(Solanum tuberosum) and common bean (Phaseolus vulgaris)

1 downloads 0 Views 418KB Size Report
bean (Phaseolus vulgaris). The relations between potato tuber yield/plant and common bean density at various densities of potato and also with potato.
New & Zealand Journal of Crop and Horticultural Science,for2009, Vol. 37: 141–147 Raey Ghassemi-Golezani—Yield-density relationship potato and common bean 0014–0671/09/3702–0141 © The Royal Society of New Zealand 2009

141

Yield-density relationship for potato (Solanum tuberosum) and common bean (Phaseolus vulgaris) in intercropping

Yaegoob Raey Kazem Ghassemi-Golezani Department of Agronomy and Plant Breeding Faculty of Agriculture University of Tabriz Tabriz, Iran email: [email protected] Abstract  Methodologies of competitive interaction quantification between crops are not widely investigated. Therefore, field experiments (using addition series) were conducted in 2005 and 2006, to quantify interspecific and intraspecific competition coefficients and, also, the relative competitive ability (RC) of potato (Solanum tuberosum) and common bean (Phaseolus vulgaris). The relations between potato tuber yield/plant and common bean density at various densities of potato and also with potato density at different densities of common bean are well described by the reciprocal equations. Potato tuber yield/unit area decreased as common bean density increased. Optimum potato densities on the basis of maximum potato tuber yield/unit area at 0, 20, 30, and 40 plants/m2 of common bean were obtained at 14, 13, 12, and 12 plants/m2, as estimated by the parabolic relations between potato tuber yield/ unit area and potato densities at different common bean densities. Potato was a stronger competitor than common bean, as a potato plant was equal to 6.22 common bean plants, based on potato tuber yield. A common bean plant, also, was equivalent to 0.0475 of a potato plant, on the basis of common bean grain yield. Therefore, potato was more aggressive than common bean, indicating that potato tuber yield was mostly affected by intraspecific competition, whereas common bean grain yield was mostly affected by interspecific competition. Niche differentiation index (NDI) was smaller than 1, showing severe competition of two species for environmental H08057; Online publication date 4 June 2009 Received 15 May 2008; accepted 9 March 2009

resources. It was concluded that yield-density relations in intercropping could be well quantified by application of the proposed equations. Keywords  common bean; competition; inter­ cropping; potato; reciprocal equations INTRODUCTION Competition is defined as the mutually adverse effects of organisms (plants) that use a resource in short supply (Park & Watkinson 2002). Two types of competition occur: intraspecific and interspecific. Intraspecific competition is the negative interaction between plants of the same species and interspecific competition is the negative interaction between plants of different species. Measurement of the effects of plant interactions has been done through: (1) additive studies, which allow quantification of the effect on plants of one species by increasing the density of plants of a second species (Bleasedale 1967; Cousins 1991); (2) replacement studies, which allow determination of the effect of species proportion on plants of each species while keeping total plant density constant; (3) plant spacing studies, which allow determination of the effect of plant arrangement (Fisher & Miles 1973); and (4) studies combining density and proportion (Watkinson 1981). Roush et al. (1989) compared three approaches to describe competitive interactions between wheat and Italian ryegrass. These comprised conventional analysis of replacement series experiments, development of synthetic no-interaction responses from monoculture experiments for comparison with results from mixedculture, and responses of the reciprocal yield of individual plants to variation in densities of the two species. The three approaches varied in ability to quantify this competitive relationship. However, the reciprocal yield approach provided the simplest and the most sensitive analysis of the joint influences of density and proportion of species. Rejmanek et al. (1989) reviewed standard designs for two

142

New Zealand Journal of Crop and Horticultural Science, 2009, Vol. 37

species competitive experiments and demonstrated the advantages of a reciprocal yield model applied to the data from an additive series experiment. Park & Watkinson (2002) indicated that the reciprocal model accounted for 94% and 90% of the variation in the mean dry weight of maize and bean, respectively, grown in intercropping stands. In a plant community, after a saturation threshold plant density is reached, adding more plants will not increase yield on a per unit area basis. On an individual plant basis, as density increases, individual plant weight decreases non-linearly. When the inverse of individual plant weight is used as the dependent variable, the relationship of plant density to plant weight becomes linear and the regression coefficients that define the slope of the line quantitatively describe the importance of intraspecific and interspecific competition density effects on individual plant weight of the species in question (Roush & Radosevich 1985). These coefficients can be used to calculate the relative competitive abilities of each species being studied (Roush & Radosevich 1985; Oliver & Buchanan 1986; Roush et al. 1989). Raey et al. (2005) improved these equations to quantify the relationship of soybean grain yield with different densities of soybean and shatter cane. A similar approach could be applied to investigate other important intercropping such as common bean (Phaseolus vulgaris) with potato (Solanum tuberosum), to improve the validity of these models. Improving production of potato and common bean is a priority for many countries, to overcome the human population’s increasing need for food. Potato tubers and common bean grains may be considered as perfect food, because of their high starch and protein content, respectively. So, intercropping could be applied to make simultaneous production of these two major plants (non-legume and legume) possible. Thus, the objectives of this research were to: (1) test the equations introduced by Raey et al. (2005) to describe the relationship between potato tuber yield and common bean density; (2) estimate optimum densities of potato at different densities of common bean; and (3) evaluate the effect of common bean density on potato tuber yield, when grown simultaneously in competition with potato.

MATERIALS and METHODS Field expriments were conducted in 2006 and 2007 at the Research Farm of Ardabil University (38°15′N, 48°15′E, pH = 7, and elevation of 1350 m) in a

sandy loam soil. A potato cultivar (‘Agria’), and a common bean cultivar (‘Ziba’) were obtained from the Agricultural Research Centers of Ardabil and Karaj, respectively. The cultural pattern was an additive series. Treatments were potato densities of 10, 15, and 20 plants/m2, and common bean densities of 20, 30, and 40 plants/m2. In both years, a factorial set of treatments was arranged within a randomised complete block design with three replications. The desired plant population was obtained by overseeding and hand thinning. Weeds were controlled by hand weeding. Each plot size was 28.8 m2 and consisted of six rows, 6 m long and 80 cm wide. Yield data were collected from 12.8 m2 of the midle part of each plot. Rows were numbered 1–6 from left to right. Outside rows (rows 1 and 6) were border rows. Potato tubers were cut into small parts and subsequently these tuber parts together with commom bean grains were dried in an oven at 80°C for 72 h. Statistical analysis Since yield-density relations of potato–common bean intercropping for 2 years were statistically similar, means of 2 years of data for potato tuber and common bean grain yields were analysed via multiple linear regressions to select the appropriate model, using the density as an independent variable and potato tuber and common bean grain yield as dependent variables. Reciprocal equations (Raey et al. 2005) were used to describe the intraspecific and interspecific competition relationships for potato and common bean on a per plant basis: Potato: 1/Wp = Bp + Bp,p Np + Bp,b Nb

(1)

Common bean: 1/Wb = Bb + Bb,b N b + Bb,p Np

(2)

Aggressivity of potato = Bp,p/Bp,b

(3)

where 1/W p and 1/W b are the reciprocal yield/ plant of potato and common bean; Bp and Bb are the maximum yield of potato and common bean without competition; Bp,p and Bb,b are the regression coefficients for intraspecific competition or the effect of potato on potato and common bean on common bean; Bp,b and Bb,p are the regression coefficients for interspecific competition or the effect of bean on potato and potato on common bean; and Np and Nb are the density of plants of potato and common bean, respectively. The coefficients of intraspecific (Bp,p and Bb,b) and interspecific (Bp,b and Bb,p) competition were used to calculate the relative competitive ability (RC) also known as aggressivity (Equations 3 and 4), according to Rejmanek et al. (1989):

Raey & Ghassemi-Golezani—Yield-density relationship for potato and common bean Aggressivity of common bean = Bb,b/Bb,p

(4)

NDI = (Bp,p/Bp,b) (Bb,b/Bb,p)

(5)

143

When two species were competing for the same resources, the niche differential index (NDI) was calculated (Dunan & Zimdahl 1991):

RESULTS Influence of common bean   density on potato tuber yield The reciprocal of potato tuber yield/plant at all densities linearly increased as common bean density increased (Fig. 1). The values calculated for the intercept and slope of each regression line (Table 1) was used to estimate potato tuber yield/unit area (g/ m2) at various densities of common bean according to the equations presented in Table 2. The results showed that potato tuber yield/unit area decreased with increasing common bean density (Fig. 2). Potato tuber yield at low densities of common bean was more than that of high densities. The highest yield loss compared to the sole potato was observed in the treatment combination of 20 plants/m2 of potato and 40 plants/m2 of common bean (Fig. 2). The improved yield/density equations (Raey et al. 2005) were applied to describe relations between potato density and potato tuber yield/unit area at various densities of common bean (Tables 3 and 4). The relationship between reciprocal of potato tuber yield/plant and potato density was asymptotic

Fig. 1  Relations between the reciprocal of potato (Solanum tuberosum) tuber yield per plant and common bean (Phaseolus vulgaris) density at potato densities of 10 (dashed line, 1/w = 0.002799 + 0.0000505 × db), 15 (dotted line, 1/w = 0.0034 +0.0000818 × db), and 20 (solid line, 1/w = 0.006346 + 0.0000188 × db) plants/m2.

(Fig. 3), but the relation between potato tuber yield/ unit area and potato density at different densities of common bean was parabolic (Fig. 4). Potato tuber yield (g/m2) at 0, 20, 30, and 40 plants/m2 of common bean increased with increasing potato density up to 14, 13, 12 and 12 plants/m2, respectively. Further increases in potato density resulted in decreasing

Table 1  Equations for the reciprocal of potato (Solanum tuberosum) tuber yield per plant (1/w), at different densities of common bean (Phaseolus vulgaris) (db). Potato density (plants/m2)

Reciprocal equations

P value

R2

10 15 20

1/w = 0.002799 + 0.0000505 × db 1/w = 0.0034 + 0.0000818 × db 1/w = 0.006346 + 0.000188 × db

0.0001 0.0000 0.0001

0.88 0.94 0.87

Table 2  Equations for potato (Solanum tuberosum) tuber yield per unit area (Y) at different densities of common bean (Phaseolus vulgaris) (db). Potato density (plants/m2)

Yield/density equations

P value

R2

10 15 20

Y = 10/(0.002799 + 0.0000505 × db) Y = 15/(0.0034 + 0.0000818 × db) Y = 20/(0.006346 + 0.000188 × db)

0.0001 0.0000 0.0001

0.88 0.94 0.87

144

New Zealand Journal of Crop and Horticultural Science, 2009, Vol. 37

Fig. 2  Relations between potato (Solanum tuberosum) tuber yield per unit area and common bean (Phaseolus vulgaris) density at potato densities of 10 (dashed line, 10/(0.002799 + 0.0000505 × db)), 15 (dotted line, 15/(0.0034 + 0.0000818 × db)), and 20 (solid line, 20/(0.006346 + 0.000188 × db)) plants/m2.

Fig. 3  Relations between the reciprocal of potato (Solanum tuberosum) tuber yield per plant and potato density at common bean (Phaseolus vulgaris) densities of 0 (dashed line/closed triangles, 1/w = 0.006022 – 0.00095 × dp + 0.000355 × dp2), 20 (solid line/open squares, 1/w = 0.00784 – 0.00092 × dp + 0.0000488 × dp2), 30 (dashed line/closed squares,1/w = 0.010999 – 0.00141 × dp + 0.00034 × dp2), and 40 (solid line/open triangles, 1/w = 0.014804 – 0.00193 × dp + 0.0000966 × dp2) plants/m2.

Table 3  Equations for the reciprocal of potato (Solanum tuberosum) tuber yield per plant (1/w) at various potato densities (d p). Common bean density (plants/m2)

Reciprocal equations

P value

R2

0 20 30 40

1/w = 0.006022 – 0.00095 × dp + 0.000355 × dp2 1/w = 0.00784 – 0.00092 × dp + 0.0000488 × dp2 1/w = 0.010999 – 0.00141 × dp + 0.00034 × dp2 1/w = 0.014804 – 0.00193 × dp + 0.0000966 × dp2

0.0000 0.0000 0.0001 0.0001

0.96 0.94 0.86 0.9

Table 4  Equations for potato (Solanum tuberosum) tuber yield per unit area (Y) at various potato densities (dp). Common bean density (plants/m2)

Yield/density equations

P value

R2

0 20 30 40

Y = dp / (0.006022 – 0.00095 × dp + 0.000355 × dp2) Y = dp / (0.00784 – 0.00092 × dp + 0.0000488 × dp2) Y = dp / (0.010999 – 0.00141 × dp + 0.00034 × dp2) Y = dp / (0.014804 – 0.00193 × dp + 0.0000966 × dp2)

0.0000 0.0000 0.0001 0.0001

0.96 0.94 0.86 0.9

potato tuber yield at different common bean densities (Fig. 4). The highest potato tuber yield at all densities of potato was obtained under common bean-free treatments, and that was decreased with increasing common bean density (Fig. 4).

Quantitative analysis   of the species competitiveness The relations of the reciprocal of dry biomass tuber yield/plant of potato and per plant of common bean with their own density and with the density

Raey & Ghassemi-Golezani—Yield-density relationship for potato and common bean of the competitor species were calculated, using multiple linear regression analysis (Table 5). These relations are clearly shown in Fig. 5 and 6. The three-dimensional surface of each figure represents the expected values from the experimental data. Increasing the density of its plants (Np) per unit area led to an increase in the reciprocal of the dry biomass tuber yielded by potato (1/wp) ( Fig. 5). The coefficient of the potato density (Bp,p = 0.000666) quantifies the competition among potato plants (intraspecific competition) and the coefficient of the common bean density (Bp,b = 0.000107) quantifies the effect of this crop on potato plants (interspecific competition). The relative competitive ability (RC) of the potato versus common bean is defined by the ratio of the regression coefficients of Bp,p/Bp,b, on the basis of tuber dry biomass. The effect of adding one potato plant was equal to the effect of adding 6.22 common bean plants (0.000666/0.000107 = 6.22), as calculated by Equation 3. In other words, the addition of one potato plant has increased 1/wp, i.e., reduced the potato yield per plant (wp) to the same extent as the addition of 6.22 common bean plants. Increasing the density of its plants and potato cause an increase in the reciprocal of the grain dry biomass yielded by common bean (Fig. 6). The coefficients of the common bean density (Bb,b = 0.000261) and potato density (B b,p= 0.005545)

145

Fig. 4  Relations between potato (Solanum tuberosum) tuber yield per unit area and potato density at common bean (Phaseolus vulgaris) densities of 0 (dotted/dashed line, = d p / (0.006022 – 0.00095 × dp + 0.000355 × dp2)), 20 (dashed line, = d p / (0.00784 – 0.00092 × dp + 0.0000488 × dp2)), 30 (grey line, = d p /(0.010999 – 0.00141 × dp + 0.00034 × dp2)), and 40 (solid line, = d p / (0.014804 – 0.00193 × dp + 0.0000966 × dp2)) plants/m2.

quantify the competition among common bean plants (intraspecific competition) and the effect of potato on common bean (interspecific competition), respectively. One common bean plant has experien­ ced the presence of another common bean plant

Table 5  Summary of the multiple linear regression analysis of the reciprocal of tuber yield per plant of potato (Solanum tuberosum) and common bean (Phaseolus vulgaris) grain yield as a function of the density of the two species. Source of variation

d.f. MS

Potato Regression Residual

2 33



Coefficient

 Intercept –0.00565 Variable N p 0.000666 (Bp,p) Variable N b 0.000107 (Bp,b) Common bean Regression 2 Residual 33   Intercept Variable N b Variable Np

P value

0.00178 8.41 E-10 4.23E-06

R2 0.72

SE

t stat

P value

0.001406 8.39E-05

–4.02045 7.9259

0.000317 3.86E-09

2.32E-05

4.612374

5.75E-05

0.030353 2 E-12 0.000456

0.81

Coefficient

SE

t stat

P value

0.110277 0.000261 (Bb,b ) 0.005545 (Bb,p)

0.014592 0.000436

7.554009 0.597825

1.09E-8 0.554037

0.000481

11.524

4.14E-13

146

New Zealand Journal of Crop and Horticultural Science, 2009, Vol. 37

Fig. 5  Combined effects of potato (Solanum tuberosum) and common bean (Phaseolus vulgaris) densities on the reciprocal of tuber dry biomass per potato plant (1/wp).

Fig. 6  Combined effects of potato (Solanum tuberosum) and common bean (Phaseolus vulgaris) densities on the reciprocal of grain dry biomass/common bean plant (1/wb).

as strongly as the presence of 0.0470 potato plant. However, the probability of the intraspecific competition (Bb,b) being about zero was 55% (Table 5), meaning that there is 55% chance that common bean would not have interfered on its grain yield. The relative competitive ability of common bean in relation to potato (0.0470) shows that one common bean plant is approximately equivalent to 0.047 of a potato plant on the basis of common bean grain yield. Ecological niche differentiation was 0.223, as calculated by application of Equation 5.

2), because of increasing intraspecific competition among potato plants. Interferences between soybean and shatter cane (Raey et al. 2005) and wild oat and spring barley (Evans et al. 1991) also produced similar results. Optimum potato densities on the basis of maxi­ mum potato tuber yield/unit area at 0, 20, 30, and 40 plants/m² of common bean were obtained in the pure potato at 14, 13, 12, and 12 plants/m². Since yield-density relations of potato at different densities of common bean were parabolic, so further increase in potato density led to the reduction in tuber yield at all common bean densities (Fig. 4). The highest potato tuber yield at optimum plant populations was obtained in the potato pure stand and decreased with increasing common bean plant densities (Fig. 4). High relative competitive ability of potato (6.22), in comparison with that of common bean (0.047) suggests that the greatest effect of two species on each other is attributed to potato density. Lower interspecific competition in comparison to intraspecific competition on the basis of the reciprocal of potato tuber yield per plant (Table 5), indicates that the effect of a common bean plant is lower than that of a potato plant, as a common bean plant is equal to 0.16 of a potato plant (bp,b/ bp,p). In contrast, on the basis of common bean grain yield, interspecific competition is higher than intraspecific competition, as a potato plant is equal to 21.2 common bean plants (bb,p/bb,b). Therefore,

DISCUSSION The relationship between potato tuber yield/plant and common bean density at various densities of potato, and the relationship between potato tuber yield/plant and potato density at different densities of common bean are well described by reciprocal equations (Tables 1, 3; Fig. 1, 3). Subsequent application of the equations presented in Tables 2 and 4 to predict changes in potato tuber yield/unit area at different densities of common bean and potato was successful (Fig. 2, 4). Similar results are reported by Raey et al. (2005), describing interference between soybean and shatter cane. Increasing common bean density decreased potato tuber yield per unit area at various densities of potato. The highest tuber yield loss was observed at the highest tested density of potato (Fig.

Raey & Ghassemi-Golezani—Yield-density relationship for potato and common bean the superior competitor is mostly affected by intraspecific competition, and the weaker competitor is mostly affected by interspecific competition. Raey et al. (2005) reported that one shatter cane plant was equal to 2.5 soybean plants as measured by the effects of soybean and shatter cane densities on soybean seed yield. Reciprocal equations were also applied to quantify the aggressivity of common bean over Alexander grass (Passini et al. 2003), maize over bean (Park & Watkinson 2002), and Japanese millet over tomato (Rejmanek et al. 1989). Since NDI was smaller than one, there was no ecological niche differentiation. Therefore, two species strongly competed for environmental resources. It may be attributed to the same spatial arrangement and overlapping of root systems of potato and common bean and or to shade of the shoot systems of two species together and this needs to be investigated in future research. High intraspecific and interspecific competition of potato clearly suggests that potato plants have captured environmental resources more efficiently than common bean plants. Roush et al. (1989) also reported that NDI was smaller than 1 for wheat and ryegrass intercropping. In contrast, Raey et al. (2005) in soybean and shatter cane interference and Passini et al. (2003) in Alexander grass and common bean competition reported that NDI was greater than 1. Jolliffe & Wanjau (1999) reported that when the between-species competition in mixtures was low, as indicated by a NDI higher than 1, high productivity of mixtures in relation to monocultures occurred in accordance with ecological concepts of NDI. In the current research NDI was lower than 1, and the two species severely competed. Therefore, the productivity of intercropping in comparison with monocultures was low. CONCLUSION Yield-density relationship for potato and common bean was well described by the models introduced by Raey et al. (2005). These models can be used to quantify interspecific and intraspecific competition of potato and common bean, and enable us to predict optimum plant densities for potato at different densities of common bean. Therefore, intercropping of potato and common bean is beneficial in improving crop yield and economy per unit area, providing that the predicted optimum population densities are applied. Similar research on other crops can be used to verify these models in other lications over various years.

147

REFERENCES Bleasedale JKA 1967. The relationship between the weight of a plant part and total weight as affected by plant density. Journal of Horticultural Science 42: 51–58. Cousens R 1991. Aspects of the design and interpretation of competition (interference) experiments. Weed Technology 12: 664–673. Evans RM, Donald CT, Laurence T, Bahman S, Lish JM 2001. Wild oat (Avena fatua) and spring barely (Hordeum vulgare) density affect spring barely grain yield. Weed Science 5: 33–39. Fischer RA, Miles RE 1973. The role of spatial pattern in the competition between crop plants and weeds. Mathematics of Bioscience 18: 335–350. Jolliffe PA, Wanjau FM 1999. Competition and productivity in crop mixtures: some properties of productive intercrops. The Journal of Agricultural Science 132: 425–435. Oliver LR, Buchanan GA 1996. Weed competition and economic thresholds. In: Camper ND ed. Research methods in weed science. Southern Weed Science Society of America. Pp. 72–97. Park SE, Watkinson AR 2002. Estimating the optimal relative density combination of two crops in an intercrop. Journal of Applied Ecology 39: 416–426. Passini T, Christopfloleti PJ, Yada IFU 2003. Competivity of the common bean plant relative to the weed Alexander grass (Brachiaria plantaginea (Link) Hitch). Scientia Agricola 60(2): 259–268. Raey Y, Ghassemi-Golezani K, Javanshir A, Alyari H, Mohammadi A 2005. Interference between shatter cane (Sorghum bicolor L.) and soybean (Glycine max L.). New Zealand Journal of Crop and Horticultural Science 33: 53–58. Rejmanek M, Robinson G, Rejmankova E 1989. Weedcrop competition: Experimental designs and models for data analysis. Weed Science 37: 276–284. Roush LM, Radosevich SR 1985. Relationship between growth and competitiveness of four annual weeds. Journal of Applied Ecology 22: 895–905. Roush LM, Radosevich SR, Wagner RG, Maxwell B, Peterson TD 1989. A comparison of methods for measuring effects of density and proportion in plant competition experiments. Weed Science 37: 268–275. Spiters CJT 1983. An alternative approach to the analysis of mixed cropping experiments. I. Estimation of competition effects. Netherlands Journal of Agricultural Science 31: 1–11. Watkinson AR 1981. Interference in pure and mixed populations of Agrosiemma githago. Journal of Applied Ecology 18: 967–976.