Response of Wheat to Applied Supplemental Potassium in Saline Sodic Soil
Shahzada Munawar Mehdi,
Syed Adeel Akhtar Shah
A field experiment was conducted to determine the response of wheat to applied potassium in saline-sodic soils. Five rates of K2O were applied i.e., 0, 30, 60, 90 and 120 kg haG1 along with a basal dose of N and P2O5 i.e., 140 and 110 kg haG1, respectively. The whole of P, K and 2 of N was applied at the time of sowing and remaining 2 N was applied at the time of 1st irrigation. The system of layout was Randomized Complete Block Design with four replications. The net plot size was 6H4 m. Fertilizer sources of NPK were urea, TSP and SOP, respectively. Wheat variety inqulab-91 was sown as test crop. The yield and yield components data was recorded and grain and straw samples were analysed for K contents. Soil samples after harvesting the crop were also collected and analysed for the extractable soil K. The results indicated that increasing rates of potassium fertilizer increased the number of tillers mG2, plant height (cm), 1000-grain weight, grain and straw yield significantly. Maximum grain (3.06 t haG1) and straw (3.57 t haG1) yield were found in T4 (90 kg K2O haG1). Increasing rates of potassium fertilizer increased concentration of potassium in grain and straw significantly. After harvesting the crop, the extractable potassium contents of soil increased from that of the original soil.
Soil salinity is indeed a global problem posing a major threat to the agriculture in the world. According to an estimate (El-Ashry et al., 1985) salinity is seriously limiting crop production on 20 million hectare in the world. In Pakistan 6.67 million hectare is salt affected out of which 56 % is saline-sodic (Soil Survey of Pakistan, 1965).
Wheat yield on slightly and moderately salt affected soils is reduced by 36 and 68%, respectively, as compared to those obtained on non-saline-sodic soils (Qayyum and Malik, 1988). Because in saline sodic soils Na competes with K and reduces its uptake and causes potassium deficiency (Carden et al., 2003). Jami (1982) recorded the effect of soil salinity on number of tillers, leaves, fresh and dry weight of shoots and roots in case of wheat and pointed out that all these parameters were adversely affected due to high salinity. Niazi et al. (1992) conducted a pot experiment to evaluate the effect of potassium under different artificially developed sodicity levels for wheat and rice. K levels were 0, 15, 30, 45 and 60 mg kg-1 soil and developed sodicity levels (ESP) were 5.4 (initial), 18 and 34. They found that increasing sodicity levels decreased the grain yield, straw yield and productive tillers. K concentrations and its uptake in grain and straw were increased significantly with its increasing application. Hussain et al. (1992) conducted a pot experiment to note the potassium effect on wheat at different salinity levels i.e., 8, 12 and 16 dS m-1.
Potassium levels were 0, 15, 30, 45 and 60 mg kg-1 soil. The results showed that the grain and straw yields of rice and wheat decreased with increasing salinity levels. In wheat, K concentration and its uptake were significantly increased up to 30 mg kg-1 application rate and further increase in K proved ineffective. Saifullah (2002) studied the effect of potassium on growth and yield of wheat in saline sodic soil. Five rates of potassium (0, 75, 150, 225 and 300 kg ha-1) were tested in the presence of basal doses of N and P2O5 i.e., 140 and 110 kg ha-1, respectively. Yield, its components and K contents were increased while Na contents were decreased. Keeping all this in view present study was conducted to see the response of wheat to applied potassium in saline sodic soil.
MATERIALS AND METHODS
A field experiment was conducted at the research farm of Soil Salinity Research Institute, Pindi Bhattian, during the year 2005-2006. Before sowing of the wheat, a composite soil sample was collected from the experimental field. The soil sample was air-dried, ground, well mixed and passed through a 2 mm sieve and analyzed for the physical and chemical characteristics.
Four rates of potassium i.e., 30, 60, 90 and 120 K2O kg ha-1
beside control were applied. A basal dose of 140 and 110 ( kg ha-1)
of N and P2O5, respectively was also applied. The system
of lay out was Randomized Complete Block Design with four replications. Net
plot size was 6x4 m. The field was plowed thoroughly for seedbed preparation
and divided into 15 plots. Wheat variety inqulab-91 was sown as test crop on
21 November, 2005. Nitrogen, phosphorus and potassium were applied as urea,
tripple super phosphate and potassium sulphate, respectively. The whole of P,
K and ½ of N was applied at the time of sowing and remaining ½
of N was applied at the time of 1st irrigation. The crop was harvested at maturity
on 24 April 2006 and number of productive tillers, plant height and 1000-grain
weight (g), grain and straw yield (t ha-1) data was recorded. Plant
samples (grain and straw) were collected at the harvest of the crop. The samples
were oven dried, ground and analyzed for potassium. All the soil and plant analysis
was done according to the methods given in Hand Book No. 60 (US Salinity Laboratory
Staff, 1954) except texture by Moodie et al. (1959) and available soil
phosphorus by Watanabe and Olsen (1965).
The statistical analyses of data were carried out by applying analysis of variance technique (Steel and Torrie, 1980) and treatment means were compared using the Least Significant Difference Test.
RESULTS AND DISCUSSION
The original soil analysis before the sowing of wheat is given in Table 1. The soil was sandy loam in texture, saline-sodic in nature, low in organic matter and P and medium in K.
Effect of potassium application on the growth parameters and yield of wheat
Yield parameters of wheat: The yield of crop is the estimation of
all the yield components, of which the number of tillers per unit area, plant
height and 1000-grain weight are the most important components. The data regarding
the effect of potassium application on the number of productive tillers, plant
height and 1000 grain weight is presented in Table 2. The
results showed that all the three parameters increased significantly with the
application of potassium fertilizer up to 90 kg K2O ha-1
and higher application rates of K2O remained ineffective in increasing
It is clear from the data that when we increased the potassium fertilizer rate, these parameters increased significantly. This might be due to more uptake of potassium from salt affected soil where K was applied. The increased response of wheat to increasing levels of K application in this saline sodic soil was due to antagonistic interaction between Na and K. High salinity levels lead to Na toxicity accompanied by potassium deficiency (Muhammed, 1986) and thus higher rates of K2O up to 90 kg ha-1 increased number of productive tillers. These results are similar to those reported by Macleod (1969), Gulshad (1985) and Azam (1993) in salt affected soil.
This increase in plant height was due to the greater availability of K, which regulated the stomatal opening and closing and maintained osmotic or solute potential in plants due to which growth of cells and tissues remained continuous (Sinha, 1978). The increase in 1000-grain weight was due to the positive effect of K on wheat yield under saline-sodic soil. Actually K has significant role in starch synthesis and in grain development (Mengal, 1982) thus its adequate supply showed a profound effect in producing heavier wheat grains. Similar results were found by Gulshad (1985), Hussain et al. (1992) and Niazi et al. (1992) in salt-affected soil.
Grain and straw yield of wheat (t ha-1): The grain yield
is a function of the combined contribution of various yield components that
have direct relationship to the growing conditions and practices adopted to
manage the crop. The data showing the grain and straw yields of wheat crop are
given in Table 2. The results revealed that the potassium
fertilizer treatments gave significantly higher yield than the control. The
minimum yield of wheat grain (2.52 t ha-1) and wheat straw (2.91
t ha-1) was found in T1 (control). Low yield in T1
(control) was due to salinity sodicity in the rooting zone and low fertility
status with respect to NPK.
and chemical characteristics of soil before sowing of wheat
of potassium application on growth parameters and yield of wheat
concentrations in wheat grain and straw (%)
of potassium application on extractable potassium content (mg kg-1)
in soil after harvesting of wheat
There are many causes of low yield under saline-sodic conditions and were discussed
earlier by various workers including Chhabra (1983) and Muhammed (1986). According
to them high salinity sodicity levels lead to potassium deficiency due to antagonistic
effect of Na on potassium absorption or disturbance of the Na+/K+
Maximum wheat grain (3.06 t ha-1) and straw (3.57 t ha-1) yield was found in T4 (90 kg K2O ha-1) that was at par with T5 (120 kg K2O ha-1) and followed by T3 (60 kg K2O ha-1) and T2 (30 kg K2O ha-1). These results are in accordance with the findings of MacLeod (1969), Chhabra (1983), Gulshad (1985), Farooq (1989), Niazi et al. (1992), Azam (1993) and Singh (2005). It is clear from Table 2 as potassium level was increased in saline-sodic soil, yield increased significantly. This might be due to more uptake of potassium from the salt affected soil where potassium fertilizer was applied.
Effect of potassium application on K concentrations in wheat grain: The data of potassium concentration in wheat grain is given in Table 3. The results indicated that minimum K conc. (0.36%) was observed in T1 (control) while maximum (0.42%) was found in T5 (120 kg K2O ha-1), T4 (90 kg K2O ha-1) and T3 (60 kg K2O ha-1) followed by T2 (30 kg K2O ha-1). The treatments T5, T4 and T3 were statistically non-significant but they were significant over control (T1). These results are in line with those of reported by Anonymous (1982), Ohno and Grunes (1985), Muhammed (1986), Fageria et al. (1990), Niazi et al. (1992), Logbina and Bugaevskii (1992), Hussain et al. (1992), Azam (1993) and Singh (2005).
Effect of potassium application on concentrations of K in wheat straw:
The data regarding the effect of potassium application on the concentrations
of K, in wheat straw is presented in Table 3 which, showed
that concentrations of K increased significantly with the use of potassium fertilizer.
Minimum K concentration (1.31 %) was observed in T1 (control) while
maximum (1.42 %) was found in T5 (120 kg K2O ha-1)
followed by T4 (90 kg K2O ha-1), T3
(60 kg K2O ha-1) and T2 (30 kg K2O
ha-1). The treatments T5 and T4 in potassium
concentration were statistically nonsignificant with each other and significant
over T2 and control (T1). The increase in potassium concentration
of wheat straw with potassium fertilizer treatments might be due to higher uptake
of K by plants (Chhabra, 1983; Muhammad, 1986). These results are in line with
findings of those reported of reported by Anonymous (1982), Ohno and Grunes
(1985), Muhammed (1986), Fageria et al. (1990), Niazi et al. (1992),
Logbina and Bugaevskii (1992), Hussain et al. (1992), Azam (1993) and
Effect of potassium application on extractable soil K after wheat harvest: The effect of potassium fertilizer on the extractable potassium contents in saline-sodic soil after harvesting the wheat crop is given in Table 4.
The results revealed a significant difference among treatments. Maximum extractable soil potassium (130 mg kg-1) was found in T5 (120 kg ha-1) followed by T4 (90 kg ha-1), T3 (60 kg ha-1) and T2 (30 kg ha-1). Minimum extractable potassium (112 mg kg-1) was found in T1 (control). Over all the treatments were statistically significant to each other and over control (T1).
Saline soils are generally medium to high in available potassium (Sharma et al., 1968) but plants grown under high salinity may show K deficiency due to antagonistic effect of Na+/K+ or disturbed Na+/K+ ratio (Chhabra, 1983). In T5 maximum extractable potassium was found because here maximum potassium fertilizer (120 kg ha-1) was applied. The original level of extractable K in soil was 118 ppm and after wheat harvest, analysis showed 112 ppm extractable K in the control plots. Similar results were found by Chaudhary (1981), Azam (1993) and Singh (2005).
In saline sodic soils, maximum wheat yield and yield components i.e., No. of tillers m-2, plant height (cm), 1000-grain weight, grain and straw yield can be obtained at 90 kg K2O ha-1.
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