Allelopathy

Allelopathic potential of crop residues for weed management in wheat under semi-arid conditions of Pakistan Muhammad Ashraf Professor of Agronomy, PMAS-Arid Agriculture University, Rawalpindi, Pakistan. [email  protected] com RATIONALE †¢ Rainfed Wheat- Main winter crop grown by about 80% of the farmers on residual soil moisture, received during monsoon1. †¢ Weeds infestation- a major yield reducing factor (25-30%v); †¢ If weeds are controlled, crop yield can be enhanced by about 37%2. 1 Khaliq et al. , 2007) 2 (Bibi et al. , 2005). Cont†¦..Existing Weed Control systems: †¢ Traditional weed control methods (Hand weeding) are time consuming, weather dependent and labor intensive1 ; + Socio-economic issues:[small land holdings, family size =8, poverty, migration to cities] †¢ Herbicides use is limited in drylands + these are expensive with Environmental hazards2; Reduced Nutritive value of many crops 3 and Herbicide resistance4. 1 (Naveed et al. , 2008) 2 (Mancini et al. , 2008) 3 (Nazarko et al. , 2003). Cont†¦.. †¢ WM programs should focus on environmental safety along with benefits to the farmers. Alternate weed management systems need to be developed aimed to control weeds and raise the income of resource-poor farmers (increased crop yields) without despoiling the natural resource base. ALTERNATE WEED MANAGEMENT OPTIONS †¢ Allelopathy ? a mechanism of plant interference1 is a natural, inexpensive, environmentally safe and an organic approach to control weeds and increase crop yields while conserving the ecosystem2. †¢ Sorghum is highly allelopathic3 †¢ Sorghum residue may be effectively used to manage some of the important weeds in rainfed wheat without affecting crop in semi-arid environment4. (Weston, 2005) 2 (Inderjit and Duke, 2003) 1 (Weston and Duke, 2003) 2 (Inderjit and Duke, 2003) Cont†¦.. †¢ Water Extracts of different plant parts have different allelopathic potential 1. †¢ Sunf lower – possessed weed suppression ability 2 . †¢ The combination of two or more allelopathic aqueous extracts may act synergistically and cause more phyto-toxic effect on weeds 3. †¢ Mixing and applying sunflower and sorghum residue water extract (WE) may increase the spectrum of phytotoxic effects and may result in synergistic phytotoxic influences on weeds growth. 1 (Ben-Hammouda, et al. 001; Chung, et al. , 2003; Roth et al. , 2000) 2 (Bertholdsson, 2004; Singh et al. , 2001 ) 3 (Duke et al. , 2000; Cheema et al. , 2010) Cont†¦.. OBJECTIVES OF RESEARCH Overall objective: Evaluate the use of allelopathic crop residue collected from summer crop plants grown under drought and mineral stress conditions for weed management in wheat in semi-arid areas of Pakistan: Specific Objectives: †¢ Test water extracts (WE)of different plant parts of sorghum residue for weeds suppression in wheat. †¢ Evaluate the effects of sorghum residue mulch and sorghum WE for weed management in wheat. Investigate the influence of sole and combined sorghum and sunflower WE spray on weeds in wheat. EXPERIMENTAL DETAILS †¢ Location: Three experiments were conducted at University Research Farm, PMAS-Arid Agriculture University, Rawalpindi, Pakistan (33o 46 N, 73o 08 E). / / †¢ ~500 m above the sea level †¢ Experimental years: successive Rabi (winter) seasons from 2007-2010. Cont†¦.. †¢ Environmental Characterization: Climate Rainfall and ET o 200 160 Rainfall and ET0 (mm) 160 143 120 ETo 80 40 0 Oct Nov Dec Jan Feb Mar Apr Rain 140 121 Mean Monthly Rainfall (mm) 20 100 80 67 60 40 26 57 56 Sever Stress Period 27 21 7 15 39 43 20 0 Month Rainfall Distribution (1977-11) Source: Soil and water conservation Research Institute, Chakwal, Pakistan Growing Season Rainfall Period Monthly rain (mm) Oct Nov Dec Jan Feb March April Total 2006-07 2007-08 2008-09 2009-10 Long-term Av. (1977-07) 0 42 30 0 166 147 14 20 7 15 27 39 56 43 Soil charact eristics †¢ Rawal soil series (Inceptisol-silty-clay-loam, Typic Ustochrept USDA classification and Calcaric Cambisols FAO classification scheme) with †¢ Organic matter 0. 5%. †¢ pH 7. 40 †¢ Ece 3 dSm-1 Cont†¦.. Weed Flora †¢ Anagallis arvensis L. (Blue pimfernal), †¢ Chenopodium album L. (Lambs quarter), †¢ Fumaria indica L. (Fumitory), †¢ Medicago polymorpha L. (Bur clover) †¢ Avena fatua L. (Wild oat), †¢ Convolvulus arvensis L. (Field bindweed), †¢ Medicago denticulata L. (Denticulate Medick), †¢ Rumex dentatus L. (Toothed dock) and †¢ Melilotus indica L. (Sweet clover) The experimental area was free of noxious and perennial weed species. Treatments (Exp-1) †¢ Control (Un-weeded check) WE: Water extract Hand weeding at 60 days after sowing (DAS) †¢ Herbicide (Logron) @ 250 g ha-1 at 60 DAS †¢ Sorghum root WE spray @ 10 L ha-1 at 60 and 80 DAS †¢ Sorghum stem WE spray @ 10 L ha-1 at 60 and 8 0 DAS †¢ Sorghum leaf WE spray @ 10 L ha-1 at 60 and 80 DAS †¢ Sorghum stem + root WE @ 5+5 L ha-1 at 60 and 80 DAS †¢ Sorghum stem + leaf WE @ 5+5 L ha-1 at 60 and 80 DAS †¢ Sorghum root + leaf WE @ 5+5 L ha-1 at 60 and 80 DAS Treatments (Exp-2) WE: Water extract †¢ Control (Un-weeded check) †¢ Hand weeding at 50 and 80 DAS †¢ Sorghum mulch @ 5 Mg ha-1 (Soil incorporated) †¢ Sorghum mulch @ 10 Mg ha-1 Soil incorporated) †¢ Sorghum WE @ 10 L ha-1 at 50 DAS. †¢ Sorghum WE @ 10 L ha-1 at 50 and 80 DAS. †¢ Sorghum WE @ 20 L ha-1 at 50 DAS. †¢ Sorghum WE @ 20 L ha-1 at 50 and 80 DAS Treatments (Exp-3) †¢ Control (Un-weeded check) WE: Water extract †¢ Sunflower WE @ 20 L ha-1 at 50 DAS †¢ Sorghum WE @ 20 L ha-1 at 50 DAS †¢ Sunflower WE + sorghum WE @ 10 +10 L ha-1 at 50 DAS †¢ Sunflower WE @ 20 L ha-1 at 50 and 80 DAS †¢ Sorghum WE @ 20 L ha-1 at 50 and 80 DAS †¢ Sunflower WE + sorghum WE @ 10 + 10 L ha-1 at 50 and 80 DASResearch Methodology: Preparation of water extract †¢ Sunflower and sorghum plants were harvested at maturity, grains were separated and residue was sundried and chaffed with fodder cutter into 2 cm pieces. †¢ Chaffed residue was soaked in de-ionized water in 1:10 (1 kg each of herbage in 10 L of water) in separate containers for 24 h at room temperature to prepare water extract (WE) . †¢ WE from respective containers were obtained by filtering the mixture through a screen. The volume of respective filtrate was reduced twenty times by continuously boiling at 100 0C to prepare water extract (Cheema and Khaliq, 2000). Sowing and cultural practices †¢ Seedbed was prepared by giving four cultivations each followed by planking. †¢ Fertilizer @ 125- kg N and P2O5 ha-1 was applied at the time of seedbed preparation. †¢ Wheat cv. ‘Inqilab-91’ was seeded @125 kg ha-1 was during November with a single row hand drill in ro ws 30 cm apart. Layout design: RCBD with 4R; Eight rows 30 cm apart per treatment were maintained in plot size of 7. 0 x 2. 4 m. †¢ The wheat variety, sowing time, layout plan and other cultural practices were almost same for every year. Measures: Weeds †¢ Weed density †¢ Weed dry weight (biomass) Wheat †¢ Spike length (cm), †¢ Spikelets spike-1 †¢ Grains spike-1 †¢ Fertile tillers m-2 †¢ 1000-grain weight. Statistical analysis The data were subjected to analysis of variance technique. F-statistic was based on residual mean square error.The LSD at 5% level of probability was used for comparison of treatment means (Montgomery, 2001). RESULTS & DISCUSSION Experiment # 1 Phyto-toxic effects of root, stem and leaf water extract of mature sorghum on Weeds density & Dry weight Treatments Control (Un-weeded check) Hand weeding at 60 DAS Exp-1 Weed density ( m-2) 80 DAS 105 DAS Weeds dry weight (g m-2) 80 DAS 105 DAS 147 a 79 d (-46*) 132 a 78 f (-41) 36. 7 g (-72) 102 c (-22) 112 b (-15) 113 b (-14 88 e (-33) 94 de (-29) 102 cd (-23) 8. 52 2 a 12 e (-45) 5. 5 f (-75) 18 cd (-16) 20 b (-8) 20 b (-8) 17 d (-22) 17 cd (-20) 19 bc (-14) 1. 54 27 a 17 e (-38) 8. 77 f (-67) 21 c (-21) 24 b (-11) 23 b (-14) 18 e (-34) 20 d (-27) 27 c (-20) 1. 57 Herbicide (Logron) @ 250 g ha-1 34 e (-77) at 60 DAS Sorghum root WE spray @ 10 L 117 c (-21) ha-1 at 60 and 80 DAS Sorghum stem WE spray @ 10 L 129 b (-12) ha-1 at 60 and 80 DAS Sorghum leaf WE spray @ 10 L 127 b (-14) ha-1 at 60 and 80 DAS Sorghum stem + root [email  protected] 5+5 L 113 c (-23) ha-1 at 60 and 80DAS Sorghum stem + leaf [email  protected] 5+5 L 111 c (-24) ha-1 at 60 and 80 DAS Sorghum root + leaf WE @ 5+ 5 121 bc (-18) L ha-1 60 and 80 DAS LSD (0. 05) 10. 41 * Figures in parenthesis show % decrease in weed density/dry weight compared to control. Effect of root, stem and leaf water extract of mature sorghum on yield components and wheat grain yield Treatments Control (Un- weeded check) Tillers (m-2) Spike length (cm) Spikelet # spike-1 Grains # 1000-Grain spike-1 weight (g) Exp-1Grain yield (T ha-1) 345e Hand weeding at 60 DAS 396b Herbicide (Logron) @ 250 g 427a ha-1 at 60 DAS Sorghum root WE spray @ 10 L ha-1 at 60 and 80 DAS Sorghum stem WE spray @ 10 L ha-1 at 60 and 80 DAS Sorghum leaf WE spray @ 10 L ha-1 at 60 and 80 DAS Sorghum stem + root [email  protected] 5+5 L ha-1 at 60 and 80 DAS Sorghum stem + leaf [email  protected] 5+5 L ha-1 at 60 and 80 DAS Sorghum root + leaf WE @ 5+ 5 L ha-1 60 and 80 DAS LSD (0. 05) 9. 0e 10. 3abcd 11. 2a 10. 0bcde 9. 5de 9. 8cde 10. 9 ab 10. abc 10. 7 abc 1. 03 20. 7 21. 0 20. 9 21. 1 20. 5 21. 1 20. 2 21. 0 20. 2 – 41. 7c 47. 3ab 49. 4a 48. 8ab 47. 3ab 46. 1b 49. 0ab 48. 0ab 48. 0ab 3. 04 32. 5e 33. 7d 34. 6bc 35. 6a 33. 6d 33. 1de 36. 0a 33. 9cd 35. 2ab 0. 90 2. 76f 3. 2bc (+18) 3. 5a (+26) 3. 1cde (+12) 3. 0de 2. 9ef (+8) (+6) 365cde 353de 349e 357de 385bc 376bcd 54. 45 3. 3ab (+20) 3. 3abc (+19) 3. 2bcd (+14) 213. 2 * Figures in parenthesis show % decrease in weed density/dry weight compared to control.FINDINGS FROM EXPERIMENT # 1: †¢ Sorghum stem + root [email  protected] 5+5 L ha-1 at 60 and 80 DAS treatment caused 33% reduction in weed density and dry weight by about; †¢ This reduction was 41% in hand weeding and 72% by the application of Logron @ 250 g ha-1 at 60 DAS †¢ The increase in grain yield in stem + root and stem + leaf WE treatments were statistically same as in hand weeding and herbicide application. Cont†¦.. Experiment # 2 RESULTS & DISCUSSIONFINDINGS FROM EXPERIMENT # 2: †¢ Data showed that incorporation of sorghum herbage mulch @ 10 Mg ha-1 and twotimes sprays of Sorghum water extract @ 20 L ha-1 at 50 and 80 DAS decreased weeds density by about 42%, and weeds dry weight by 34%, respectively compared to control measured at 95DAS. †¢ Maximum increase (33%) in wheat grain yield was recorded in plots where two times Sorghum WE @ 20 L ha-1 was sprayed at 50 and 80 DAS over control. Cont†¦.. Experiment # 3 RESULTS & DISCUSSIONFINDING FROM EXPERIMENT # 3: †¢ Sorghum water extract was more effective than sunflower water extract and combination of both these extracts performed better than their sole application. Cont†¦.. CONCLUSION I. Stem + root water extract suppressed weed density by 33% over control i. e. about half of the effects of herbicide â€Å"Logron† application (72%) in wheat. The increase in grain yield in stem + root and stem + leaf WE treatments was statistically at par with hand weeding and herbicide application.Although root WE alone and in combination with stem or leaf WE was more effective in suppressing weeds and improving wheat yields but using whole plant sorghum herbage seems more practicable. II. Incorporation of sorghum herbage mulch @ 10 Mg ha-1 and two times sprays of sorghum WE @ 20 L ha-1 at 50 and 80 DAS decreased weeds density by about 42%, and weeds dry weig ht by 34%, respectively compared to control measured at 95 DAS. Maximum increase in wheat grain yield by 33% over control was recorded in plots where two times sorghum WE @ 20 L ha-1 was sprayed at 50 and 80 DAS.III. Sorghum WE was more effective than sunflower WE and mixture of sorghum and sunflower reduced weed density and weed dry weight by 27% and 26% over control respectively, and increased wheat yields by 48% over control. RECOMMENDATION †¢ The mixture of preceding allelopathic crop herbage use as mulch or water extract for weed management both for summer and winter crops need to be further investigated under different ecological zones of Pakistan. Muhammad Ashraf Professor of Agronomy [email  protected] com