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Introduction

Wheat grain is one of the most important cereal crops in Bangladesh. The wheat yield in this country is low. There are several reasons that can explain the yield variation, which cover both biotic and abiotic factors. Among the biotic factors, unavailability of high yielding varieties,¹incidence of diseases and pests² and abiotic factors such as high temperature,³moisture stress⁴and nutrient deficiency^5,6,7are responsible for lower productivity of wheat in the tropics and sub-tropics.

The soils of northwest part of Bangladesh are light textured, low in organic matter and strongly acidic to moderately acidic in nature, pH ranges from 4.5 to 5.5.⁸The status of available P, Ca and Mg of these soils are low. The sandy soil has low cation exchange capacity. These soils have high content of aluminum, iron, and manganese⁹and deficiencies of nitrogen, calcium, magnesium, potassium, phosphorus and boron are common. Aluminum toxicity is responsible for poor yields in acid soils.¹⁰

Liming on acid soil increases the pH level, decrease Fe, Al and Mn toxicity, increase the availability of N, P, Ca and Mg and microbial activities. In acid soils application of lime and farmyard manure significantly increased water- soluble nitrogen and fixed ammonium. Therefore, a study was under taken in a highly acidic soil of Dinajpur, to see the changes in chemical properties of soil due to liming in wheat field and to evaluate the effect of lime on yield, yield contributing characters and nutrient composition of wheat.

Material and Methods

The experiment was conducted in the farm of Hajee Mohammad Danesh Science and Technology University, Dinajpur from November 2006 to March 2007. The experimental field is located at 25038½ N latitude and 88o41½ E longitude at a height of 34.5 m above the mean sea level. It belongs to the Agro Ecological Zone 1 (Old Himalayan Piedmont plain). The soil was sandy loam having pH 4.85, organic matter 0.96%, total N 0.06%, available P 43.36 µg g-1, K 0.18 meq 100 gsoil^-1, available Ca 1.21 meq 100 gsoil^-1, Mg 0.39 meq 100 gsoil^-1and S 2.72 µg g^-1. The test crop was wheatTriticum aestivum cvBijoy for the study. Certified seeds were collected from the Wheat Research Centre, Nashipur, Dinajpur. There were eight different doses of lime application in wheat as follows T₁(Control); T₂, 0.5 t ha^-1lime; T₃, 1.0 t ha^-1lime; T₄, 1.5 t ha^-1lime; T₅, 2.0 t ha^-1lime; T₆, 2.5 t ha^-1lime; T₇, 3.0 t ha^-1lime and T₈, 3.5 t ha^-1lime. The liming material had 20% Ca and 10% Mg. The liming material was applied to the soil on 1 November 2006 and mixed well with soil by repeated ploughing by power tiller and country plough. Final land was prepared on mid November, 2006.

The exper iment was laid out in a Randomized Complete Block Design with three replications. There were altogether 24 (8´3) unit plots (5´4 m). Inter-block and Inter-plot spacing were 1m and 0.7m, respectively. Fertilization was as N @ 130 kg ha-1from urea, P @ 5.5 kg ha-1from TSP, K @ 54 kg ha-1from MoP, S @ 33 kg ha-1from gypsum, Zn @ 3.6 kg ha-1from zinc sulphate (monohydrate) and B @ 0.6 kg ha-1 from boric acid.

表1:石灰对土壤道具的变化erties of post harvest soils of wheat field Click here to view table

三个治疗应用,第一个irrigation after 12 days of sowing, second irrigation after 22 days of sowing at crown root initiation stage and the third after 58 days of sowing at heading stage. Weeding and pest control program were done when necessary.

The crop was harvested at maturity after about four months of sowing (March 23, 2007). Ten plants from each plot were sampled randomly recording for yield parameters. Then plot- wise weights of grain and straw were recorded.

Table 2: Effects of lime on growth and yield components of wheat Click here to view table

Analysis of Soil and Plant Samples

Soil samples were collected randomly from 10 different spots of the field from a depth of 0-15 cm. After harvest of wheat, the soil samples from each plot were collected at a depth of 0-15 cm. The initial soil samples were analyzed as per standard methods for soil texture, pH, organic matter, total N and available P, K, S, Ca, Mg, contents[11]. The post harvest soils were analyzed for soil pH, available P, Ca and Mg. Plant extract for grain and straw were prepared by wet oxidation method using diacid (HNO₃: HClO₄= 2:1) mixture method. Phosphorous content was estimated by developing blue colour absorbance with Ammonium molybdate- ascorbic acid solution and measur ing the colour by spectrophotometer at 890nm wavelength12. Ca and Mg from the plant extract were determined by AAS. Sulphur from the extract was determined by turbidimetrically using barium sulphate by spectrophotometer. The data were analyzed statistically¹³by F-test to examine whether the treatment effects were significant or not. The mean comparisons of the treatments were evaluated by DMRT (Ducan’s Multiple Range Test) if the treatments were significant. The analysis of variance (ANOVA) for different parameters was done by a computer package programme “MSTATC”.

Table 3: Effects of lime on grain and straw yields of wheat Click here to view table

Results and Discussion

Chemical Properties of Post Harvest Soils

The changes in pH, P, Ca and Mg content in soil markedly varied after the harvest of wheat. The pH values, P, Ca and Mg availability of the post harvest soils in different treatments of wheat increased steadily with increasing rates of lime application (Table 1 and Fig. 1a). The pH of the initial soil was 4.85 which increased to 5.20, 5.66, 5.98, 6.10, 6.39, 6.54 and 6.64 in T₁, T₂, T₃, T₄, T₅, T₆, T₇and T₈respectively. The increased in soil pH was due to available of Ca and Mg in soils (Figs. 1a,b and c). The initial value of available phosphorus in the soil was 43.35 µg g^-1soil and the post harvest soils had the values 43.77, 44.10, 45.41, 46.52, 47.34, 47.57, 48.42 and 53.27 ìg g^-1soils in T₁, T₂, T₃, T₄, T₅, T₆, T₇and T₈respectively. The status of available P of soils was positively correlated with the rates of lime application (Fig. 1d). Lime application increased the soil pH which helped the release of fixed P from the oxides and hydroxides of Fe and Al thus increased the P availability in soils.The available Ca of the initial soil was 1.21 me 100 gsoil^-1which increased to 1.22, 1.51, 1.44, 1.83, 2.11, 2.16, 2.30 and 2.55 meq 100 g soil-1 in T₁, T₂,T₃, T₄, T₅, T₆, T₇and T₈respectively. The liming material used as dolomite (CaCO₃.MgCO₃), which on dissolution released a large amount of Ca & Mg and thus the available of Ca increased in post harvest soils. The available Mg of the initial soil was 0.39 meq 100 g soil-1 which increased to 0.42, 0.46, 0.60, 0.84, 1.11, 1.12, 1.22 and 1.41 meq 100 gsoil^-1in T₁, T₂, T₃, T₄, T₅, T₆, T₇and T₈treatments respectively.

Figure 1: Relationship between soil pH, available P, Ca and Mg with lime rate Click here to view figure

Yield Components

The application of different rates of lime significantly increased the plant height, the number of tillers plant^-1, spike length, the number of spikelets spike-1 and the number of grains (Table 2). Plant height of wheat progressively increased with increase in lime rates. The plant height ranged from 85.38 cm in T₁(control) treatment to 112.60 in T₈treatment. The tallest plant recorded in T₈was significantly comparable to those obtained in T₅, T₆and T₇treatments. All the treatments of T₁, T_2,T₃and T₄differed statistically from each other in plant height. The number of tillers plant^-1by different treatments varied from 2.09 to 4.03. The highest number of tillers was obtained in the treatment T₈, which was statistically similar with T₇和优于其他治疗。应用ts T₆and T₅recorded the identical number of tillers plant^-1. Again the treatments T₄and T₅were statistically identical in producing tillers plant^-1. The treatments T₄and T₃were also statistically identical and superior to T₂and T₁treatments.

Spike length of wheat ranged from 7.83 to 14.20 cm, tallest spike was found in T₈treatment which was statistically similar to T_7.应用t T₇recorded the spike length of 13.5 cm which was comparable to those found in T₆and T₅treatments. The treatment T₄was statistically superior to T₂and T₃treatments in terms of spike length. The treatments T₂and T₃were identical in recording spike length. spikelets spike^-1ranged from 10.2 in T₁treatment to 20.1 in T₈treatment. The number of spikelets spike^-1was found maximum in T₈treatment which was statistically similar to T_7.The number of spikelets spike^-1in T₇was statistically identical to those found in T₅and T₆treatments. The treatment T₄was superior to T₃treatment in recording the number of spikelets spike^-1. The number of spikelets spike^-1in T₃was statistically superior to the spikelets spike^-1recorded in T₂treatment. The number of grains spike^-1of wheat ranged from 29.8 to 41.6. The highest number of grains was found in T₇treatment which is statistically similar to all the treatments except T₁and T₂. The treatments T₃and T₂recorded identical number of grain spike^-1. Again the treatment T₂recorded higher number of grains spike^-1over T₁treatment but they were statistically alike. Liming had non significant effect on the 1000-grain weight of wheat (Table 2). The 1000- grain weight of wheat varied from 48.4 g to 50.7 g. The 1000 grain weight for T₆was highest (50.7 g) and the lowest was in T₂(48.4 g). The 1000 grain weight for T₅was in 2nd highest (50.3 g).

Table 4: Correlation between grain yields with yield parameters of wheat Click here to view table

Grain yield of wheat (var. Bijoy) was significantly responded due to application of different rates of lime (Table 3). The highest grain yield was found in T8 (4661 kg ha-1) while the lowest in T1 treatment. The treatments T5, T6, T7 and T8 produced statistically identical grain yields of wheat. The treatments T3 and T4 recorded identical grain yields of wheat. The application 0.5 t lime ha-1 (T2) significantly increased the grain yield of wheat compared to control treatment. Application of lime increased grain yield of wheat to a considerable extent but application of lime at the rate of 2.0 t ha-1 was enough for desired yield of wheat. The application of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 t lime ha-1 recorded 14.6, 23.0, 28.3, 37.9, 36.1, 37.6 and 37.9% yield increase compared to lime control treatment (Table 3) The grain yield of wheat was positively correlated with different plant characters like plant height (r=098**), spike length (r=0.97**), spike let spike-1 (r=0.98**), grains spike-1 (r=0.98**) and 1000-grain weight (r=0.83*) (Table 4). The grain yield of wheat was affected due to changes in soil properties due to liming. The grain yield was quadratically related with soil pH (R2=0.9354), available P (R2=0.937**), available Ca (R2=0.943**)and available Mg (R2=0.9572**) (Fig. 2). It appears that liming increased soil pH and availability of nutrients which increased the yield components of wheat finally higher yields of wheat. The application of lime 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 t ha-1 recorded 14.6, 23.0, 28.3, 37.9, 36.1, 37.6 and 37.9% yield increase compared to lime control treatment. Surface liming caused increases up to 140% in the grain yield of wheat.¹⁴Besides mineral and organic fertilization, liming also rendered significantly higher yields compared to the control and relatively higher yields than treatments involving mineral fertilizers.¹⁵Liming considerably influenced the yields of the field crops and single application of high rates was the better choice compared with repeated use of low rates¹⁶. The highest straw yield of 5896 kg ha-1 was observed in T7 treatment and was statistically identical to those found in T5, T6 and T8 treatments (Table 3). The treatments T4, T5 and T6 were also statistically identical. The treatment T4 was different from T2 and T3 treatments. The treatment T2 showed statistically higher straw yield compared to that found in T1 treatment. The application of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 t lime ha-1 recorded 12.5, 21.5, 27.2, 29.9, 31.8, 33.6 and 33.3% yield increase compared to lime control treatment.

Table 5: Effects of lime on phosphorus and sulphur, Calcium and Magnesium concentrations in wheat Click here to view table

Nutrient Concentration in Wheat

The application of lime to wheat increased the P concentration in grain and straw but such increase was not statistically significant (Table 5). The grain P concentration ranged from 0.29 % in T₁treatment to 0.39 % in T_5.In straw, P concentration ranged from 0.025 % in T₁to 0.040 % in T_7.The S concentrations of grain and straw were affected significantly due to application of different rates of lime (Table 5). All the liming treatments showed statistically identical grain S concentration but significantly higher than the lime control treatment (T₁). In case of wheat straw, the S concentrations in all of the liming treatments were statistically identical. The treatment T₂showed statistically identical straw S concentration with lime control treatment (T₁).

Figure 2: Relationship between soil pH, avail. P, Ca and Mg with grain yield of wheat Click here to view figure

The concentration of Ca in wheat grain remained unaffected due to lime application while in straw it was significantly increased (Table 5). The concentration of Ca in straw was much higher compared to those of straw. The concentration of Ca in wheat grain ranged from 0.037% in T₇to 0.051% in T₆treatment. In wheat straw, the highest Ca concentration of 0.318% was noted in T₈treatment which was statistically identical to those found in T_4,T_5,T₆and T₇treatments. Again the treatments T_2,T_3,T_4,T_5,T₆and T₇were statistically identical in recording the Ca concentration in wheat straw. The concentration of Mg in wheat grain was significantly increased while the concentration in straw remained unaffected due to the application of different rates of lime (Table 5). In grain, the application of all rates of lime showed identical concentration of Mg but superior to control treatment. In wheat straw, the concentration of Mg increased due to liming but such increase was not statistically significant. The Mg concentration in wheat straw ranged from 0.053% in T₁treatment to 0.062% in T₅treatment.

Table 6. Effects of lime on phosphorus, sulphur, calcium and magnesium uptake by wheat Click here to view table

Nutrient Uptake

Total P uptake by wheat was significantly affected by different rates of lime application (Table 6). The highest total P uptake was found in T₅treatment which was statistically identical to those found in T_4,T_6,T₇and T₈treatments. Again the treatments T_7,T_8,T_1,T_2,T_3,and T₄were statistically identical in terms of total P uptake. Total S uptake by wheat was significantly affected by different rates of lime application (Table 6). The highest total S uptake was found in T₈treatment which was statistically identical to those found in T_4,T_5,T₆and T₇treatments. Again the treatments T_3,T₄and T₅were statistically identical in terms of total S uptake. The treatment T₂recorded higher total S uptake compared to that of T₁treatment but such increase was not statistically significant.

Total Ca uptake by wheat was significantly affected by different rates of lime application (Table 6). The highest total Ca uptake was found in T₈treatment which was statistically identical to those found in T_5,T₆and T₇treatments. Again the treatments T_4,T_5,T_6,and T₇were statistically identical in terms of total Ca uptake. The treatments T₂and T₃were statistically identical and superior to control treatment (T₁).

The highest total Mg uptake by wheat ranged from 3.42 kg ha^-1in T₁treatment to 6.48 kg ha^-1in T₇treatment which was statistically identical to those found in T_5,T₆and T₈treatments. The treatments T_4,T₆and T₈were statistically identical in terms of total Mg uptake by wheat. The treatment T₂recorded significantly higher amount of total Mg uptake by wheat compared to T₁treatment.

It appears that lime application in Old Himalayan Piedmont Soil (AEZ 1) increased soil pH, availability of nutrient which in term of increased yield of components and yield of wheat. It is inferred that the amount of lime 2.0 t ha^-1may be optimum for wheat cultivation in the AEZ 1.

References