Climatic Requirements of Pulses
Postrainy-season Pulses: The major postrainy-season pulses are khesah, lentil, and chickpea. The temperature optima for the growth of postrainy-season pulses lie between 10°C and 30°C (Saxena 1979). On this consideration, 110-115 days are available for growing postrainy-season pulses. For the short and mild winter conditions of Bangladesh, cultural management should be designed to fully exploit the available growing period.
Rainy-season Pulses
These pulses include black gram, mung bean, and pigeon pea (Cajanus cajan (L.) Millsp.) The optimal temperature for growth and development of most summer pulses is between 25°C and 35°C. They can tolerate high temperatures up to 40°C but are sensitive to low temperatures (below 18°C). These crops are normally drought tolerant but sensitive to waterlogging. M u n g bean and black gram, grown during the summer, are daylength insensitive. However, a daylength sensitive mung bean cultivar locally k n o w n as Sonamoong is grown in certain specific locations during the postrainy season. Summer pulses can be grown almost throughout the year except during the short winter season.
The Role of Pulses in Cropping Systems: All the major cropping patterns are rice-based. Therefore, postrainy-season pulses have to compete with boro (winter) rice and wheat, particularly in regions where irrigation facilities are available. In areas where lentils and chickpea are sown after the harvest of Aman (rainy-season) rice (August-December) growth and yield are affected adversely. In the early monsoon (Kharif I) season (March-May) uncertain and erratic rainfall restricts the cultivation of summer pulses. In the late monsoon season (Kharif II) (August-October), mung bean and black gram have the potential to follow Aus (rainfed) rice or jute (April-July), particularly in the northern districts. In the southern districts, mung bean may follow Aman rice and precede Aus rice. Temperatures during the late monsoon are sufficiently high to support the growth of summer mung beans.
Research Studies
Effect of Date of Sowing and Seeding Rate on Chickpea and Lentil Pulses like lentil and chickpea is grown in the dry winter months under rainfed conditions. As the climate imposes a restriction on the duration of growth of lentils and chickpea (approximately 110 days), timely sowing is important in order to exploit the residual soil moisture and to bring the crop to maturity. Experiments conducted on the combined time of sowing and seeding rate with lentil cultivar Pabna local and chickpea cultivars Nabin and Sabur 4 over the years at various locations in Bangladesh underline the importance of timely sowing. Irrespective of the seeding rates used (20-40 kg ha-1), the optimum date of sowing for lentils at Ishurdi and Jessore, appeared to be between the third week of October and the third week of November. At Joydebpur, where late October sowing was not possible due to excess soil moisture, the optimum date was between the first and third week of November. For chickpeas, the optimum time of sowing appeared to be between the third week of October and the middle of November. Late sowings (December) significantly reduced grain yields as high temperatures during the pod setting and grain filling stages reduced the grain-filling period and days to maturity ( BARI 1985). A survey carried out in farmers' fields in Natore and Faridpur districts (results not presented here), also corroborated the experiment station results. Irrespective of seeding rates used by the farmers, significantly higher chickpea yields were obtained from the crop sown in November (compared to the later-sown crop).
Yield Response of Lentil and Chickpea Under Different Management Practices Experiments were conducted to determine whether lentil and chickpea yields could be improved through better management practices. The effect of different levels of management on lentils was evaluated at Jamalpur during 1984/85. Conventional tillage (as practiced by the farmers) coupled with one hand weeding at 3 weeks produced a higher yield (1000 kg ha-1) than that produced by minimum tillage. Additional benefits from hand weeding are possible only with conventional tilling. With minimum tillage, hand weeding and fertilizer use produced higher yields only when combined. In chickpea Nabin irrigation and fertilizer application failed to elicit any response in terms of yield at Ishurdi and Jessore. Moreover, fertilizer application and drilling seed in the moist zone had no effect on chickpea yields. These results show that presently available cultivars of chickpea and lentils do not respond to better management practices.
Crop Management in Mung Bean: Experiments on the effect of plant population and weed-control measures reveal the importance of sufficient plant stand on the yield of mung bean (Hamid et al. 1988). One hand weeding carried out between 10 and 20 D A E (days after emergence) under the highest population density (500 000 plants ha-1) gave the best individual crop yield. An experiment conducted to determine the response of mung beans to different cultural practices revealed the importance of fertilizer application (20-40-30 N-P2O5 - K2O) and hand weeding in minimum-tilled plots. The highest cost-benefit ratio (CBR) and marginal rate of return (MRR) were also obtained from this treatment. Results showed that fanners unable to invest in other inputs may suitably opt for minimum tillage instead of conventional tillage. Possibilities of growing mung bean and black gram under minimum-tillage conditions during the late monsoon have been discussed by Aziz and Rahman (1990).