Effect of Phosphate rock on soil characteristics and nutrient uptake of wheat under Old Brahmaputra Floodplain soils.

Md.Nurul Huda Al Mamun and Md.Safinur Rahman


Abstract

A study was conducted to observe the direct and residual effects of phosphate rock (PR) on the growth and yield of wheat (cv.Kanchan) during rabi season of 2004-2005 under Old Brahmaputra Floodplain soil at Bangladesh Agricultural University Farm, Mymensingh. The experiment was designed with four treatments and laid out in a Randomized Complete Block Design (RCBD) with four replications of each treatment. The treatment combinations were T1: control (0 kg P ha-1),T2 : PR(26 kg P ha-1),T3 :TSP(26 kg P ha-1) and T4: PR(210 kg P ha-1 was applied in previous crop to cover 6 succeeding crops). Nutrient Content and uptake by wheat plant varied significantly with P treatments. The yield due to different treatments ranked in the order of T3>T4>T2>T1.The maximum N,P,K and S contents as well as uptake by wheat plant in grain and straw were recorded in T3 treatment. The Characteristics of the post harvest soil as influenced due to different treatments. The highest nutrient content of post harvest soil like pH, Organic matter, P and K were found in T3 treatment.

1. Introduction

Bangladesh is agrarian country, where agriculture is the single largest sector. Economic development of the country basically rests on agricultural development. It accounts for almost above one – third (35%) of Gross Domestic product (GDP) and provides employment for two-thirds of the labor force (Sarker and Islam, 2001).Wheat (Triticum aestivum L.) is the most important cereal crop and ranks third both in acreage and production of the world (UNDP and FAO,2008).It has been established as the second most important staple food crop after rice in Bangladesh (Razzaque and Hossain,1999).Bangladesh produces 12,53,000 metric tons of wheat per annum from 15,86,000 acres of land (BBS,2004).The cereal crop production like wheat should be increased to meet the demand of the escalating population of Bangladesh, where an individual requires 454 g cereal food (BARI,2004).The Soil and climate of Bangladesh is favorable in winter for wheat production but the average yield of wheat in this country is quite low as compared to that of many wheat growing countries of the world. Improper management of fertilizers is one of the major causes of low production because fertilizer plays an important role in augmenting yield of wheat. Phosphorus is the second key plant nutrient needed in adequate quantity in available source of growth, reproduction, yield and quantity of crop. The phosphorus content of Bangladesh soils is being depleted day by day due to crop removal particularly in intensive culture. So, application of phosphatic fertilizers is recommended for all soils and crops in Bangladesh to obtain better yield (BRAC, 2005).Triple super phosphate (TSP) is the main source of phosphorus, where single super phosphate (SSP) is water soluble and newly introduced phosphetic fertilizer in Bangladesh and its popularity has been increasing day by day. Rock phosphate (PR) is another source of phosphorus. It is the cheapest and economic source of phosphorus (Hoffland, 1991) which is not being used in the crop field due to its insolubility. The direct application of finely ground rock phosphate (PR) may be an attractive alternative to the use of more expensive soluble P-fertilizer for certain crops and soils (Hammond et al., 1986).But in Bangladesh, a little research work has been done in this aspect. Keeping this in this view, the present research has been set up to compare the effect of direct application of PR and TSP on growth and yield of wheat, to study the response of wheat as affected by residual effects of high rate of PR applied in preceding T.aman crop and to compare economic benefits of PR with TSP as the source of P on wheat.

2. Materials and Methods
2.1. Site description

The field experiment was carried out with wheat (cv.Kanchan) grown in sequence after aman rice under some selected treatments. The experiment was set up at Soil Science field Laboratory of Bangladesh Agricultural University, Mymensingh under Old Brahmaputra Floodplain (AEZ 9) agro-ecological region of Bangladesh during the Rabi season of 2004-2005.The farm belongs to the general soil type Non-calcareous Dark Grey Floodplain soil under Sonatal series.

2.2. Treatments and design

The experiment was laid out in a Randomized Complete Block Design (RCBD) with 4 replications. Each block was sub-divided into 4 unit plots. The total number of plots was 16(4X4) and the unit plot size was 8mX5m.The spacing between blocks was 1m and between plots 0.3m.There were four treatments consisting of TSP and two rates of rock phosphate (PR) and a control. The treatment combinations were T1: control (0 kg P ha-1), T2: PR (26 kg P ha-1), T3: TSP (26 kg P ha-1) and T4: PR (210 kg P ha-1 was applied in previous crop to cover 6 succeeding crops).

2.3. Fertilizer application, transplanting and intercultural operations

The experimental field was first opened on 20 days before sowing with the help of power tiller and cross-ploughed 6 times. All kinds of weeds and residues of previous crop were removed from the field. The plant nutrients like Nitrogen, Phosphorus, Potassium, Sulphur and Boron were used in the research field as 100kgN ha-1,26kgP ha-1,33kgK ha-1,20kg S ha-1and 1kg B ha-1 respectably. All fertilizers except N were applied to the soil during final land preparation. Nitrogen as urea was applied in two times; firstly 2/3 of urea was applied during final land preparation. Remaining 1/3 urea was applied as top dressing at the time of 21 days after emergence of seedlings. The seed was shown on November 20, 2004 and seed rate was 120 kg ha-1as recommended by BARI (2003).Line to line distance was 20 cm with continuous distribution of seeds in the lines in each plot. Inter cultural operations such as irrigation, weeding and pest control etc. were done as and when required.

2.4. Harvesting and data collection

At the spike emergence stage and at harvest the plant samples were collected from each plot. Ten hills per plot were collected randomly for the determination of dry matter yield and nutrient analysis. The crop was harvested at full maturity on 14 March, 2005.Sun dried weight of both grain and straw were recorded plot-wise for each treatment.

2.5. Chemical analysis of soil and plant samples

The initial soil sample was collected before land preparation from 0-15 cm and analyzing for both physical and chemical properties in the Laboratory of the Department of Soil Science, Bangladesh Agricultural University, Mymensingh. Particle size analysis of soil was done by Hydrometer method (Gee and Bauder, 1986). Soil pH was measured with the help of glass electrode pH meter using soil water suspension of 1:2:5(Jackson, 1962).Organic carbon in soil was determined by wet oxidation method ( Walkley and Black,1934).Cation exchange capacity (CEC) of soil was determined by sodium saturation method as outlined by Chapman (1965). Total nitrogen of soil was estimated by micro kjeldhal method (Bremner and Mulvaney, 1982).Available soil phosphorus was measured by Olsen method (Olsen and Sommers, 1982).Exchangeable potassium was determined by using flame photometer (Black, 1965) and available sulphur was determined by turbidimetric method. The collected grain and straw samples from each plot were dried in an oven at 650C for 48 hours after which they were ground by a grinding mill. Later the ground samples were sieved through a 20- mesh sieve. The prepared samples were then chemically analyzed for N, P, K and S following diacid digestion procedure (Jones and Case, 1990; Watson and Issac, 1990).The analysis of variance for crop characters and also for the nutrient elements of plant samples were done following the F-test. Mean comparisons of the treatments were made following the Duncan’s Multiple Test (DMRT).

3. Results and Discussion
Nutrient Content and uptake at panicle initiation stage
3.1 Nitrogen content and uptake by wheat plant

Results in Table 1.showed that the N content in wheat plant at PI stage significantly influenced by different treatments. The maximum N content (1.26%) was obtained in T3 treatment while control treatment showed the m inimum N content (0.90%).But the treatments T3 and T4 were statistically identical. Nitrogen uptake by wheat (cv Kanchan) also varied significantly. The highest N uptake (28.35 kg ha-1) was obtained in T3 treatment and the minimum value (13.68 kg ha-1) was noted in control treatment.

3.2 Phosphorus content and uptake by wheat plant

The P content in wheat plant at PI stage was significantly influenced by different treatments .The P content ranged from 0.085 to 0.283%.The minimum content was obtained in the control and the highest P content was recorded in T3 treatment. A significant increase in P uptake by wheat plant was also obtained due to different treatment (Table 1).T3 treatment showed the maximum P uptake (6.37 kg ha-1) and control treatment showed the minimum P uptake (1.29 kg ha-1).P applied in the form of TSP was found to have better effect over PR having same rate of P application (26 kg P ha-1).

3.3 K content and uptake by wheat

The K content in wheat (cv.Kanchan) at panicle initiation stage was significantly influenced by different treatments and ranged from 1.09 to 1.28% .The highest value was obtained in T3 treatment, and control treatment showed the lowest K content. K uptake by wheat plant responded significantly due to different treatments ranged from 16.52 to 28.80 kg ha-1.The highest K uptake (28.80 kg ha-1) was indicated in T3 treatment and lowest value (16.52 kg ha-1) was noted in control.

3.4. S content and uptake by wheat plant

Result that S content increased significantly by different treatments. S content in wheat plant varied from 0.140 to 0.164%. The maximum value was noted in the treatment T3 and the control treatment showed minimum S content. S uptake by wheat plant also responded significantly due to different treatments. The highest S uptake (3.69 kg ha-1) was obtained in T3 treatment and the lowest value (2.13 kg ha-1) was found in control and the S uptake ranged from 2.13 to 3.69 kg ha-1. The treatments T2 and T4 were significantly identical.

Nutrient content and uptake in grain and straw
3.5. Nitrogen content in grain and straw

Application of PR and TSP exerted positive effect on the N content in grain. The concentration of N in grain ranged from 1.90 to 2.10% . The maximum N content was recorded in T3 treatment and the lowest N content was found in control treatment (T1) which was statistically identical to T2 and T4 treatments. On the other hand, N content in straw ranged from 0.442 to 0.641% and the maximum concentration of N content was obtained in the T3.TSP had shown better effect over PR (26 kg P ha-1) and T4(210 kg P ha-1) treatments.

3.6 .Nitrogen uptake in grain and straw

N uptake in grain and straw was influenced significantly due to application of PR and TSP.N uptake by grain ranged from 38.95 to 65.10 kg ha-1.The maximum N uptake was noted in T3 treatment and the lowest N uptake was recorded in control .The second highest N uptake was found in T4 treatment.Similarly, in case of straw, the highest N uptake (35.51 kg ha-1) was observed in T3 treatment and lowest N uptake (12.92 kg ha-1) was noted in control. The second highest N uptake (28.65 kg ha-1) by straw of wheat was found in T4 treatment.

Total N uptake ranged from 51.87 to 100.61 kg ha-1. The maximum total N uptake was found in T3 treatment and the minimum total N uptake was recorded in control. The second highest N uptake was observed in T4 treatment, which was treated as residual effect of PR. It may be explained that P fertilization increased the N content and uptake in cereals irrespective of different sources. Munson (1986) described that P enhanced N content as well as uptake in grain because of improved metabolism and utilization of other elements.

3.7. P content in grain and straw

The P content in grain and straw was significantly affected by the different treatments. The contents of phosphorus in grain varied from 0.233 to 0.301 % (Table 3).The maximum P content was observed in TSP treatment followed T4(0.29%) and T2 (0.284%).The minimum P content was observed in control treatment. The highest P content in straw was attained in T3 (0.159%) followed by T4 (0.143%) and T2 (0.101%) and the minimum P content was found in control treatment. However, in both cases TSP has shown better effect over PR having same rate of P. On the other case, TSP also had shown better performance over residual effect of PR in T4 treatment.

3.8. P uptake in grain and straw

Like P content, P uptake by grain and straw was influenced significantly due to different treatments. However, maximum P uptake was recorded in T3 (9.33 kg ha-1) treatment from TSP source and minimum P uptake (4.92 kg ha-1) was in control. Similar trend was also noticed in case of total P uptake. The total P uptake varied from 6.36 to 18.13 kg ha-1.Significant increase in P content as well as uptake with the application of P fertilizer was in corroboration with the findings of Agarwal (1976) and Hammond et al. (1986).

3.9. K content in grain and straw

The K content in grain ranged from 0.395 to 0.462% . The maximum K content was recorded in T2 treatment which was statistically identical with T3 (0.447%) and T4 (0.410%).The control treatment noted minimum K content (0.395%). In case of straw, K content also varied due to different treatments. All the treatments increased the K content significantly over control. The maximum K content (1.48%) in straw was found in T3 treatment which was statistically identical with T4 treatment and the minimum K content (1.29%) was obtained in control treatment.

3.10. K uptake in grain and straw

K uptake by grain ranged from 8.09 to 13.85 kg ha-1.The maximum K uptake was recorded in T3 treatment followed by T4 (11.68 kg ha-1) and then by T2 (10.00 kg ha-1).The lowest K uptake was found in control treatment. The same trend was observed in case of K uptake by straw. The highest K uptake was observed in T3 (81.99 kg ha-1) treatment followed by T4 (77.47 kg ha-1) and T2 (48.87 kg ha-1).The lowest K uptake (37.66 kg ha-1) was recorded in control. Results in Table 4. showed that total K uptake varied significantly (from 45.75 to 95.84 kg ha-1) due to different treatments. The maximum K uptake (95.84 kg ha-1) was recorded in T3 treatment and the lowest K uptake was observed in control. The second highest total K uptake was found in T4 treatment, where 210 kg P was applied in previous crop to cover six crops. P fertilizer appeared to have synergistic effect on the K content in grain and straw. Similar observation of increase in K content and uptake with the application of phosphetic fertilizers were reported by may investigators (Ararwal, 1978; Reddy and Bhardwaz, 1983).

3.11. S content in grain and straw

Application of PR and TSP exerted positive effect on S content in grain of wheat. The content of S in grain ranged from 0.269 to 0.328% . The highest S content was observed in T3 treatment which was statistically similar to that was observed in T4 (0.315%) treatment. The lowest S content was found in control treatment, but it was identical with T2. In case straw, the maximum S content (0.124%) was recorded in T3 treatment which was statistically identical to that of T2 and T4. The control treatment obtained minimum S control (0.098%).

3.12. S uptake in grain and straw

Results indicated that S uptake by grain was also significantly influenced by different treatments. The range of S uptake observed in grain was 5.51 to 10.16 kg ha-1.The maximum S uptake (10.16 kg ha-1) was recorded in T3 treatment and the lowest value (5.51 kg ha-1) was recorded in control. The second highest value (8.97 kg ha-1) was found in T4 treatment, which treated as residual effect of PR. In case of straw, the maximum S uptake was recorded in T3 treatment which was statistically identical to that of T4 treatment. The control treatment obtained minimum S uptake and the range was 2.86 to 6.86 kg ha-1. Application of PR and TSP had significant effect of total S uptake .The highest total S uptake (17.02 kg ha-1) was found in T3 treatment and the lowest total S uptake was observed in control treatment (8.37 kg ha-1). Works of different investigators (Joshi and seth, 1975; Ahmed, 1993) also revealed that the P fertilization increased S content and uptake of wheat grain.

3.13. Characteristics of post harvest soils

Result showed a marked variation on the soil pH, soil organic matter, N, P, K and S of the initial soil values. pH values of the post harvest soils ranged from 6.72 to 6.92,whereas the initial soil pH value ranged from 6.61 to 6.69. The highest pH value (6.92) was recorded in T3 treatment. The lowest pH value (6.72) was recorded in T1 treatment. The organic matter content of the post harvest soil range varied from 2.18 to 2.29% whereas the initial soil organic matter range varied from 2.21 to 2.34 %( Table 6). The maximum organic matter content (2.29%) of post harvest soil was observed in T3 treatment and the minimum organic matter content (2.18%) was obtained in control treatment. The total N content of the post harvest soil varied from 0.147 to 0.154% , where the initial soil total N varied from 0.145 to 0.149%. The highest total N was observed in control treatment and the lowest total N was found in T2 and T3 treatment. The variation of total N content value among the treatments was insignificant. Application of PR and TSP exerted significant effect on the available P in post harvest soil. The available P content in post harvest soil varied from 10.49 to 16.50 ppm, where the initial soil available P content range varied from 10.37 to 16.20 ppm. The highest available P content was recorded in the treatment T3 (16.50ppm) which was statistically significant with T4 treatment (16.25 ppm). The lowest available P content was found in control treatment. The variation of exchangeable K content value of post harvest among treatment was insignificant. The exchangeable K content of post harvest soils ranged from 0.126 to 0.135 cmol kg-1 whereas the initial soil exchangeable K content range varied from 0.125 to 0.131 cmol kg-1.The highest exchangeable K content was observed in T3 treatment (0.135 cmol kg-1) and the lowest exchangeable K content was found in control treatment (0.126 cmol kg-1).Available S content of post harvest soils influenced significantly due to different treatments . The maximum S content (14.55 ppm) was observed in control and the minimum available S content (13.37ppm) was observed in T3 treatment. The available S content of initial soil ranged from 12.06 to 14.51 ppm.

Conclusion: It can be concluded that the use of rock phosphate will entirely be a new source of P fertilizer to be used in the country. TSP had better performance over PR having same rate of P (26 kg P ha1) and (210 kg P ha-1 was applied in previous crop) which was treated as residual effect of PR. Treatment T4 showed comparatively better performance than T2 because of its (PR) low solubility. Although PR bear some toxic substances in soil but its low price and high residual effect of cropping system could be and added factor for easy acceptance of P fertilizer compared to other phosphatic fertilizers. The effect of TSP on nutrient contents as well as uptake by wheat plant in grain and straw was better than the direct application of PR. The residual effects of high rate of PR applied in preceding T.aman crop had shown better performance than the PR which was used in present wheat crop.

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