Pigeon pea Cajanus cajan (L.) Millsp.

Climate

Pigeonpea is predominantly a crop of tropical areas mainly cultivated in semi-arid regions of India. Pigeonpea can be grown between 14°N and 28°N latitude, with a temperature ranging from 26° to 30°C in the rainy season (June to October) and 17° to 22°C in the postrainy (November to March) season. The amount of daily global solar radiation varies from 400 to 430 cal cm day in the rainy season and 380-430 cal cm-2 day-1 in the postrainy season. Mean annual rainfall ranges from 600 to 1400 mm, of which 80%-90% is received in the rainy season. The length of growing season extends from 120 to 180 days. Isoclimes similar to India exist in western Africa and southern Sudan, a suitable environment for growing pigeonpea. Pigeonpea is very sensitive to low radiation at pod development, therefore flowering during the monsoon and cloudy weather, leads to poor pod formation.

Soils

In India, pigeonpea is cultivated on Entisols, Alfisols, Enceptisols, and Vertisols. The Entisols found in the alluvial- soil belt of the Indo-Gangetic region are deep loams, slightly alkaline (pH 7.5-8.5), with about 150-200 mm available water storage capacity in 2 m of soil. The Vertisols are characterized by 40-60% clay in the surface soil horizons, pH around 8.0 with a water holding capacity between 150-300 mm, and the available water in the top 1.5-2.0 m of soil. Alfisols are neutral in reaction (pH 6.5-7.0) and relatively shallow with a low-clay content. They are often sandy loam and can retain about 100 mm available water in the root profile (Reddy and Virmani 1981). Pigeonpea, being sensitive to water logging, requires a well-drained soil. It does not grow well in saline soil, but can withstand drought reasonably well. Responses to lime indicated by increase in shoot growth and nodulation, have been reported in soils with pH below 5.0 (Edwards 1981).

Varieties

Some of the important varieties of pigeon pea released in India for the different maturity groups.(Tables 5a, 5b, 5c, and 5d).

Table 5a. Extra-short-duration varieties of pigeonpea released in India

Variety	Pedigree	Year of release (State)	Time to maturity (days)	Characteristics
UPAS-120	Selection from P 4758	1976 (UP)	120-140	Nondeterminate, yield 1.5-1.8 t ha
Pant A3	-	1975n (UP)	120-130	Semierrect, determinate, dwarf 3-4 seeds pod
Prabhat	TI X T 190	1975 (UP)	110-120	Determinate, dwarf (100-120 cm) , clustered fruiting, yield 1.2-1.5 t ha
ICPL 87 (Pragati)	T21x JA 277	1986 (Penin. India)	120-130	Determinate, 10.5 g (100 seed) brown seeded, potential yield 2.5-3.0 t ha
ICPL 151 (Jagriti)	ICP 6997 x Prabhat	1990 (NW  India)	120-130	Determinate, 10.5 g (100 seed) cream color, potential yield 2.5-3.0 t ha

Table 5b . Short-duration varieties of pigeonpea ralaasad in India.

Variety	Pedigree	Year of release (State)	Time to maturity (days)	Characteristics
Pusa Ageti	Brazil 1-1 x T190	1971	150-160	Dwarf compact plant, determinate, bold seeded 9 g (100 seed) 4-5 seeds pod potential yield 2.5 t ha
T21	TI x T190	1961 (UP)	150-170	Semi-spreading, loose plant and indeterminate branching. Small seeded, 7 g (100 seed)
HY2	PI 4628	1978 (AP)	140-150	Semi-errect tall, purple stem, white seed, bold, 11-12 g (100 seed) potential yield 2.5-2.7 t ha average 1.3-1.9 t ha
Pusa 84	Pusa Ageti x T21	1980 (N zone)	140-150	Medium tall, semi-spreading, 3-4 pod-1, 7.5 g (100 seed) brown seeded.
C01	Local (Tamil Nadu)	1970 (TN)	135-140	Photoinsensitive, brown seeded, 7 g (100 seed)- 1, average yield 1.5 t ha-1.

Table 5c . Medium-duration varieties of pigeonpea developed in India.

Variety	Pedigree	Year of release (State)	Time to maturity (days)	Characteristics
HY 1	PI 3704	1975 (AP)	160-170	Spreading, purple stem, white seed, potential yield1.9-2 t ha average 1.2-1.5 t ha
HY 3A	PI 2817-1A	1980 (AP)	160-170	Erect tall plant (230-240 c m ) , green stem, white bold seeded, 18-20 g potential yield 3.0-4.0 t ha average yield 1.6-2.0 t ha
HY 5	PI 3701	1980 (AP)	160-170	Semi-erect, purple stem, medium height (170 cm ) , brown seeded,
AS 71-37	Local selection	1981 (MP)	165-195	Medium tall (172-194 cm),potential yield 3.0 t ha, ave. 1.65 t ha
BDN 1	Local selection	1978 (Maharashtra)	160-179	Semi-spreading, wilt resistant height (200-220 cm)
S20	Kanke 1XB7	1976 (WB)	180-190	Semi-compact, Potential yield 2.5 t ha average yield 1.7 t ha

Table 5d . Late-duration varieties of pigaonpaa ralaaaad in India.

Variety	Pedigree	Year of release (State)	Time to maturity (days)	Characteristics
C11	Local selection	(AP)	200-220	Medium tall, profuse branching, spreading, brown seed,
Bahar	D1258 X Local	1973 (Bihar)	220-240	Compact, semi-erect plant, brown round selection 4-5 seeds pod- yield potential 3 t ha average yield 2.25 t ha
Laxmi (Kanke-3)	BR-183X Local	1974(WB)	180-220	Perennial, semi-spreading, field tolerant to wilt, potential yield 2 t ha average yield 1.75 t ha
Gwalior 3	Local selection	1960/ 1980 (MP)	270>	Tall 250-300 cm, spreading, light brown seed, 7-8 g (100 seed)

Cropping Systems

A cropping system is defined as a combination of crops in spaceand time. The objective of any given system should be to provide the farmer a high and sustainable level of returns. In agronomic terms , the system makes efficient use of the basic resources necessary for plant growth (Willey etal 1981 ). Pigeon pea is grown both under sole and intercropping systems .

Sole cropping

Early-maturing (100-120 days) genotypes are grown as a sole crop. These genotypes have a higher harvest index with an average of 34 % compared to medium-maturing genotypes at 24 % (Sheldrake and Narayanan 1979 ). Therefore, from the cropping system point of view, early - maturing genotypes are better able to 'complement' by providing an increased opportunity for a second crop (Willey et a l. 1981 ) . Postrainy season pigeonpea are also cultivated as a sole crop. This avoids the wet conditions associated with the rainy season, gives less incidence of pests and d i s eases, and makes better use of residual soil

moisture . Moreover, postrainy season sole crops were found more efficient than the rainy season sole crops (Willey et al . 1981 ) .

Pigeonpea intercropping

Pigeonpea is commonly intercropped with a wide range of crops . In India, it was estimated that 80 % - 90 % of the pigeonpea were  intercropped (Aiyer 1949 ) . Willey eta l. (1981) grouped pigeon pea intercrops into three broad categories:

• a)     With cereals (sorghum, maize , pearl millet, setaria, finger millet , and rainfed rice).
• b)     With legumes (groundnut, cowpea, mung bean, black gram, soybean, and phaseolus bean ) .
• c)     With long-season annuals (caster, cotton, sugarcane, and cassava) .

The advantages of intercrops are (Willey et al. 1981):

• Intercropping confers greater yield stability than sole cropping. For instance, if one crop fails or grows poorly, the other crop can produce to some extent.
• Under stress conditions, intercropping gives less yield depression than sole cropping.
• Intercropping may reduce the incidence of weeds. The poor canopy cover and slow growth of pigeonpea in the early stages makes a sole crop susceptible to weed. Therefore, a fast-growing intercrop not -only gives a potential additional yield benefit, but also reduces the need for weeding (Shetty and Rao 1979).

Land Preparation

Land preparation for pigeonpea requires at least one ploughing during the dry season followed by 2 or 3 harrowings. The "summer" plowing helps in minimizing the weed flora and to conserve moisture (Chandra et al. 1983). Well-drained soils are necessary for good root and nodule development. Contour beds or a ridge-and-furrow system are useful in preventing water logging by draining excess surface water,and in preventing soil erosion. Organic manure may be applied 2-4 weeks before sowing. In acidic soils 2-4 t ha-1 of lime is incorporated 3-4 weeks before sowing to neutralize the acidity. In light soils, a basal application of aldrin 5% dust @ 30 kg ha-1 prevents termite infestation (Chandra et al.1983).

Seed Rate and Seed Treatment

The seeding rate of pigeonpea depends on the desired plant density for a genotype (early, medium or late) , cropping system (pure crop, mixed crop, or inter crop) , germination rate of seed,and mass of seed.

Seed should be own behind the plough or with the help of seed drill at a row spacing of 60-75 cm keeping 15-20 cm distance from plant to plant. A seed rate of 12-15 kg per hectare is sufficient. In mixed cropping seed rate is adjusted according to the proportion of arhar and companion crops to be grown. In the intercropping seed rate remains same as for pure crops.

Good quality and pure seed (registered or certified) of the selected variety should be used from a reliable source. Before sowing, the seed should be treated with thiram @ 1.5 g kg- 1 of seed plus penta - chloro - nitro benzene (PCNB) [Brassicol® a.i.1.5 g kg- 1] seed. This w i l l avoid seed rot and seedling blight diseases (Chandra et.al . 1983). At ICRISAT we recommend seed treatment with 3 g thiram kg-1 + 3 g carbendazim kg-1 seed.

Sowing Time

In the rainfed and dry areas pigeon pea are sown with the onset of the monsoon. Earlier sowing gives higher yields in India. When sowing extra - early and early - maturing varieties in the 1^st fortnight of June , the field is available for post rainy season crops by the end of November. Therefore , sowing should not be delayed beyond June.

The sowing of medium and late-maturing varieties , under rainfed conditions , should be d o n e during June or July at the onset of the monsoon. This should be preferably before the 2^nd week of July. Late sowing causes considerable reduction in yield due to photoperiodicity and excessive soil moisture stress which coincides with the reproductive growth (Chandra et al. 1983). The postrainy season sowing in India should be done in September. In sowings later than 15 October , yields drastically decline (Narayanan and Sheldrake 1979).

Methods of Sowing

Three systems of sowings are practiced for pigeon pea. The common is flat sowing, the other methods are broadbed-and-furrow for extra-early group and ridge-and-furrow for the late maturity group. The latter two methods are useful in fields with poor surface drainage and water logging. The raised beds or ridges also provide better aeration and nodulation in comparison to the flat sown crop. Experiments at the Indian Agricultural Research Institute, New Delhi, have shown that pigeonpea sown on a ridge-and-furrow system in fields prone to water logging gave 30 % more yield compared to flat sowing (IARI 1971). At ICRISAT a broad bed and furrow system is used for sowing extra-early genotypes, and ridges-and-furrows are used for medium and late  duration genotyes.

Responses to Nutrients

Responses to general fertilizer applications in pigeonpea are quite meager.

Nitrogen (N): Kulkarni and Panwar (1981) reviewed the studies in India on the pigeonpea response to N. They concluded the effect was almost negligible. However, in some situations a starter application of 20-25 kg N ha-1 was beneficial.

Phosphorus (P): Responses to phosphorus applications have been positive and in some cases highly significant in pigeonpea (Pathak 1970). Kulkarni and Panwar (1981) summarized the phosphorus response studies in India.

They concluded that applications of 17-26 kg P ha-1 increased seed yield by 300-600 kg ha-1. Responses of pigeonpea to P fertilization would not be expected in soils with more than 5 mg kg-1 extractable P by Olsens bicarbonate extraction; although lower values would not necessarily predict a response (Johansen 1990).

Potassium (K): Pigeonpea does not respond to potassium chloride applications unless it is grown on low available potassium soils (Kulkarni and Panwar 1981).

Rhizobium inoculation: Responses to Rhizobium inoculation have been inconsistent (Panwar and Misra 1973; Panwar 1975). Increases in grain yield of pigeonpea inoculated with effective Rhizobium ranged from 19 to 68% (Kumar Rao 1990).

Zinc (Zn): Most of the pigeonpea cultivars are susceptible to zinc deficiency. Therefore, foliar applications of 2-4 ppm zinc as 0.5% zinc sulfate with 0.25% lime have been effective to over-come zinc deficiencies

(Saxena and Singh 1970).

Irrigation

Pigeonpea is largely grown as a rainfed crop, however, it is well established that flower initiation and pod setting stages are the most crucial to drought stress . Therefore, irrigation at these stages usually helps the crop (Chandra et al. 1983). The drought-stress symptoms on pigeon pea are indicated by the leaves pointing towards the sun at noon (Chauhan et al. 1988).

Excessive moisture is detrimental to pigeon pea. It promotes vegetative growth and enhances the incidence of Phytophthora and Alternaria blight. Therefore , irrigation should be given only when the crop experiences drought stress after flowering and at the pod filling stage (Chandra et al. 1983). Responses to irrigation are more consistent in postrainy season sown pigeon pea. This crop relies on moisture stored in

the soil profile. Two or three irrigations, 1 mont h after    sowing, increased seed yield by about 150-160% over the nonirrigated control at ICRISAT Center (Rao et a l . 1 9 8 3 )  

Weed Management

Pigeonpea is a slow-growing crop and mostly cultivated during the rainy season. The crop suffers from early we e d infestation. Therefore, it is necessary to keep the crop weed-free during the early growth period (4-6 weeks ). The weeds can be controlled mechanically or with chemicals. A combination of chemical and mechanical control is more economical . At ICRISAT Center, it was observed that a pre emergence application of prometryn (Gesgard® or Caparol® a.i. 1.25 kg ha- 1) effectively controlled the initial weeds .

A hand weeding 3-4 week after sowing is required to remove the late emerging weeds . When herbicide is not applied, two or three hand weedings are required from the 1st to 6th week of crop growth. Later the crop will be able to smother t h e weeds (Chauhan et al. 1988). At ICRISAT, hand weedings were always found superior to herbicides , but the herbicides were more economical , hence preferred (Chauhan 1990). The other pre emergence herbicides effective for pigeonpe a are pendimethalin (Stomp® a.i. 1.0-1.5 kg ha- 1) or meta chlore (Dual® a.i. 1 kg ha-1). The post emergence herbicides recommended are flausifop-P butyl (Fusilate® a.i. 0.2-0.4 kg ha-1) or bentazon (Basagran® a.i. 1.0 kg ha- 1) at 2-4 leaf stage (A. Ramakrishna, 1992,  ICRISAT, personal communication).

Diseases

Wilt: the most serious is wilt disease (Fusarium udum), favored by soil temperatures of 17°-20°C. The fungus enters the plant through the roots and may persist in soilborne stubble for a long time. The leaves of the affected plants become yellowish in colour, then drop and finally the whole plants dry out. The disease , in fact, can be diagnosed by seeing the black streaks on the wood after removing the outer epidermal strip from the major roots.

Control measure

• The only effective control measure is development of resistant cvs (e.g., 'C-ll, C-36, NP-15, NP-38, aT-17'Amar, Azad, Asha, Maruthi, BDN-1, BDN-2,NP-5).
• Rotation with tobacco and intercropping with sorghum is said to decrease the wilt problem.