieties as affected by different salinity levels |
| LSD(0.05) values for varieties = 0.9949 = LSD(0.05) values for = 0.7865 =LSD(0.05) values for 2.225 | |
| Table 6: | Grain yield (g/plant) of various millet varieties as affected by different salinity levels |
Table 3 indicates data regarding plant height recorded at 15 and 30 days after salt application. Statistical analysis of the data revealed that varieties and salinity levels had a significant (p<0.05) effect on plant height at both growth periods. Mean values of the data showed that ICMV-94151 attained maximum plant height 166.62 and 99.59 cm) while dwarf plants (56.68 and 90.22 cm) were noted from Togo at both growth periods. i.e. 15 and 30 days after salt application. It can be also inferred from the data that plants exposed to high salinity level (16 dS m–1) produced dwarf plants while taller plants were noted at control at both 15 and 30 days after salt application. Similarly, ICMV-94151 when grown at control produced taller plants whereas Togo when subjected to high salinity level recorded dwarf plants. It was noticed that increasing salinity levels had progressively decreased plant height which may be due to decrease in leaf area because of Na toxicity. Water and nutrient stress (Bernal et al., 1974; Kawasaki et al. (1983). The decrease in leaf area might have resulted in decrease in photosynthates production which in turn reduced plant height. Increasing salinity levels had significantly decreased plant height. Alam and Naqvr (1991), Kingsbury and Epstein (1984), Zahid et al. (1986), Singh and Rana (1987), Sharma and Swarup, (1988) Data recording days to maturity is presented in Table 4. Analysis of the data revealed that days to maturity were non significantly affected by varieties, salinity and their interaction. However, mean values of the data indicated that V-94-1 took more days to maturity whereas ICMV-94151 took minimum days to maturity. Similarly, Togo when exposed to 12 dS m–1 matured later whereas the same variety at control took minimum days to maturity.
Table 5 presents data regarding total biomass. plant–1 at harvest. Statistical analysis of the data indicated that biomass was significantly (p<0.051 affected by varieties, salinity levels and their interaction. It can be seen from the data that ICMV-94151 produced maximum biomass. plant–1 (43.13 g) while minimum biomass plant–1 (36.08 g) was recorded from Togo. Mean values of the data regarding salinity levels showed that biornass was minimum (22.98 g Plant–1) when plants were exposed to high salinity level (16 dS m–1) while plants grown at control recorded maximum biomass (49.34 g plant–1) . Similarly, it is also clear from the data that ICMV-94151 when grown at control produced maximum biomass. plant–1 while Togo when exposed to high salinity (16 dS m–1) recorded minimum biomass plant–1. Improper development of leaves due to salt stress might be responsible for decrease in biomass production. Similar results are also reported by Guandalia et al. (1992).
Data recording grain yield plant–1 is shown in Table 6. Statistical analysis of the data revealed that varieties, salinity levels and their interaction had a significant (p<0.051 effect on grain yield. plant–1. Mean values of the data indicated that ICMV-94151 produced maximum grain yield of 9.21 g plant–1 while Togo recorded grain yield of 8.89 g plant–1. It can be also seen from the data shown in Table 6, that grain yield. plant–1 progressively decreased with increase in salinity level, maximum reduction in yield was observed at 16 dS m–1 while plants grown at control produced maximum grain yield plant–1 (11.87 g). Mean values also indicated that ICMV-94151 when grown at control produced maximum grain yield plant–1 whereas Togo when subjected to high salinity level recorded minimum grain yield plant–1. This decrease in grain yield by salinity may be due to lower leaf area development as result of sodium toxicity, water and nutrient stress which in turn reduced net assimilates. These results are substantiated by Nisha et al. (1993), Kumawat et al. (1991), Zahid et al. (1986), Francois et al. (1998) and Verma and Neue (1984), who reported a decrease in grain yield due to addition of salts.