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Agro-physiological traits and dry matter accumulation of corn grown under varying row and plant spacing

Abdul Khaliq1, Manzoor Ahmad2 and Riaz Ahmad3

Department of Agronomy, University of Agriculture, Faisalabad 38040 Pakistan www.uaf.edu.pk 1Email khaliquaf@gmail.com
2
Email manzoorune@yahoo.com
3
Email riazahmaduaf@hotmail.com

Abstract

Corn is an important cereal grown globally under varying agro-environments and contributes significantly to food security. Poor stand densities under farmer’s field are often responsible for yield gaps. Studies on patterns of leaf area development, growth and dry matter accumulation of corn grown under varying row and plant spacing were carried out for two years under semi-arid environments. Maximum LAI (6.87) recorded at 15 cm plant spacing was 11% and 26 % higher than that for 22.5 and 30 cm plant spacing. Highest TDM was recorded for planting at 45x15 cm spacing. Narrowing the row spacing from 75 to 60 cm at 15 cm plant spacing resulted in marked increase (39%) in TDM. Nonetheless TDM was quite low at 30 cm plant spacing but decreasing row spacing from 60 cm to 45 cm resulted in pronounced increase (27%) in TDM as compared with 15 cm plant spacing. TDM continuously increased when row spacing was reduced keeping plant spacing at 15 cm. Maximum grain yield (7606-7027 kg/ha) was recorded when corn was planted at 60x15 cm spacing as against the lowest (4454-4487 kg/ha) recorded for 75x30 cm spacing. Reducing plant spacing from 30 to 15 cm at 75 cm spaced rows enhanced grain yield by 29%. Trends in dry matter and yield shifts are discussed with either of the changing variable/s of row and/or plant spacing.

Key Words

Corn, leaf area development, grain yield, population density

Introduction

New corn hybrids with varying morpho-physiological traits are available in the market and management options may vary for such hybrids. Sangoi et al (2002) demonstrated that the optimum population of three hybrids released in Brazil during the 1970s, 1980s and 1990s was 7.1, 7.9 and 8.5 plants/m2, respectively. Owing to this tolerance of newer hybrids to high plant populations, its increase has been key to change in agronomic management over the past six decades (Tollenaar and Lee, 2002). Modern hybrids show a flexible response to increasing density and with an increase in plant density the individual plant size decreases but the yield per unit area improves. The number of plants/ha can only be increased to a limited extent, because above the optimal spacing the number of barren plants increases and thus the yield decreases. Newly developed hybrids have also exhibited decreased lodging at raised plant populations (Tollenaar, 1989), These hybrids are also tolerant to environmental stresses with fewer barren plants (Tollenaar, 1991). Higher plant population is required for such hybrids to develop leaf area indices that provide maximum light interception, and hence maximum grain yield. Genetic improvement of maize hybrids for higher yields demands their continuous evaluation as optimum plant population is likely changed whenever a newly developed hybrid is recommended for general cultivation in an area (Cox, 1996). Present studies were designed to quantify the agro-physiological and yield response of hybrid maize to varying row and plant spacing.

Methods

A modern early maturity corn hybrid, DK-919 was grown in 4 replicates with row spacing of 45, 60 and 75 cm in main plots and an inter plant distance of 15, 22.5 and 30 cm in sub plots at the Agronomic Research Area, University of Agriculture, Faisalabad, Pakistan for two successive seasons during autumn 2006 and 2007. The climate of the region was subtropical to semi-arid. The experimental area was located at 73o East longitude, 31o North latitude and at an altitude of 135 m above mean sea level. Soil was sandy loam in nature with a pH of 7.8, EC 0.5 dS/m, 0.905% organic matter, 0.055% total nitrogen, 935 ppm available phosphorus and 144 ppm available potassium. In each treatment/plot, six rows of 7 m length were sown during 1st week of August each year by dibbling 2 seeds per hill. NPK at 150, 100, 100 kg/ha, respectively was applied in the form of urea, diammonium phosphate and potassium sulphate . Application of N was equally distributed across sowing, 30 DAS and 60 DAS. To ensure moisture was non-limiting, crop was irrigated weekly till anthesis and fortnightly thereafter. Seven harvests including final harvest were made in both the experiments during both the years. On each harvest, three plants were selected from each plot leaving appropriate borders. The plants were cut at the ground level on all the harvest dates and separated into leaves, stem and fresh weights of each recorded separately. An appropriate sub sample of leaves was taken to estimate LAI using an area meter (Licor, Model 3100) at a regular interval of fifteen days from 30 to 105 DAS. Sub samples were oven dried to a constant dry weight at 70 C 3. Dry weights of sample plants were converted into m-2. Two central rows of 6 m length from each sub plot were harvested on physiological maturity; the cobs were air-dried and threshed manually. Grain weight was recorded (13% moisture content), and converted to kg ha-1. Data collected were analyzed by ANOVA and LSD test (P=0.05) was used to compare the difference/s among treatments’ means (Steel et al., 1997).

Results

During both the years the 45 cm row spacing exhibited greatest LAI cf. other row spacings (Fig. 1). Maximum LAI (6.87) recorded at 15 cm plant spacing was 11% and 26 % higher than crop sown at 22.5 and 30 cm plant spacing respectively (Fig. 1). Decreasing spacing increased LAI throughout crop growth.

Leaf area index

Days after sowing

Figure 1. Patterns of leaf area index with time. Comparison at different row and plant spacing a) 2006 b) 2007.

At final harvest, total dry matter (TDM) recorded under 45 cm row spacing was 17 and 34 % higher than that produced at 60 cm and 75 cm row spacing, respectively (Table 1). TDM of 60 cm spaced rows was 22% more than that for 75 cm spaced rows. Narrowing plant spacing from 30 to 22.5 cm resulted in 25% increase in TDM. While TDM was quite low at 30 cm plant spacing, decreasing row spacing from 60 cm to 45 cm resulted in more pronounced increase (27%) in TDM when compared with 15 cm plant spacing.

Maximum grain yield (6739 and 6245 kg/ha) was recorded in 45 cm spaced row spacing (Table 1). Grain yield of corn planted at 45 cm row spacing was 7% and 17% higher than that planted at 60 and 75 cm row spacing, respectively. Highest grain yield (6752 kg/ha) was realized from plots planted at 15 cm plant to plant distance. Corn planted at 15 cm plant spacing produced 24% more grains than that harvested from 30 cm plant spacing. During both the years of experimentation, the response to increasing plant density was linear in nature (Fig. 2). Maximum grain yield (7606 and 7027 kg/ha during 2006 & 2007) was recorded when corn was planted at 60x15 cm spacing (1, 11,111 plants ha-1). At row spacing of 75 cm, reducing the plant to plant distance from 30 cm to 15 cm resulted in 29% increase in grain yield that was 18 and 12% when corn was planted at 60 and 45 cm spaced rows respectively. Optimum row and plant spacing for maximum grain yield was 60x15 cm while for 45 cm row spacing 22.5 cm plant spacing appeared to be optimum. Lower harvest indices in present studies are attributed to increasing barrenness at higher densities. Kiniry et al. (2005) reported a decrease in harvest index at a rate of -0.012 units per plant/m2 above a threshold density of >10 plants/m2.

Table 1. Effect of row and plant spacing on total dry matter and grain yield of hybrid corn.

Treatments

Final total dry matter (kg/ha)

Grain yield (kg/ha)

2006

2007

Mean

2006

2007

Mean

Row spacing: (cm)

75

13390 c

12914 c

13152

5538 c

5274 a

5406 (0.41)

60

17566 b

16406 b

16986

6318.1 b

5787 b

6052 (0.36)

45

20828 a

18687 a

19758

6738.7 a

6245 c

6492 (0.33)

LSD (P ≤ 0.05)

1218

1248

 

332

386

 

Significance

**

**

 

**

**

 

Plant spacing: (cm)

30

12580 c

12018 c

12299

5276 c

4943 c

5109.6 (0.42)

22.5

17274 b

15583 b

16429

6323 b

5853 b

6088.4 (0.37)

15

21929 a

20406 a

21168

6995 a

6509 a

6751.8 (0.32)

LSD (P ≤ 0.05)

1152

938

 

292

355

 

Significance

**

**

 

**

**

 

Interaction:

R x P

*

*

 

**

**

 

Mean

17261

16002

16632

6198.1

5768.4

5983.3

Figures in the same column with different letters differ significantly at P ≤ 0.05 by LSD test. Figures in parenthesis show harvest index.

Grain yield (kg/ha)

Plant spacing (cm)

Fig. 2. Relationship between plant spacing and grain yield (kg/ha) at three ridge spacing during a) 2006 and b) 2007.

Discussion

Leaf area index in present studies increased with increasing plant density owing to reduced row/plant spacing. Crop canopy size and architecture are often associated with photosynthetic efficiency, and are affected by plant growth and changes in row or plant spacing’s (Girardin and Tollenaar, 1994). These influence leaf area index and grain yield (Tollennar and Bruulsema, 1988). At a constant plant density, an increase in leaf area index and in the efficiency of light interception per unit leaf area under narrow row spacing (Bullock et al 1988) means that a higher percentage of incident radiation would be intercepted than would be under wide rows (Bullock et al., 1988; Teasdale, 1995). Cox (1996) found that corn forage dry matter (DM) increased as plant density levels were increased. Our findings suggested a linear trend of DM with respect to increasing planting density while Cusicanqui and Lauer (1999) reported a quadratic yield response to plant density, with a maximum DM yield at plant density levels between 97300 and 102200 plants ha-1.

Grain yield advantages associated with higher planting densities observed in present studies are in agreement with many previous findings. Porter et al. (1997) reported that decreasing row spacing resulted in 4% more grain yield. Barbieri et al. (2000) and Karlen and Kasperbauer (2000) reported that narrow rows had yield advantages over conventional for corn. Several other authors (Sangoi et al., 2001; Widdicombe and Thelen, 2002; Johnson and Hoverstad, 2002)) have also reported that corn yields may be increased by reducing row spacing across the range of plant densities. Shapiro and Wortmann (2006) reported that corn grain yield typically exhibits a quadratic response to plant density with a non-linear increase across a range of low densities a gradually decreasing rate of yield increase relative to density increase and finally a yield plateau at some relatively high plant density.

Conclusion

Two years of field experiments demonstrated that corn hybrid DK-919 (an early maturing) should preferably be grown at inter and intra row spacing of 60 cm and 15 cm (111 111 plants/ha) for obtaining higher grain yields under irrigated conditions.

References

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