Agroforest Syst (2009) 76:579–590 DOI 10.1007/s10457-009-9223-0

Productivity and nutrient uptake of newly released wheat varieties at different sowing times under poplar plantation in north-western India R. I. S. Gill Æ Baljit Singh Æ Navneet Kaur

Received: 17 March 2008 / Accepted: 11 March 2009 / Published online: 24 March 2009 Ó Springer Science+Business Media B.V. 2009

Abstract Standardisation of cultural practises is one of the primary objectives to make the system ecologically sustainable and economically viable. In this context, the present study was conducted to optimise the time of sowing in relation to newly released wheat varieties under 4–6 year old poplar block plantation. Six widely grown wheat varieties (PBW 502, PBW 343, WH 542, PDW 274, PBW 509 and PBW 373) were intercultivated during three consecutive crop growth seasons at three times of sowing (mid November, late November and mid December) under block plantation of poplar (Populus deltoides Bartr.) clone G-48. The grain yield and nutrient uptake of wheat varieties was higher in open conditions than under the trees. The wheat variety PBW 502 out yielded the rest of wheat varieties over different sowing times. The highest grain yield was recorded when crop was sown during mid November over the 3 years. Thus adoption of PBW 502 under poplar plantation would substantially improve the overall productivity of the system without any additional input cost. All the varieties performed better when sown early compared to one-month delay. The various growth parameters like tiller height and number, spike length and 100 grain weight contributed significantly towards higher grain yield in R. I. S. Gill (&)
B. Singh
N. Kaur Department of Forestry & Natural Resources, Punjab Agricultural University, Ludhiana 141004, India e-mail: [email protected]

early sown conditions (mid November) under poplar irrespective of its age of plantation. The nutrient uptake (N, P and K) by wheat straw and grain was higher in early sown crop with longer growth span than the late sown crop. The higher quantity of N, P and K was removed from soil by PBW 509, PBW 373 and PBW 343, respectively. Keywords Crop and tree parameters
Grain yield
Light intensity
Nutrient concentration

Introduction Rice-wheat (Oryza sativa L.–Triticum aestivum L.) cropping system is predominantly followed in the northwest India. This exhaustive cropping system, in this fertile plain of country, has deteriorated the status of soil and water. Such intensive cropping system has led to indiscriminate use of chemicals that have further worsened the nutrient balance, besides increasing the pest incidence, cost of production and environmental problems. There is a need for diversification from this over-exploiting cropping system. One of the viable options is the adoption of agroforestry. Trees have always remained an integral part of farming systems and the society of this region. Traditionally, farmers used to retain naturally growing trees like Dalbergia sissoo, Acacia nilotica, Azadirachta indica and Prosopis juliflora in their

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agricultural fields. Most of these trees are slow growing and incompatible with agriculture crops owing to their spreading crown. Thus with commercialization of agriculture, farmers shifted to fast growing tree species. Amongst the fast growing tree species, poplar is a preferred tree in agroforestry. This is due to its straight bole, small crown and winter deciduous nature that allows winter cropping with only marginal negative effect on crop yields. In poplar, leaf fall starts in October and by the month end about 13% leaves fall which gradually increase to 27 and 84% by the end of November and December, respectively. The trees become totally leaf less in January and February. New flush of leaves starts appearing by end March and the trees are fully flush by end April. Populus deltoides is the most widely planted species of poplar in India. It was introduced in India in the late 1950s and it has been estimated that 60,000 hectare equivalent plantations of poplar exist in India. It can be successfully planted on farm boundaries as well as in block plantations. Poplar based agroforestry system is a big success in irrigated regions of north-western India. In this region, high productivity of poplar up to 50 m3 ha-1 year-1 has been achieved through intensive management practises compared to 1.0 m3 ha-1 year-1 of natural forests (Lal 2007). The adoption of poplar based agroforestry system is driven by economic incentives and by the national policy to save natural forests from further deforestation. Trees modify the microclimate by reducing photosynthetically active radiation (PAR), air temperature, and by increasing the relative humidity (RH) in their understorey. The extent of this modification depends on the choice of agroforestry tree and the intercrop in a system. In the first 2 years of poplar plantation any crop can be grown without much reduction (10–15%) in the yield during summer and winter seasons. However during summer season, rice is not recommended for planting with poplar as flooding of rice often results in uprooting of trees (Dhanda et al. 2008). Third year onwards, during the winter season, different crops like wheat, oats (Avena sativa), berseem (Trifolium alexandrinum L.) etc. can be grown while during summer season, it is not economical to grow any crop. Wheat can be successfully grown under block plantation of poplar throughout its rotation. This is due to the ability of poplar to adapt to the wheat competition by distorting its root architecture that improves complementarity between trees and crops (Cannel et al. 1996).

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There is a gradual yield reduction (10–46%) of wheat, grown under poplar, with the increase in age of trees (first–sixth year). Such yield loss is often compensated by the sale of poplar wood at the end of rotation (Gill et al. 2007). Many workers have reported the performance of different wheat varieties as intercrop under poplar block plantation. In most of the studies, localised varieties were grown under poplar at the recommended date of sowing such as Inqalab-91 in Faisalabad (Chaudhry et al. 2003); PBW-226, WH542, HD-2329, PBW-154 and PBW-299 in Punjab (Pannu and Dhillon 1999); HS-295, Sonalika, HD2285 and HD-2380 in Himachal Pradesh (Chauhan and Dhiman 2007); HUW-234 in Bihar; HD-2285 in Uttar Pradesh (Sharma et al. 2001) and Sujata, Lok-1, Kanchan and GW-174 in Chhattisgarh (Puri et al. 2001). In most of these studies, the wheat varieties were evaluated based on their one year performance (Singh et al. 1993; Pannu and Dhillon 1999) or conclusions were drawn based on survey and discussions with farmers (Kumar et al. 2004; Jain and Singh 2000). Competition for below and above ground resources often changes with the increase in tree age. Thus, above results are not applicable for different aged poplar plantations. Therefore, the age of poplar plantation has been included in this study. The uptake of nutrients by crops is a function of yield and nutrient concentrations. The efficiency of crop nutrient uptake is determined by the environmental condition, the availability of nutrient in the soil and the crop growth stage (Kaya and Nair 2001). The crops vary in their nutrient uptake under various tree species as compared to open conditions. Lower removal of N, P and K by wheat grain and straw has been observed under different tree species namely Prosopis cineraria, Acacia leucophloea, D. sissoo and A. nilotica as compared to wheat in open condition (Yadav et al. 2005). Conversely, the crop in intercropped conditions i.e. the maize (Zea mays L.) in hedgerows of Gliricidia sepium lead to a significantly higher N uptake than the control (no hedgerows) (Zaharah et al. 1999). Therefore, the uptake of nutrients (N, P and K) by wheat varieties at different sowing times under open and intercultivated conditions was also evaluated. Wheat breeders have been constantly working to develop new varieties with improved productivity and resistance to emerging pests and diseases. Over a

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period new varieties replace the existing ones. During 2005, the Punjab Agricultural University had released PBW 502 as early and PBW 509 as late sown wheat variety for commercial cultivation in north-western India. These varieties were released based on their performance under open conditions. Maximum area is under wheat variety PBW 343 (63.35% of total area sown under wheat) and the area under PBW 502 is 21.09%. Under open conditions, the recommended time of sowing for these wheat varieties is from 4th week of October to 4th week of November. Differential response of wheat varieties was expected under shade. So popularly grown early and late wheat varieties were screened for 3 years under poplar. The main objective of the study was to find out partially shade tolerant/compatible wheat varieties that can be commercially grown under block plantation of poplar along with their optimum sowing time.

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variety with an average plant height of 90 cm. This long duration variety takes about 155 days to mature with an average yield of 4.62 Mg/ha. PDW 274 is an early sown variety of durum wheat with an average plant height of 90 cm. It takes about 153 days to mature with an average yield of 4.60 Mg/ha. The PBW 509 is a late sown variety with an average plant height of 85 cm. It takes about 130 days to mature with an average yield of 3.95 Mg/ha. The PBW 373 is another late sown variety with an average plant height of 90 cm. It takes about 140 days to mature with an average yield of 4.12 Mg/ha. Experimental design and statistical analysis

The study was conducted in poplar plantation established during 2000 at the Forestry Research Area of the Department of Forestry & NR, Punjab Agricultural University, Ludhiana. The site is located at 0 0 30°54 N, 78°48 E and 247 m above mean sea level. The region is characterised by a sub-tropical and semi-arid type of climate with hot and dry weather from April to June, hot and humid from July to September and cold from November to January.

Poplars were planted at a spacing of 5 9 4 m (widely adopted by farmers) with 5 m strip in the North South row direction. The area between the tree rows (5 m wide strip) was used to sow wheat varieties. Wheat varieties were sown on three dates [10–11 November (mid November), 25–26 November (late November) and 10–11 December (mid December)] during 2003– 2004, 2004–2005 and 2005–2006. The age of poplar plantation during these 3 years was 4, 5 and 6 years, respectively. The experiment was laid out in split plot design with four replications. The time of sowing was kept in the main block and wheat varieties in subplots. The crop data was analysed by analysis of variance technique (Panse and Sukhatme 1985). The F test and P values for different crop parameters and nutrient uptake were determined. The treatment means were separated by least significant difference (LSD) test at 5% level of significance.

Wheat varieties

Tree and crop management

Six wheat varieties viz., PBW 502, PBW 343, WH 542, PDW 274, PBW 509 and PBW 373 representing early and late sown varieties of north-western India were selected to test their performance under poplar block plantation. As per the package of practises for crops, PBW 502 is an early sown double-dwarf variety with an average height of 95 cm. It matures in about 150 days with an average yield of 4.87 Mg/ha. The variety PBW 343 is another early sown doubledwarf variety with an average plant height of 100 cm. It is a long duration variety that matures in about 155 days with an average yield of 4.75 Mg/ha. Cultivar WH 542 is also an early sown double-dwarf

Poplar plants require regular pruning to produce maximum volume of high quality knot free timber. Thick side branches that compete with the main stem were pruned during the dormant season (when plant is leafless) in all the years. The cropped area was managed in the same way as commercial crops i.e. receiving recommended application of irrigation, fertilisers, fungicides and insecticides. The ‘control’ was an area where different wheat varieties were sown without poplar and it was established in close proximity to the block plantation of poplar. This area was managed in the same way as the cropped area under trees. Wheat varieties with a seed rate of 100 kg ha-1

Materials and methods Site and climate

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were sown using seed-cum-fertiliser drill in rows 22.5 cm apart. Two hundred fifty kg urea and 125 kg DAP were applied in two split doses (half dose of N and full dose of P at the time of sowing and remaining half dose of N after first irrigation). Total 4–5 irrigations were given to the poplar plantation every year during the wheat-growing season. Measurements and analysis of plant samples The height and diameter of all the trees in the experimental plot were measured each year in March with the help of Ravi’s Multimeter and diameter tape, respectively. The data on light was recorded from ten different points randomly in the plantation once a month, thrice a day with the help of lux metre having 80 cm long light sensor (Luxmet-300 EXD5). The light data from the control area (open) was also recorded for comparison. The various growth and yield attributes of wheat viz., tiller height, tiller number, ear length and 100-grain weight were recorded. All the plants within plots were harvested and the aboveground biomass was recorded. The samples were then threshed to find out grain and straw yield on Mg ha-1 basis. From biomass and grain yield, harvest index was calculated. Nutrient uptake (N, P and K) by wheat crop was determined in the 6th year of poplar growth. The representative samples of grain and straw were ground. For determination of N concentration, the samples were digested in concentrated sulphuric acid in the presence of digestion mixture. The N concentration was determined by the modified kjeldahl method (Jackson 1973). For determination of P and K concentration, grain and straw samples were digested in the mixture of nitric acid and perchloric acid in the ratio of 3:1. The P concentration in the digest was determined by vanadomolybdo phosphoric yellow colour method and K concentration by flame photometer (Jackson 1973). The uptake of these nutrients was estimated from concentration of nutrients and yield of crop.

Results and discussion Weather parameters The average annual rainfall of Ludhiana was 650 mm out of which major portion was received during July

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to September. During the wheat crop season (October–April), mean maximum (37°C) and minimum temperature (7.8°C) were recorded during April and January, respectively during 2003–2004. Mean minimum temperature varied considerably from 7.8°C in January 2004 to 4.4°C in December 2005. Maximum RH (87%) was recorded in January 2004 and minimum (37%) in April 2006. Proportionately higher rainfall (67.8 mm out of the total 109.4 mm) was received only during the month of January 2004 which could be the reason for rise in RH and decline in minimum temperature. However, the total rainfall received during wheat season was maximum (184.8 mm) and well distributed during 2004–2005. Whereas, the crop growing season of 2005–2006 was hot and dry than the other years with a meagre total rainfall of 55.2 mm (Fig. 1). Tree parameters and light intensity The average tree diameter and height increased from 14.9 to 19.2 cm and 14.9 to 19.5 m, respectively in the span of 3 years (Table 1). The crown diameter was 4.35 m in 4 year and 4.75 m in 6 year old plantation. The light intensity increased from November till March and decreased in the month of April with the appearance and growth of new leaves. The mean light intensity under poplar plantation decreased from 60.1 k lux in the 4th year to 46.6 k lux in the 6th year during the crop season (Table 1). The under storey light when averaged over the crop season was 61.7, 57.6 and 49.6% of the total light received in open conditions during 4th, 5th & 6th year, respectively. Crop parameters Tiller height Significant difference with respect to wheat tiller height in the different aged poplar, under different time of sowing and among the wheat varieties was observed, as indicated by the main treatment effects (Table 2). The height of wheat tillers was significantly more under open conditions than under poplar. Gradual decrease (84.9–67.3 cm) in tiller height with the delay in sowing from early November to mid December was observed. This reduction in the tiller height may be ascribed to the reason that in late sown

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583 RH (%)

40

Max Temp

Min Temp

100 90

35

80 70 25

60 50

20

R.H. (%)

Min Temp (C), Max Temp (C)

30

40

15

30 10 20 5

10

2003-04

2004-05

April

March

Feb

Jan

Dec

Nov

Oct

April

March

Feb

Jan

Dec

Nov

Oct

April

March

Feb

Jan

Dec

Nov

0 Oct

0

2005-06

Fig. 1 Weather parameters during wheat season for three successive years of study

crop vegetative phase of the crop is shortened which adversely affects the growth characteristics of the crop. Amongst the six wheat varieties under evaluation, maximum tiller height was observed in PBW 502 that was at par with PBW 343 and PBW 373 whereas significantly lower tiller height was observed in PBW 509. Tiller number Number of effective tillers produced by a crop is an important parameter that determines the crop yield. An appraisal of the data presented in the Table 2 indicated a declining trend in the number of tillers with increase in age of poplar plantation. Significantly higher number of tillers were observed (101.1) under 4 year old poplar trees compared to 6 year old (77.8) poplar trees. It clearly indicates that the treecrop competitive interactions increase with increase in age of the poplar trees which might be due to different level of competition for light and soil resources under different aged plantations. Mcmaster

et al. (1987) observed that shading (50% of ambient light) from booting to 1 week after anthesis caused greater tiller mortality resulting in fewer spikes per plant. Similar findings were observed by Kemp and Whingwiri (1980) who reported that shading (20% of full sunlight) before anthesis resulted in reduced tiller number. Apart from reduced light intensity (Table 1), production of more leaf litter with increase in age of trees also hampers the crop germination & subsequent growth parameters. Narwal (1996) reported that poplar at its earlier stage caused very less harmful effect on the alley crops but older trees reduced the plant stand due to more production of leaf litter. Sharma et al. (2000) also confirmed that amount of leaf litter increases with age of poplar, which inhibits the seed germination and subsequent growth. With respect to time of sowing, the wheat crop sown during mid November produced significantly more number of effective tillers per metre row length than mid December sown crop. Higher metabolic activity along with longer vegetative period in the early sown crop may be responsible for higher

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Table 1 Growth parameters and light intensity under poplar block plantation during different years at Ludhiana, Punjab, India Growth parameters and light intensity

Poplar plantation age 4 years 5 years 6 years

DBH (cm)

14.89

17.21

19.2

Height (m)

14.95

17.99

19.5

4.35

4.5

Crown diameter (m)

4.75

Light intensity (k lux) [Under poplar plantation] November December

35.2 41.4

32.5 37.2

28.1 32.4

January

44.3

41.6

36.8

February

58.7

52.6

45.9

March

109.5

97.1

90.2

April

71.4

56.7

46.2

Mean

60.1

53.5

46.6

November

51.2

45.2

47.5

December

59.9

62.2

55.4

January

73.2

67.3

71.6

Light intensity (k lux) [Under open conditions]

February

85.8

81.2

85.7

March

148.2

137.4

145.2

April

165.7

164.2

158.2

Mean

97.3

92.9

93.9

tiller number compared with that in late sown crop. Kohli et al. (1997) also reported that delay in sowing of wheat under poplar plantation coincides with leaf shedding of poplar, which hinders the germination and emergence of wheat crop that ultimately results in the lesser number of tillers. The wheat variety PBW 502 produced significantly higher number of tillers although it was at par with PBW 343. Whereas, the lowest number of tillers/m row length were observed in late sown and short duration wheat varieties i.e. PBW 373 and PBW 509. The variation in effective tillers and yield of wheat varieties due to heterogeneity in genetic constitution has also been reported by Rawat et al. (2000). Spike length The length of the spikes decreased with increase in age of the poplars and with the delay in sowing time, although the differences were statistically non-

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significant. These results support the fact that growth parameters of crop decreased consistently and progressively as the age of trees increased. This reduction may be due to lower production of photosynthates under low light conditions as the light intensity decreased (Table 1) with increase in age of poplar plantations. Significant differences in spike length were observed with respect to varieties under poplar plantation (Table 2). Maximum and minimum spike length was observed in PBW 502 and PBW 373, respectively. Whereas, the rest of the varieties were statistically at par with respect to the spike length. Hundred-grain weight The hundred grain weight declined with increase in age of poplars. It was significantly lower in wheat crop grown under 6 year old poplar than 4 and 5 year old poplar, the latter two being at par with each other. This might be due to lesser availability of moisture and nutrients under older plantation for growth and development of crop. The root system of the crop is usually confined to the soil horizons that are also available to the roots of the trees, but the trees can also exploit soil volume beyond the reach of the crop. That is why the effects of moisture and nutrient competition are generally more severe for the crop component and the intensity of competition increases with increase in density and age of the trees. Apart from nutrient and moisture, shade is also the major limiting factor that increases with age of trees. Willey and Holliday (1971) reported that shading (28 and 54% of full light) during the period of ear development resulted in an appreciable decrease in number of grains and grain weight per ear. Significantly higher grain weight was observed in wheat crop sown during first fortnight of November as compared to late November and early December (Table 2). It clearly indicates that early sown crop produced comparatively bolder and healthy grains than the late sown crop that resulted into higher grain weight and grain yield. Immature and shrivelled grains were produced in late sown crop that remained in the milk stage during the period of high temperature. On the other hand, the early sown crop gets an advantage as it comes in the earing stage when the temperature is favourable. The grain development and maturity keep balance with the steady rise in temperature as

Agroforest Syst (2009) 76:579–590 Table 2 Crop growth parameters under open and as affected by age of poplar plantation, time of sowing and varieties of wheat at Ludhiana, Punjab, India

Main treatments

585

Tiller height (cm)

Tiller no./m row length

Spike length (cm)

100grain wt (g)

Harvest index

Open

83.6

104.1

9.08

4.72

0.34

4

71.8

101.1

9.35

4.38

0.31

5

76.4

95.1

8.31

4.14

0.30

6

73.4

77.8

8.31

3.48

0.30

LSD (P = 0.05)

6.66

6.08

NS

0.23

0.015

Mid November

84.9

100.5

8.93

4.63

0.36

Late November

76.6

95.5

8.79

4.15

0.33

Mid December

67.3

87.6

8.56

3.76

0.27

LSD (P = 0.05)

5.00

3.23

NS

0.15

0.013

PBW 502

79.1

104.5

9.17

4.65

0.33

PBW 509

70.9

88.6

8.64

4.27

0.34

PDW 274 PBW 343

75.5 79.8

93.5 99.1

8.79 8.92

4.19 4.34

0.31 0.31

Age of poplar (years)

Time of sowing

Varieties

PBW 373

77.3

86.1

8.40

4.10

0.30

WH 542

75.2

95.4

8.63

3.52

0.34

LSD (P = 0.05)

2.21

3.40

0.34

0.16

0.012

indicated by the 100-grain weight (Nainwal and Singh 2000). The drop in temperature from October to December plays an important role in determining the overall growth of plants. Saini et al. (1988) also reported that temperature had complex relationship with spikelet formation, ripening and grain yield than other weather parameters. Among the six wheat varieties screened under poplar block plantation, maximum grain weight was observed in PBW 502 and it was statistically superior to all the other varieties and minimum grain weight was observed in WH 542. Grain yield The grain yield of all the wheat varieties was significantly higher in open conditions during different sowing dates than under the trees (Table 3). Trees grown in an agroforestry system compete with agricultural crops for resources and result in reduction in crop yield. The grain yield of varieties PBW 502 and PDW 274 was higher than other varieties at different sowing dates. In poplar boundary plantation, water use of the system increased up to a distance of

6 m from tree line, which caused moisture stress to the wheat crop (Sharma et al. 2001). In wheat, a long photoperiod induces formation of flowers, which would have developed into leaves under a short photoperiod. However, during March–April poplar leaves start sprouting and by this time wheat crop enters into maturity. Hence shading by poplar leaves decrease the light intensity and ultimately it becomes one of the limiting factors for the decline in grain yield of wheat grown under poplar. The grain yield decreased significantly as the sowing of wheat was delayed. The higher grain yield of early sown crop was jointly attributed by the higher number of tillers, grain number and grain weight than that of late sown crop. Likewise in earlier studies, significant positive correlation was observed between number of tillers per unit area, grain weight and grain yield (Joshi and Singh 1983; Das et al. 1995). The emergence of poplar leaves cast shade to late sown crop due to its delayed maturity and consequently it may hamper the translocation of photosynthates from source to sink (Pannu and Dhillon 1999). In addition, the incidence of bird damage was more in late sown variety as compared to

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Table 3 Grain yield (Mg ha-1) of wheat varieties under different aged poplar plantation and in open conditions as affected by sowing dates Varieties

Age (years)

Time of sowing Mid November

PBW 502

PBW 509

PDW 274

PBW 343

PBW 373

WH 542

Mean (varieties) Late November

Mid December

Open

4.45

2.89

2.15

4

3.48

2.52

2.09

5

2.89

2.47

1.73

6

2.78

2.07

1.35

Open

4.57

2.2

1.76

4

2.47

2.17

1.77

5

2.2

2.02

1.78

6

2.36

2.13

1.76

Open

3.79

2.76

2.08

4

2.96

2.2

1.97

5 6

2.76 2.59

2.03 1.96

1.85 1.38

Open

4.13

2.65

1.73

4

2.98

2.27

1.43

5

2.65

2

1.73

6

2.5

1.67

1.23

Open

4.15

2.29

1.83

4

3.16

2.1

1.66

5

2.79

2.02

1.68

6

2.58

2.02

1.03

Open

4.27

2.48

1.8

4

3.52

2.34

1.68

5

2.48

2.09

1.7

6

2.35

1.83

1.2

3.12

2.22

1.68

Mean (sowing time)

2.57

2.27

2.36

2.25

2.28

2.31

Mean (ages): open = 2.89, 4 years = 2.38, 5 years = 2.16, and 6 years = 1.93 LSD (P = 0.05) Age: 0.078 Sowing time: 0.070 Varieties: 0.099 Age 9 sowing time: 0.139 Age 9 varieties: 0.197 Sowing time 9 varieties: 0.171 Age 9 sowing time 9 varieties: 0.341

early sown crop. Randhawa et al. (1992) reported that in the late sown crop the flowering period is shortened because by the time it comes to flowering, the atmospheric temperature starts rising. During the non-foliated period, the impact of the canopy on direct and diffuse radiation is small (Douglas et al. 2006). Therefore the late sown crop is forced to flower and mature early.

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The grain yield of different wheat varieties differed significantly. The average grain yield was the highest in PBW 502 (2.57 Mg ha-1), which was significantly higher than all the other varieties (Table 3). Variation in wheat yield may be attributed to genetic variation in response to shade and stress of nutrient and moisture caused by the trees. Varieties having attributes like higher spike number, grain

0.00757 2.69 11.34 2.95E-11 0.01208 3.18 5.19 0.00042 4.82 0.01094 51.99 1.45E-14 Total uptake of K 162.11 6.8E-20

7.45445E-05

8.92E-06 5.3

5.19 1.16772E-05 4.45

11.15 4.14E-11 0.00204

0.00355 3.9

4.23 2.36E-05 7

5.13 0.00046 1.93 0.15279

3.55 0.0340 110.92 1.99E-22

61.32 4.09548E-16 94.06 1.40473E-14 Total uptake of P

Total uptake of N 168.78 2.51E-20

0.00106308

0.00039308 2.31 3.14 0.0010053 1.2483E-08 5.24 12.98 8.6462E-11 25.06 3.208E-09 108.86 9.1788E-13 9.4016E-05 25.8 Harvest Index

0.799167 0.77

2.16 3.0196E-05

1.82 0.059917

4.2 0.06966406

0.056216 1.69

1.63 40.74 6.6955E-28

4.91 0.000309 2.27 0.070754

9.42 2.353E-05 70.22 9.3421E-11

3.08 0.06447 0.100918 2.8

51.75 5.33E-06 100-grain wt

38.68 1.80702E-05

Spike length

3.86E-05

0.000995563 5.37 6.17911E-07 2.17 0.000103534 2.29 0.068709885 31.42 6.36427E-23 3.21

0.059422463

Tiller number

34.13 9.60226E-08

2.65 2.21 0.019088

2.06 0.029909795 1.49 0.00343192

6.09E-05 3.33

13.11 6.88322E-11 2.4

16.84 1.22E-13 1.74 0.154828

5.79 0.00076574

6.34 0.013391 Tiller height

26.83 7.59E-07

7.88 0.006908 Straw yield

39.21 2.74E-08

8.83E-05 2.53 3.96 6.71E-05 1.98E-12 7.29 11.63 9.51E-10 96.88 1.28E-15 1,101.19 2.46E-24

F test P value F test P value F test P value F test P value F test P value P value

F test

P value

A*ST*V ST*V A*V Variety

F test

178.59 2.46E-08

The concentration and uptake of N, P and K by wheat grain and straw during different sowing times were

Grain yield

Concentration and uptake of nutrients (N, P and K)

A*ST

Harvest index was significantly influenced by the different treatments. It was maximum under open conditions and decreased with increase in age of the plantation. It could be due to lesser vegetative growth viz. tiller height, number and straw weight under higher aged plantations resulting into higher value of harvest index (ratio of grain yield to total biomass). Similarly declining trend was observed in the harvest index with delayed sowing of wheat from mid November to mid December under poplar plantation. Maximum harvest index was obtained in November sown crop and minimum in December sown crop. Amongst the various varieties, maximum harvest index was recorded in PBW 509 and WH 542 followed by PBW 502, all these being statistically at par with each other. The PBW 509 being a short duration and late sown variety had lesser vegetative and reproductive growth compared to other varieties like total number of tillers and tiller height, straw and grain yield (Table 2), which contributes towards total biomass production and higher harvest index. Thus this variation in harvest index might be due to the variation in grain yield and total biomass production with increase in age of poplar. The P values indicated that grain yield was highly significant (P \ 0.001) as affected by age, sowing times and their interactions (Table 4). Straw yield was significant at P \ 0.05 for age and highly significant for sowing time and variety (P \ 0.001). The interactions except Age 9 Sowing times 9 Varieties were significant at P \ 0.05. Similarly, the significance of other parameters varied under different treatments and their interactions.

Sowing time

Harvest index

Age

number/spike and grain weight and with duration of minimum 1 month from anthesis to maturity are likely to perform better under late sown conditions. Significant inter-varietal and intra-environmental differences were observed in four wheat varieties tested under Ceiba pentandra (L.) Gaertn. plantation (Puri et al. 2001).

587

Table 4 Results of various wheat growth and yield parameters under different aged poplars, time of sowing and varieties using three-way analysis of variance

Agroforest Syst (2009) 76:579–590

123

588

Agroforest Syst (2009) 76:579–590

29.2%, respectively from the uptake of these nutrients under the 6 year old poplar plantation. This might be attributed to higher biomass yield in open conditions than under the trees. The total uptake of nutrients decreased significantly with delay in sowing time, when averaged over two environments and different varieties. The average uptake of N by grain reduced by 41.9%, P by 39.1% and K by 59.6% as the time of sowing was delayed from mid November to mid December (Table 5). The uptake of N and P by wheat straw was significantly higher during first date of sowing than other dates. The highest uptake of nutrients during mid November sowing date might be attributed to the highest grain and straw produced during this time. The uptake of K by wheat straw was considerably higher than the uptake by the grain which might be due to higher K concentration in wheat straw than its grains. Similar findings were reported by Dubey and Sharma (1996). Khalifa et al. (1977) observed that nitrogen uptake was higher during early sowing (1st November) of wheat, which resulted in better leaf expansion, higher leaf area

evaluated in open and under 6 year old poplar plantation (Table 5). Nutrient concentrations in wheat grain and straw differed in two environments, during different sowing times and amongst the various wheat varieties, as indicated by the main treatment effects. In grains, the concentration of N was highest followed by K and P, whereas the concentration of K was highest in straw followed by N and P in open as well as under poplar during different sowing times and in various wheat varieties. This variation in nutrient concentration of wheat varieties could be due to variable genetic potential of varieties to extract nutrients from the soil. Parihar and Tiwari (2003) observed that the concentrations of N and P in four wheat varieties (DL 788-2, DL 803-3, GW 190 and GW 173) were higher in grain than the straw whereas the concentration of K was higher in straw than their grains. The total uptake of nutrients as well as uptake by grain and straw was significantly higher in open environment as compared to the uptake under poplar plantation (Table 5). The total uptake of N, P and K in open conditions was higher by 33.5, 34.6 and

Table 5 Nutrient concentration and uptake through grain and straw of wheat varieties in open and under 6 year old poplar at different sowing times at Ludhiana, Punjab, India Main treatments

Uptake (kg ha-1)

Concentration (%) Grain N

Straw P

K

N

Grain P

K

N

Total uptake (kg ha-1) Straw

P

K

N

P

K

N

P

K

Environments Open

1.67 0.45 0.73 0.71 0.20 1.39 51.31 14.08 23.70 35.11 10.05 68.11 86.41

24.13

91.82

6 years

1.94 0.46 0.79 0.70 0.24 1.44 37.12

17.93

71.05

3.33

1.28

3.25

Mid November

1.70 0.42 0.89 0.74 0.24 1.30 56.91 14.63 30.45 35.43 11.32 61.98 92.33

25.95

92.43

Late November

1.78 0.43 0.67 0.67 0.21 1.47 42.64 10.59 16.25 29.14

8.77 63.27 71.78

19.36

79.53

Mid December

1.94 0.52 0.73 0.72 0.22 1.48 33.09

8.91 12.31 29.48

8.87 60.02 62.57

17.78

72.34

0.88

0.75 NS

4.08

1.56

3.98 77.35

LSD (P = 0.05) 0.05 NS Time of sowing

0.03 NS

0.02 NS

LSD (P = 0.05) 0.06 0.03 0.04 0.03 0.02 0.07

1.88

2.31

8.68 15.64 27.59

9.25 55.41 64.71

0.72

0.62 2.21

1.17

1.43

1.63

2.00

Varieties PBW 502

1.82 0.46 0.71 0.65 0.20 1.34 45.90 11.34 18.44 28.82

8.63 58.91 74.73

19.97

PBW 509

1.83 0.45 0.75 0.66 0.20 1.42 53.90 13.43 23.00 28.98

8.58 60.59 82.89

22.01

83.59

PDW 274

1.86 0.42 0.74 0.78 0.18 1.30 43.14 10.01 18.42 35.56

8.49 59.60 78.70

18.50

78.02

PBW 343

1.82 0.48 0.86 0.79 0.24 1.54 41.07 11.75 21.68 34.88 10.12 67.32 75.94

21.86

89.00

PBW 373

1.69 0.49 0.79 0.65 0.29 1.47 37.72 11.05 18.64 28.83 12.45 63.98 66.55

23.49

82.62

WH 542

1.80 0.45 0.73 0.74 0.23 1.43 43.55 10.68 17.84 31.02

20.35

78.02

2.21

5.63

LSD (P = 0.05) 0.08 0.04 0.05 0.05 0.03 0.10

123

3.26

1.25

2.02

2.83

9.67 60.18 74.56 1.07 3.82

5.77

Agroforest Syst (2009) 76:579–590

indices and higher leaf area duration. On the other hand, nitrogen uptake was much lower in late sowing (6th December) of wheat, which resulted in decreased leaf expanses, reduced leaf area indices and leaf area duration and thus lower grain production. Amongst the various wheat varieties, the total uptake of N was the highest (82.9 kg ha-1) by PBW 509 and the lowest (66.6 kg ha-1) by PBW 373. The total uptake of P and K was highest in PBW 373 and PBW 343, respectively. Likewise, the uptake of N, P and K by wheat grain and straw differed significantly amongst various wheat varieties. The higher uptake of nutrients by PBW 509, PBW 343 and PBW 373 might be due to relatively higher nutrient concentration and biomass of these varieties than the others. Parihar and Tiwari (2003) observed that nutrient concentration and content in grain as well in straw significantly varied amongst different wheat varieties and reported that the total uptake of the nutrients was higher in DL 788-2 cultivar followed by DL 803-3 due to significantly higher biomass of these varieties compared to GW 190 and GW 173. The P values for total uptake of N, P as well as K were highly significant (P \ 0.001) for age, sowing time and variety (Table 4). The interaction of Age 9 Sowing times for total uptake of N and K was significant at P \ 0.05 whereas for P, it was nonsignificant. The other interactions for the total uptake of nutrients were significant except K for Age 9 Varieties.

Conclusion The quantum of yield was recorded to be significantly higher in open conditions followed by four-year-old poplar plantation and it decreased with increasing age of plantation. This decrease was due to the increase in both above and belowground competition between trees and crop components in an agroforestry system. The maximum wheat yield was obtained when crop was sown during first fortnight of November in open as well as under the 4–6 year old poplar plantations compared to further delay in sowing. Best wheat variety under this optimum sowing time as well as under late sown conditions was PBW 502. Nutrient uptake (N, P and K) by wheat grain and straw was higher during the early sowing of wheat varieties in open conditions as well as under poplar and the

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uptake gradually decreased with the delay in sowing time. The highest uptake of N, P and K from soil was observed in PBW 509, PBW 373 and PBW 343, respectively. Acknowledgments The authors acknowledge the financial assistance from the Indian Council of Agricultural Research (ICAR) through the All India Coordinated Research Project on Agroforestry to the department. The authors are thankful to anonymous reviewers for their valuable suggestions that have substantially improved the quality of the manuscript.

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