AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA ISSN Print: 2151-7517, ISSN Online: 2151-7525, doi:10.5251/abjna.2014.5.2.68.77

© 2014, ScienceHuβ, http://www.scihub.org/ABJNA

Screening of soybean varieties for phosphorus use efficiency in nutrient solution

Ochigbo, A.E. and Bello, L.L.

Department of Plant Breeding and Seed Science University of Agriculture, Makurdi.

Email address: Ochigbo_ene@yahoo.com

ABSTRACT

Thirty-seven tropically adapted soybean (Glycine max Merrill) varieties were screened at the crop science laboratory of the University of Agriculture, Makurdi using hydroponics. The experiment was a split plot in a randomized complete block design with three replications. Phosphorus levels (0, 0.5, 1.0, 2.0 mMol) were the main plots while the subplots were the soybean varieties. The seeds were germinated in trays for four days and healthy, uniform sized seedlings were transplanted into hydroponics nutrient solution where they remained for four weeks and then harvested. The dry matter was analyzed for phosphorus concentration for all the varieties. Data taken were subjected to analysis of variance which indicated difference in soybean response to P-level. The thirty-seven soybean varieties were classified into twenty one efficient and sixteen non efficient. Of the lowest P-level, the efficient varieties had the highest values for total dry matter and efficiency index.

Key words:- Hydroponics, efficiency index, efficient, inefficient, soybean

INTRODUCTION

Soybean (Glycine max L. Merrill) is a multipurpose grain legume crop in the tropics. It is a source of vegetable protein for many Nigerians and regarded as “meat for the poor” (Nworgu, 1993). World interest and attention in soybean is mainly due to its high nutritional value. When oil is extracted from soybean the residue left is used as protein supplement in livestock feeds.

Soybean requires adequate phosphorus supply for satisfactory nodule production and nitrogen fixation. Phosphorus has consistently increased grain yield of soybean on phosphorus deficient soils (Pal et, al. 1983, Chiezey et, al. 1991 and 1992) as it also encourages production and retention of more pods per plant (Chiezey, 2001).

Soils in the tropics are characterized with low phosphorus availability and this limit soybean production. To achieve high productivity in soybean, the soil is usually amended using fertilizers. These fertilizers are not readily available or are too expensive.

The aim of this study is to identify soybean varieties that have high phosphorus use efficiency or those that are tolerant to phosphorus deficiency using nutrient solution technique (hydroponics). This

method has great advantages as it could be used to screen large population of plants, it requires simple and rapid tests techniques, plants could be closely observed and the experiment can be regulated.

Previous studies on hydroponics screening are mainly in the temperate/ subtropical regions of the world where prevailing weather for most part of the year is unfavourable for optimum growth of soybean. Prevailing atmospheric temperature and relative humidity for most part of the year coupled with the daily sunshine in the tropics favour soybean growth. This also makes hydroponics screening possible at room temperatures (25

0C-32

0C) on laboratory tables

at anytime of the year without incurring cost of controlling the temperature, relative humidity or light.

MATERIALS AND METHODS

The study was carried out in the crop science laboratory of the University of Agriculture, Makurdi situated in the Southern Guinea Savanna ecological zone of Nigeria in 2008.

Thirty seven tropically adapted varieties released from International Institute of Tropical Agriculture (IITA) were used for this study. The experiment was laid out in a split plot in a randomized complete block design with three replicates. The main plot was the

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phosphorus levels while the subplots were soybean varieties.

Fifty healthy seeds of each variety were sterilized in dilute sodium hypochlorite solution for one minute. The seeds were then rinsed with deionised water and placed on moist papers in a tray for germination for ten days.

After ten days, ten vigorous, healthy, uniform sized seedlings of each variety were transferred into hydroponics nutrient solution- a modification of Hoagland (1919) solution as described by McClure and Isreal (1979).

The nutrient solution was then shared into four 15 litres plastic containers with removable lids to accommodate the four levels of phosphorus (0, 0.5, 1.0 and 2.0 mM/l). Each lid had forty holes arranged diagonally into which seedlings were transplanted with a central opening into which an aerator was connected that continuously bubbled air into the

solution. Ten uniform- sized seedlings were transplanted into the nutrient solution. This was replicated three times and nurtured for four weeks. Seedlings were closely observed.

The pH of the solution was taken daily and monitored to remain between 6 and 7.5 during plant growth.

Each variety was then harvested after four weeks of growth and analysed for phosphorus concentration with Vanado- molybdate method using colorimeter (Adisa, 1978).

Data taken include shoot length, root length, leaf number per plant, dry matter weight, phosphorus concentration in dry matter and phosphorus efficiency index (EI).

All data were then subjected to analysis of variance and the results of the efficiency index calculated were used to classify the varieties into efficient or non efficient users of phosphorus.

RESULTS

Mean squares estimates from analysis of variance for shoot length, and other yield attribute attributes is presented in Tables 1,2 and 3 for the early, medium and late varieties respectively used for the study. There were significant differences at 5% level of probability among varieties and within the phosphorous levels for all variables recorded. The interaction between variety and phosphorus level also showed significant difference for all variables in the early, medium and late varieties except shoot length and leaf number of the late variety which showed no significance at 5% level of probability. Since significance existed, this indicates that different varieties responded differently to phosphorus application. Effect of phosphorus treatments on soybean dry matter are presented on tables 4, 5 and 6 for early, medium and late varieties respectively. From the results, we observe that the dry matter which was made up of shoot and roots increased as application of phosphorus increased.

Among the early varieties TGX 1892-10F accumulated the highest dry matter of 1.35g while TGX 1485-ID accumulated the least at 2.0mM/l. In the medium varieties the dry matter weight ranged between 0.61g and 1.53g with variety TGX 1838-5E accumulating a dry matter of 1.00g at the lowest P-level. At 2.0mM/l TGX 1894-3F produced the highest dry matter of 1.53g followed by TGX 1882-

2F with 1.32g and the difference between the two was significant. For the late varieties on table 6, dry matter ranged between 0.61g and 1.48g with TGX 1440-1E producing the highest dry matter yield. TGX 1896-3F recorded highest dry matter yield of 0.9g at 0mM/I phosphorus.

Phosphorus concentration in dry matter of early, medium and late varieties of soybean grown in nutrient solution is presented on figures 1, 2 and 3. There was significant difference among the varieties and across the phosphorus levels for all the varieties used for the study. The interactions for all maturity groups were also significant.

In the early varieties (Fig 1), TGX 1895-49E had the highest P concentration of 7.38ppm followed by TGX 1985-19F and the difference between them was significant while TGX 1892-10F had the least P concentration of 4.45ppm in its dry matter at 2.0mM/l P level. TGX 1895-49E also produced the highest P concentration at 0mM/l P level.

Among the medium varieties (Fig 2) TGX 1893-10F had the highest P concentration of 25ppm followed by TGX 1891-3F with 24.50ppm while TGX 1878-7E had the least P concentration. The highest P concentration 15.50ppm was recorded by TGX 1019-2EN, at the 0mM/l P level

The effect of P treatment on P concentration for the late soybean varieties is presented on Figure 3 with TGX 1440-1E recording the highest P concentration of 12.50ppm followed by TGX 1844-18E and TGX 1869-13E with 12.00ppm at 2.0mM/l and there was

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significance between these values. The lowest P concentration at 2.0mM/l of 6.53ppm was recorded by TGX 1866-7F. TGX 1869-13E had the highest P concentration of 8.17ppm at 0mM/l.

Efficiency index (EI) calculated for each variety is presented on Table 9. Efficiency parameters used were dry matter (shoot and root) yield, P- concentration in dry matter and efficiency index.

The efficiency index is the ratio of the dry matter to the total phosphorus concentration in the dry matter. The values varied between 6.14 and 37.13 with TGX 1842-1E having the highest and TGX 923-2E with the lowest EI. The former is a medium variety while the latter is a late variety. Varieties with high efficiency index also had high dry matter yield.

Table 1: Mean Squares Estimates for Shoot Length and other Yield Attributes for Eight Early Soybean Varieties Grown In Hydroponics

Sov. Df Shoot length Root length Leaf No. Dry Matter

P Conc in Dry Matter

Rep Var. Error(a) Phoslev Var. x phoslev Error(b)

2 7 14 3 21 48

10.39 159.90* 23.39 521.46* 73.93* 17.43

13.17 74.92* 8.14 332.18* 25.78* 7.05

12.67 6.27* 1.64 52.68* 4.99* 1.34

0.06 0.14* 0.04 0.28* 0.03* 0.01

0.01 6.49* 0.002 13.26* 0.41* 0.001

CV% 9.57 12.74 13.74 8.03 0.82

* = Significance at 5% probability Table 2: Mean Squares Estimates For Shoot Length and other Yield Attributes for Seventeen medium Soybean Varieties Grown In Hydroponics

Sov. Df Shoot length

Root length

Leaf No. Dry Matter P Conc in Dry Matter

Rep Var. Error(a) Phoslev Var. x phoslev Error(b)

2 16 32 3 48 102

81.18 455.32* 14.97 336.11* 32.60* 16.27

42.14 89.19* 8.73 116.50* 25.39* 12.13

48.65 16.02* 0.74 18.68* 3.15* 1.29

0.01 0.25* 0.04 0.44* 0.07* 0.02

0.005 25.68* 0.001

121.13* 3.53* 0.001

CV% 9.91 17.69 15.39 14.41 0.31

* = Significance at 5% probability Table 3: Mean Squares Estimates For Shoot Length and other Yield Attributes for Twelve Late Soybean Varieties Grown In Hydroponics

Sov. Df Shoot length

Root length

Leaf No. Dry Matter

P Conc in Dry Matter

Rep Var. Error(a) Phoslev Var. x phoslev Error(b)

2 11 22 3 33 72

127.75 377.46* 19.37 635.06* 18.24ns 14.49

64.77 105.80* 10.13 301.14* 27.19* 9.76

32.13 11.64* 1.05 37.73* 1.99ns 1.66

0.06 13.40* 0.70 34.99* 4.27* 0.60

0.001 32.73* 0.0002 102.68* 1.81*

0.0003

CV% 9.24 12.25 15.23 9.15 0.22

Ns = Not Significant

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* = Significance at P≤ 0.05 Table 4: Effect of P treatments on dry Matter Weight (g) for Eight Early Soybean Varieties Grown in Nutrient Solution.

P treatment in the nutrient solution (mMol/I)

Variety 0 0.5 1.0 2.0 TGX1485 -1D 0.63 0.78 0.80 0.97 TGX1830-20E 1.00 1.07 1.08 1.13 TGX1835-10E 0.92 0.98 1.05 1.07 TGX1832-32E 0.87 0.90 1.03 1.13 TGX1895-23E 080 0.92 1.12 1.33 TGX1892-10F 1.02 1.17 1.22 1.35 TGX1895-19F 0.90 0.95 0.98 1.15 TGX1895-49E 0.92 0.93 1.05 1.27 LSD at 5% probability var. = 0.07 P Level = 0.05 V x P = 0.14 CV% = 8.03 Table 5: Effect of P treatments on dry Matter Weight (g) for Seventeen Medium Soybean Varieties Grown in Nutrient Solution.

P treatment in the nutrient solution (mMol/I) Variety 0 0.5 1.0 2.0 TGX1805-31F 0.68 0.78 0.92 0.98 TGX1019-2EN 0.65 0.68 0.80 0.80 TGX1890-7F 0.81 0.83 0.98 0.99 TGX1802-1F 0.82 0.83 0.85 1.22 TGX1880-3F 0.61 0.70 0.75 0.82 TGX1891-3F 0.78 0.87 0.95 1.23 TGX1893-10F 0.78 0.95 1.07 1.18 TGX1842-1E 0.85 0.88 1.03 1.93 TGX1838-5E 1.00 1.06 1.20 1.30 TGX1893-6F 0.80 0.85 0.90 1.21 TGX1888-15F 0.70 0.76 0.85 0.93 TGX1873-16E 0.64 0.70 0.75 0.80 TGX1802- 13F 0.61 0.65 0.65 0.70 TGX1878-7E 0.90 0.93 0.90 1.08 TGX1893-7F 0.96 1.00 1.11 1.22 TGX1894-3F 0.77 0.91 1.25 1.53 TGX1882-2F 0.77 0.90 1.25 1.32 LSD at 5% probability var. = 0.11 P Level = 0.05 V x P = 0.20 CV% = 14.41

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Table 6: Effect of P treatments on dry Matter Weight (g) for Twelve Late Soybean Varieties Grown in Nutrient Solution.

P treatment in the nutrient solution (mMol/I) Variety 0 0.5 1.0 2.0 TGX1896-3F 0.90 0.93 1.20 1.30 TGX1866-7F 0.80 0.81 0.86 0.91 TGX1895-35F 0.78 0.79 0.82 0.84 TGX923-2E 069 0.78 0.87 1.12 TGX1869-13E 0.80 0.87 0.90 1.12 TGX1844-18E 0.61 0.66 0.72 0.93 TGX1886-38D 0.70 0.73 0.76 0.78 TGX1440-1E 0.70 0.83 0.88 1.48 TGX1844-4E 0.83 0.89 0.90 1.07 TGX1448-2E 0.68 0.68 0.78 0.85 TGX1864-17E 0.68 0.81 0.86 0.95 TGX1889-12F 0.75 0.83 0.90 0.93 LSD at 5% probability var. = 0.06 P Level = 0.04 V x P = 0.11 CV% = 9.15 Table 7: Efficiency Index and dry Matter of Thirty-seven Soybean Varieties Grown in Nutrient Solution at Lowest P Level.

VAR. DM EI VAR. DM EI

TGX1485-1D TGX1830-20E TGX1835-10E TGX1831-32E TGX1895-23E TGX1892-10F TGX1895-19F TGX1895-29E TGX1805-31F TGX1888-15F TGX1873-16E TGX1802-3F TGX1878-7E TGX1893-7F TGX1894-3F TGX1882-2F TGX1019-2EN TGX1890-7F TGX1802-1F

6.30 10.00 9.20 8.70 8.00 10.20 9.00 9.20 6.80 7.70 6.40 6.10 9.00 9.60 7.70 7.70 6.50 8.10 8.20

20.65 32.64 34.57 28.57 18.29 22.24 20.25 19.55 10.05 11.11 8.43 11.10 33.06 33.30 16.56 18.71 10.88 23.09 17.24

TGX1880-3E TGX1891-3F TGX1893-10F TGX1842-1E TGX1838-5E TGX1893-6F TGX1896-3F TGX1869-13E TGX1844-18E TGX1886-38F TGX1440-1E TGX1844-4E TGX1448-2E TGX1864-17F TGX1889-12F TGX1866-7F TGX1895-35F TGX923-2E

6.10 7.80 12.30 11.80 10.00 8.00 9.00 8.10 6.10 7.00 8.80 9.10 7.80 6.80 9.00 8.30 7.50 6.90

13.35 17.92 26.68 37.13 23.98 19.51 24.00 8.04 7.41 9.80 11.06 11.42 8.11 10.75 17.61 23.50 20.00 6.14

DM = Dry Matter VAR=Variety

EI = Efficiency Index

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Figure 1: Effect of 0, 0.5, 1.0 and 2.0 mM/ treatment on P concentration in

dry matter of eight early soybean varieties.

l

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Fig

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Fig

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2.0 mM

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DISCUSSION

There was variability among the soybean varieties in their response to phosphorus uptake and use

efficiency. As application of phosphorus increased the yield components of the varieties used also increased. This agreed with Safwat, et. al. (1994), where shoot dry weight and root development was better with increased phosphorus application. Other

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earlier works, Barber (1977), Parihar and Tripathi (1989) and Pundarikakshudu (1989) also collaborate these results.

Efficiency parameters used were dry matter yield (shoot, and root), P- concentration in dry matter and efficiency index which was used to classify the thirty seven soybean varieties. Dry matter (DM) increased with increased application of P and in the early varieties, TGX 1892-10F had the highest DM at lowest and highest P application but this was not the case with other varieties where some performed well at low P application but could not keep the performance up with increase P application. This must have been as a result of difference in their genetic composition.

P-concentration in plant tissue also increased with increased phosphorus application and this was also reported by Pal, et. al. (1989) and Furlani (2002) that P- concentration in leaves of soybean were lower in plants not supplied with P fertilizer.

Efficiency index (EI) which evaluates the amount of dry matter produced for a given P- concentration in the plant tissue was calculated for each variety. It is the ratio of the dry matter accumulated at the lowest P level to the total P contained in the dry matter. Some EI decreased with increased level of P while others varied from one P level to another. Evidence from studies by Fulani, et. al. (1998) suggested that maximum efficiency index is usually found in low P level. There was variability among the varieties for EI determined at the lowest P level. Five varieties, TGX 1830-20E, TGX1835-10E, TGX 1878-7E, TGX 1893-7F and TGX 1842-IE had very high EI of more than 30. The efficiency index was used to classify the thirty seven soybean varieties into four classes. The varieties were plotted comparing the p-efficiency index in the lowest P-level in the Y-axis against the proportional increase in dry matter yield (DMmax/DMmin) obtained for each variety in the X-axis. The average values for the means in the X and Y-axis defined the four classes thus:- efficient – responsive (ER), efficient non-responsive (ENR), inefficient responsive (IR) and inefficient non-responsive (INR). Those considered to be efficient had P-efficiency index above average for the lowest P-level and responsive those that had high dry matter yields above the average value at the lowest P-level while the inefficient varieties had low EI and non-responsive low dry matter below the average value. Sixteen varieties TGX 1830-20E, TGX1835-10E, TGX1831-32E,TGX 1892-10F, TGX 1895-19F, TGX 1895-49E,

TGX 1878-7E, TGX 1893-7F, TGX 1882-2F, TGX 1890-7E TGX 1893-10F, TGX 1891-3F, TGX 1842-1E, TGX 1838-5E, TGX 1896-3F, TGX 1889-12F. were efficient and responsive, five varieties TGX 1485-1D, TGX 1895-23E, TGX 1893-6F,TGX 1866-7E, TGX 1895-35F.were efficient non –responsive, two varieties TGX 1440-1E, TGX 1844-4E were inefficient responsive and fourteen TGX 1805-31F, TGX 1888-15F, TGX 1873-16E, TGX 1802-3F, TGX 1894-3F, TGX 1019-2EN TGX 1802-1F, TGX 1880-3E, TGX 1869-13E, TGX 1844-18E, TGX 1886-38F, TGX 1448-2E, TGX 1864-17F, TGX 923-2E were inefficient non-responsive. All early varieties were efficient and responsive except TGX 1485-1D which though efficient was non-responsive as the plant produced dry matter below average.

Differences among soybean varieties with respect to efficiency in P-uptake and use were evident in this experiment in view of the great magnitude of variability for P-uptake and use in the varieties used, those observed to be efficient could be planted and high yield expected in soils that are deficient in phosphorus.

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