Mungbean (Vigna radiata L. Wilczek) is an important grain legume. Among the pulses in Bangladesh, mungbean ranks fifth in acreage and production, and first in market price (BBS, 1999). It is an excellent source of vegetable protein which contains about 21-25% protein (Afzal et al., 1998).
In Bangladesh, it is traditionally used as whole or split seeds as Dhal (soup) but in some other countries of the world sprouted seeds are used as vegetables. In addition, it also improves the fertility status of the soil through nodulation.
Mungbean is generally grown on marginal lands of poor fertility and low moisture status and under poor management conditions. In other words, due to the competition with high yielding variety (HYV) of cereals such as rice, wheat etc. in terms of production and economic returns, and are thus being pushed to the marginal lands where nutrient limitations are severe. That is why, the acreage and production of mungbean are decreasing day by day (BBS, 1999). Under this situation, proper nutrient management and use of modern variety may be practiced. Application of fertilizers improves the plant productivity and enhanced the seed yield compared with the farmers' practices (Sarma and Sarma, 1999). Adreshna et al. (1993) also reported that Rhizobium inoculation significantly increased the seed yield, and the increase was 9.6% more compared with no inoculation. Therefore, an experiment was undertaken to determine the fertilizer requirements for mungbean in increasing the seed yield to a considerable extent.
Materials and Methods
The experiment was carried out at the Regional Agricultural Research Station of Barisal, Bangladesh in the Kharif season of the year 2000. The experimental site belongs to the Non-Calcareous Grey Floodplain soils under Agroecological Zone-13 (Anonymous, 1988). The experimental field was medium high land with clay loam textured soil having a pH value of 6.8. Characteristically, the soil contains 2.15% organic matter, 1.47% organic carbon, 0.23% total nitrogen, 23.87 Fg/g soil available phosphorus, 41.84 Fg/g soil available sulphur and 0.55% meq/100 g soil exchangeable potassium.
Following experimental treatments were applied:
A. Mungbean variety: Barimung-4
B. Fertilizer combinations (kg ha1)
||Rhizobium + P40K20
||Rhizobium alone, and
The experiment was laid out in a randomized complete block design with three replications. The unit plot size was 4 x 3m2. Plot to plot distance was 1m, and each plot was separated from another by 25 cm wide ridges and 50 cm wide furrows. Previously, the experimental land was opened with a tractor drawn disc plough. Later on, the land was ploughed and cross-ploughed three times by country plough followed by laddering to obtain a desirable tilth. All the weeds and stubbles were removed and the land was made ready.
After layout preparation, the unit plots were fertilized as per the experimental specifications. Nitrogen, phosphorus and potassium were applied in the form of urea, triple super phosphate and muriate of potash, respectively. On the other hand, seeds were inoculated with Rhizobium just before sowing. All the fertilizers were incorporated into the soil before seed sowing.
The seeds of Barimung-4 were sown following line sowing method. The line to line and plant to plant distances were 30 and 10 cm, respectively. The sowing depth was maintained at about 3 cm from the soil surface. The intercultural operations were done as and when required.
The crop was first harvested when about 80% pods of the plants became mature and the pods were collected by hand plucking from the plants of the individual plots and kept separately with proper tagging. After proper sun drying, the seeds were separated from the pods and further the seeds were dried maintaining about 8-10% moisture level. The rest of the pods were harvested after maturity, and drying and threshing were done following the procedure described above.
Data on different plant characters such as plant height, branches/plant, pods/plant, pod length, seeds/pod, were recorded carefully from the randomly selected 10 plants of each plot. Thousand seeds were also randomly selected from each plot and weighed. The seed and straw yields were taken plot wise and converted into kg ha1. All the collected data were analyzed statistically and the means were separated by Duncan's Multiple Range Test using the computer package MSTAT.
Results and Discussion
All the plant characters studied in present study viz., branches/plant, plant height, pods/plant, pod length, seeds/pod, 1000-seed weight, seed and straw yields, and harvest index significantly influenced due to the application of various combinations of NPK fertilizers and Rhizobium inoculation (Table 1). The results of the present experiment are presented and interpreted under following headings:
Seed yield: The munghean variety produced the maximum seed yield (1270.21 kg ha1) when the crop was fertilized with N20P40K20 kg ha1 (Table 1). This result was similar to the findings reported by Dhingra et al. (1998), they noted that the highest productivity of mungbean was obtained with 30 kg N, 40 kg P and 20 kg K ha1 under the normal plant density. Khanam et al. (1996) also found that the NPK plus compost treatment increased the seed yield of mungbean by 83-87%. On the other hand, Sardana and Verma (1987) carried out a field trial and followed that application of N, P and K fertilizers resulted in significant increases in seed yield of mungbean.
Among the fertilizer combinations, the second highest seed yield (1220.30 kg ha1) was obtained from the plants treated with Rhizobium inoculation + P40K20 kg ha1. The application of N20P40 kg ha1 to mungbean gave the moderate seed yield (1131.68 kg ha1) which was statistically similar with Rhizobium inoculation alone (1123.32 kg ha1) and N20 K20 kg ha1 (1106.67 kg ha1). The lowest seed yield (887.01 kg ha1) was produced from the control condition where no fertilizer or Rhizobium inoculation was applied (Table 1).
Straw yield: The maximum straw yield (2434.36 kg ha1) was received from the plants fertilized with N20P40 K20 kg ha1 showing statistically identical variation with the application of Rhizobium inoculation + P40 K20 kg ha1 (2406.14 kg ha1). Partially similar trends were also observed by Sarkar and Banik (1991) that the interaction effects between N and P on straw yield of mungbean was significant with higher rates of both N and P, these were corresponding higher straw yield. The lowest straw yield (1864.68 kg ha1) was obtained from the control (Table 1).
The yield components such as pods/plant, pod/length, seeds/pod and 1000-seeds weight were found to be the highest (43.00, 6.84 cm, 12.11 and 32.08 g respectively) from the crops fertilized with N20P40K20 kg ha1.
|Table 1:||Effects of NPK fertilizers and Rhizobium inoculation on the plant characteristics and yields of mungbean
|In a column, the figures having common letter(s) do not differ at 1% level|
The longest plant (48.63 cm), maximum number of branches/plant (6.28) and maximum harvest index (34.29%) were obtained by the application of N20P40K20 kg ha1, and the parameters namely plant height and number of branches/plant were statistically at par with the fertilizer combination, Rhizobium + P40 K20 kg ha1.