Indian J. Plant Physiol, VI XXXi, No.1, pp 6-it. (March 1989)
DRY MATTER PRODUCTION, LEAF AREA INDEX AND GROWTJ-' RATES OF SHORT AND LONG DURATION INTERCROPS
V. BALA SUBRAMANIAN AND S. VENKATESWARLU
Division of Crop Science
Central Research Institute for Dryland Agriculture Santhoshnagar, Hyderabad-500 659
(Received Feb. 28, 1989)
SUMMARY
Five rainfed crops as sole and inter crops (sorghum+pigeonpea, pigeonpea+black gram and castor+c1uster bean) were compared on the basis of growth analysis for understanding the basis for variation in responses amongst crops to intercropping. In~ercropping decreased dry matter production, leaf area index, crop growth rate and leaf growth rate of all the crops, but delayed leaf senescence in sorghum and pigeonpea during seed (POd) fitling. Growth rates of reproductive organs and net assimilation rates were lower in intercrops than in sole crops of the early component crops (sorghum, black gram and cluster bean) throughout seed (pod) filling phase, but the growth rates of only earlier formed pods/spikes were affected in the late component crops (pigeonpea and castor).
INTRODUCTION
Effect of intercropping on economic yield of component crops vary depending on kind of crops and crop combinations of intercrop systems (Ofori and Stern, 1987). Even cultivars within a crop differ in their productivity under intercropping (Ntare,1989). Studies on growth responses of different ClOpS under intercopping will possibly help minimise yield reduction in component crops and improve yield advantages of such system. With this objective, intercropping effects on dry matter production, leaf area index and growth rates of crop, leaf and reproductive part of early component (sorghum, black gram and cluster bean) and late compo nent (pigeonpea and castor) crops, grown in the same agro-macro climatic environ ment, were investigated.
MATERIALS AND METHODS
Sorghum (Sorghum bicolor (L.) Moench) cv. CSH. 6, pigeonpea (Cajanus cajan (L.) Mill) cv. HY. 2, black gram (Vigna mungo (L.) Hepper) cv. T. 9, castor (Ricinus
7
GllOWTH ANALYSIS OF lNTEIlCllOPScv. Pusa Navbahar were grown under rainfed conditions in Alfisols as sole and intercrops in randomized block design with four replications in 1986 and 1987. The crops were seeded with the onset of rains in June. The intercrop systems were (1) sorghum+pigeonpea in the row ratio of 2 : 1 (45 em apart) (2) pigeonpea+black gram in the row ratio of I : 2 (30 em apart) and (3) castor+cluster bean in the row ratio of I : 1 (45 cm apart). In these intercrop systems, sorghum, black gram and cluster bean were the early component crops. Plant densities of sorghum (150000), pigeopea (45 0(0), black gram (300000), castor (45000) and cluster bean (200 003) were in the optimum range and similar for each crop under sole and intercropping conditions. Recommended fertilizer doses of 40 kg N and 30 kg P for sorghum, 10 kg Nand 30 kg P for pigeonpea, black gram and cluster bean, and 50 kg Nand 30 kg P for castor were applied. Crops were protected from pests and diseases.
Data on dry matter, leaf area, photosynthetically active radiation (PAR) inter ception, crop growth rate, leaf growth rate and reproductive organ growth rate and net assimilation rate were computed. Statistical significance was inferred from analysis of dry matter and Jeaf area index data, using t test.
RESULTS AND DISCUSSION
Dry matter and leaf area index (LAI) of intercrops were lower than those of sole crops (Table I). Intercropping causes decrease in shoot dry matter and leaf area index of component crops of other systems as well (Ofori and Stern, 1987 ; Tsay et al., 1987). In pigeonpea, the difference between sole and intercrops was not apparent at three weeks after seeding due to slow growth.
Within a month after seeding, competition for light, water and nutrients between two crop rows was unlikely. Soil moisture profile did not vary for sole and intercrops. For instance a month after seeding the soil moisture per cent were 4.5,7.4, and 10.2; :md 5.7, 8.3, and 9.9 for sole and intercrops of sorghum at 0-15, 16-30 and 31-45 em depth respectively. Shackel and Hall (1984) also found that total quantities and patterns of soil water depletion were similar for sorghum and cowpea as sole and intercrops.
8 V. DALA SUBRAMANIAN et
ar
Table I. Dry matter, and leaf area index of five rainfed ClOpS under sole and intercropping conditions
Crops and cropping Shot dry matter (gm-.)* Leaf area index* environment
Vegetative At flowering+ At flowering+ Maximum++ (3 weeks)
Sorghum
Sole 7.9 375 1.78 2.23
Inter 4.0 214 1.34 1.62
Pigeonpea
Sole 1.0 83 1.84 1.84
Inter (
+
Sorghum) 1.0 47 0.56 0.58Inter (
+
Black gram) 1.1 87 1.10 1.12Black gram
Sole '3.8 17 0.17 0.51
Inter 2.2 10 0.Q7 0.32
Castor
Sole 2.8 63 0.61 129
Inter 1.5 40 0.32 0.69
Cluster bean
Sole 1.9 13 0.05 0.34
Inter 1.3 7 0.03 0.14
*
Based on t test (p=O.05) values for intercrops are significantly less than those of respective sole crops, except for pigeon pea at vegetative stage.+ About a month after seeding in black gram and cluster bean, about 2 months lifter seeding in sorghum and castor and about 3 months after seeding in pigeongea.
++ About 55 days after seeding in sorghum, about 2 months after seeding in black gram and . c1ustor bean and about 4 months after seeding in pigeonpea and castor.
dry matter accumulation was more sensitive to intercropping than was LAI in sorghum but LAI was more sensitive than dry matter accumulation in pigeonpea, black gram and castor.
GROWTH ANALYSIS OF INTERCItOP
-.
th:1n'of pigeonpea. Galway et al., (1984) reported that sorghum yield in sorghum+ cowpea system was positively associated with characters related to light (PAR) interception. Light interception was more in the other two interclOp systems than in the respective sole crop canopies, obviously due to presence of early component crops in between the rows of late component crops. The results show that amount
Table II. Growth rates during the respective reproductive stages of five rainfed crops under sole and intercropping conditions
Crops and cropping environment
Crop growth rate·
Leaf growth rate·
Panicle, pod or spike growth
rate·
Net assimilation rate"
Early stage+
Late stage++
Sorghum
Sole 12.3 -1.1 11.1 8.2 9.5
Inter 4.4 -0.4 5.5 4.2 4.4
Pigeon pea
Sole 6.9 -0.1 2.4 1.0 3.9
Inter (+Sorghum) 1.9 0.1 0.2 1.6 3.9
Inter (Black gram) 4.2 0.3 1.4 1.1 3.8
Black gram
Sole 2.8 0.8 2.2 0.8 9.7
Inter 0.9 0.6 1.3 0.5 4.6
Castor
Sole 6.8 3.0 2.9 1.0 8.2
Inter 5.3 2.1 2.1 0.2 9.0
Cluster bean
Sole 2.6 1.4 0.9 0.9 10.7
Inter 1.0 0.6 0.4 0.4 9.2
• g m-I day-l ; •• g m - I (Leaf area) day-I; for each crop, the primary data dry ~matter and
leaf area index) of sole and inter crops were statistically analysed, <and were found significantly different (P=0.05) by employing t test.
+ During the first two weeks from anthesis in sorghum, the primary spike growth in castor and the first month from flowering in the three legume crops. CGR, LGR and NAR pertain to this period.
10
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V. BALASUBRAMANIAN et al
of light interception depends up on the canopy development of component crops, but their spatial arrangement in a system can increase the interception. PAR transmission was highly related to the distribution of leaf area (Tsay et aI, 1987).
Crop growth rate (CGR) and leaf growth rate (LGR) were lower under intercropping than under sole cropping (Table II). In pigeonpea and castor, the CGRs of the intercrops were lower than that of their respective sole crops during seed filling, in spite of being that only component crop of the system still in the field. The CGR of pigeonpea intercropped with sorghum was more affected than when intercropped with black gram. Obviously. CGR of a component crop is influenced by the CG R of the associated crop.
The negative LGRs of sorghum and pigeonpea at seed (pod) filling showed that there was delay in leaf senescence in the intercrops. It was a partial compen sation for decreased leaf dry matter under intercropping.
Panicle, or pod growth rates (pGR) were lower under intercropping during the initial stage of seed or pod filling in all the crops (Table 11). In the early component crops, the PGR continued to be less during later stage also. In the long duration crops, the adverse effect of intercropping on the PGR did not persist at later stage.
In fact, in pigeonpea intercropped with sorghum, the PGR was higher than that of sole crop, indicating that there was compensatory increase in pod growth at later stage.
Intercropping reduced net assimilation rates (NAR) of early component crops (Table II), indicating that they were less efficient in dry matter production per unit leaf area during reproductive phase due to the presence of the late component crops. Probably because of harvest of immature pods, the NAR of cluster bean was relatively less affected by intercropping than in sorghum and black gram. Long duration intercrops maintained more or less similar NAR as that of sole crops. The results of the present study show that decrease in the assimilation efficiency of leaves also contribute to lower rate of seed or pod growth in early component crops.
REFERENCES
Bala Subramanian. V. and Rao, D.G. (1988). Intercropping effects on yield components of dryland sorghum, pigeonpea and mung bean. Trop. Agrie. (Trinidad), 65: 145-149. Galwey, N.W., De Queiroz, M.A. and Willey, R.W. (1986). Genotypic variation in the response
GROWTH ANALYSIS OF iNTERtilOPS
if
Natarajan, M. and WilIey R.W.(I980). Sorghum-pigeonpea intercropping and the effects of plant population density. 2. Resource use. J. agic. Sci. (Camb.) 9S ; 59-65.
Ntare, B.K. (1989). Evaluation of cowpea cultivars for intercropping with pearl millet in the Sahelian Zone of West Africa. Field Crops Res., 20 : 31-43.
Ofori, F. and Stern, W.R. (1987). Cereal-legume intercropping system. Adv. Agron., 41 : 41-90. Shackel, K.A. and Hall, A.E. (1984). Effect of intercropping on the water relations of sorghum
and cowpea. Field Crops Res., 8 : 381-387.
