EFFECT OF DURATION OF INCORPORATION OF COMMON SUNFLOWER (Helianthus annuus L.) LEAVES IN THE SOIL ON THE GERMINATION OF SELECTED WEEDS AND CROPS Mohammad Cholid Indonesian Tobacco and Fibre Crops Research Institute ABSTRACT Experiment were conducted with the following objectives : To determine the effect of length of incorporating common sunflower leaves in the soil on growth of itchgrass [Rottboellia. cochinchinensis (Lour)W.D. Clayton], barnyardgrass (Echinochloa glabrescens Munro ex Hook.f.), water purslane [Ludwigia octovalvis (Jacq.) Raven], mungbean (Vigna radiata L.), and rice (Oryza sativa L.). Treatments were replicated three times in a factorial completely randomized design. The first factor were species of crops/weeds: rice, mungbean, itchgrass, barnyardgrass, water purslane. The Second factor were duration of incorporation of common sunflower residues in soil: untreated, 0 day, 7 days, dan 14 days. The Result indicated that incorporation of common sunflower leaves in the soil at seeding (0 day) reduced seed germination and seedling growth of all test species. The leaves incorporated in the soil decreased germination and further growth of all test plant seedlings according to the duration of incorporation in the following order: 0 day (at seeding) > 7 days before seeding > 14 days before seeding. Incorporated common sunflower leaves in the soil had inhibitory potential on water purslane and itchgrass, but less or no inhibition on rice and mungbean. It may be inferred that common sunflower leaves may be used for effective itchgrass and water purslane controls, without damaging mungbean and rice plants. Barnyardgrass was affected by leaf residues only at germination and initial growth, but less affected at further growth stage. Key word: Allelopathic, Helianthus annuus L, crops, weeds ABSTRAK Pengaruh lama pencampuran residu daun bunga matahari (Helianthus annuus L.) dalam tanah pada perkecambahan beberapa tanaman dan gulma. Penelitian ini bertujuan untuk mengevaluasi pengaruh lama pencampuran residu dari daun tanaman bunga matahari dengan tanah terhadap pertumbuhan Rottboellia cochinchinensis (Lour)W.D. Clayton, Echinochloa glabrescens Munro ex Hook.f., Ludwigia octovalvis (Jacq.) Raven, kacang hijau (Vigna radiata L.), dan padi (Oryza sativa L.). Rancangan Percobaan yang digunakan adalah Rancangan Acak Kelompok Faktorial, dengan 3 ulangan. Faktor pertama adalah spesies tanaman dan gulma yaitu: padi, kacang hijau, Rottboellia. Cochinchinensis, Echinochloa glabrescens, dan Ludwigia octovalvis. Faktor kedua adalah lama pencampuran yaitu : tanpa residu; 0 (saat tanam), 7 hari sebelum tanam (hbt), 14 hbt. Hasil percobaan menunjukkan bahwa pencampuran 1
residu daun tanaman bunga matahari saat tanam (0 hbt) menghambat perkecambahan dan pertumbuhan semua tanaman yang diuji. Derajat penghambatan perkecambahan dan pertumbuhan terhadap tanaman yang diuji secara berurutan: 0, 7, 14 hari sebelum tanam. Perkecambahan, serta pertumbuhan tunas dan akar padi lebih sensitif terhadap larutan ekstrak daun bunga matahari dibanding kacang hijau. Residu daun bunga matahari menghambat perkecambahan dan pertumbuhan tanaman lebih besar pada Ludwigia octovalvis, Rottboellia. Cochinchinensis dibanding pada tanaman (padi dan kacang hijau). Hal ini menunjukkan bahwa residu daun dari tanaman bunga matahari efektif untuk mengendalikan gulma Ludwigia octovalvis, Rottboellia. Cochinchinensis, dengan tanpa menimbulkan kerusakan pada tanaman kacang hijau, serta sedikit penghambatan pada tanaman padi. Kata kunci : Alelopati, Helianthus annuus L, tanaman, gulma INTRODUCTION Modern agriculture is commercial and target-oriented and hence in order to achieve enhanced production, large amount of synthetic herbicides are used to control weeds (Batish et al., 2001). In order to maintain the sustainability of the agro-ecosystems, it is essential to explore eco-friendly means of alternative weed management. Allelopathy is one of the promising alternatives which are being manipulated for getting benefits of weed management through various strategies. These activities have shown significant prospects for allelopathy being utilized for increasing crop productivity and quality of food for humans, decreasing our reliance on synthetic pesticides and improving the ecological environment. Recent research has demonstrated possibilities of such prospects in reality, especially in weed control. In higher plants allelochemicals are released from plants through (a) volatilization (b) leaf or stem leachates, (c) root exudates and (d) decomposition of plant residues (Rice, 1984). Allelopathic effects of residues of sunflower have been studied on the germination, growth and yield of other crops. Soil incorporation of its residues at 2g/80g soil inhibited seed germination and seedling growth of sorghum. Germacranolide isolated from sunflower inhibited the growth of oat coleoptiles (Spring and Hager, 1982). Studies have shown that common sunflower has allelopathic properties on some plant species. It s inhibiting property has been tested on several weeds such as jungle rice (Echinochloa colona L.) (Abeysekara, 1992), Trianthema portulacastrum L., Parthenium hysterophorus L, and Amaranthus viridis L. (Dharamraj, 1998), but not on 2
other weed species especially major weeds in the Philippines. Further tests on major weeds in major crops need to be conducted. The study aimed to determine the allelopathic effect of common sunflower through soil incorporated leaves on the germination and further seedling growth of itchgrass (Rottboellia. cochinchinensis (Lour)W.D. Clayton), barnyardgrass (Echinochloa glabrescens Munro ex Hook.f.), water purslane (Ludwigia octovalvis (Jacq.) Raven), mungbean (Vigna radiata L.), and rice (Oryza sativa L.). MATERIALS AND METHODS Experiments were conducted from April 2003 to September 2003, at the Central Experiment Station, Department of Agronomy, U.P. Los Baños, College of Agriculture, Laguna, Philippines. Mature seeds of itchgrass (R. cochinchinensis (Lour) W.D. Clayton), barnyardgrass (Echinochloa glabrescens Munro ex Hook.f.), water purslane (Ludwigia octovalvis (Jacq.) Raven) were collected from farms in Los Baños. Common sunflower (Helianthus annuus L.) and rice (Oryza sativa L.) var. PSB PC-74 seeds were obtained from the UPLB Central Experiment Station, and mungbean (Vigna radiata L.) var. MG 50-10A seeds were obtained from the Bureau of Plant Industry. All seeds were sun-dried and stored in a closed container at room temperature prior to use. All test plants were tested for germination in petridishes at laboratory condition prior to the experiment. This was to make sure that in all species, germination was above 75%. Several kinds of seed treatments were tried to improve seed germination. For example, itchgrass seeds after 6 months of storage were heated in an oven at 70 o C for 4 hours, then a cut was made on both sides of the seed cover before germinating under laboratory room condition. Common sunflower plants, which were grown at the UPLB Central Experimental Station were harvested at the start of flowering. Common sunflower leaves were cut and chopped into 2 to 3 cm pieces and uniformly incorporated in soil for a length of 0, 7 and 14 days in plastic pots. The plastic cups contained 450 grams of thoroughly mixed upland soil for mungbean and itchgrass as test plants and lowland soil for rice, barnyardgrass and water purslane as test plants. These soils were collected from 0-15 cm 3
depth from a uniform location in the lowland and upland areas, at the Central Experiment Station, Department of Agronomy, U. P. Los Baños. Based on result of previous experiment, concentration 1:16 (w/v) was selected for further study. This is equivalent to one gram common sunflower leaves for every 16 grams soil (1:16 w/w) or equal to 28.125 g leaves per 450 g soil. Leaf residues were incorporated in the soil in 12 cm diameter plastic cups for different durations before sowing the test plants. Ten seeds of test crops (rice and mungbean) and 20 seeds of test weeds (itchgrass, barnyardgrass and water purslane) were sown at the same time in the cups as indicated under treatment and experiment design. design. Treatments were replicated three times in a factorial completely randomized The first factor were species of crops/weeds: rice, mungbean, itchgrass, barnyardgrass, water purslane. The Second factor were duration of incorporation of common sunflower residues in soil: untreated, 0 day, 7 days, dan 14 days. Distilled water was added to maintain field capacity of the soil in the cups. The plants were kept in the greenhouse. The number of germinated seeds was counted 8-10 days after sowing (DAS). Seedlings were thinned to two per cup at 10 DAS, and plants were watered as needed. Plant height, number of leaves produced, number of tillers or branches were recorded at weekly intervals for 4 weeks after seedling emergence. At 28 days after planting, the plants were slowly pulled from the soil with the aid of water and placed on the screen. The roots were washed free of soil and plants were separated into shoots and roots. The samples were dried at 80 o C for 48 hours in an oven and dry weights were recorded. RESULTS AND DISCUSSION Seed Germination Common sunflower Leaves incorporated into the soil significantly inhibited germination of rice, itchgrass, barnyardgrass and water purslane, but not mungbean. The effect of the duration of leaf incorporation in the soil on germination of the crops and weeds are shown in Table 1. Germination of rice was inhibited at seeding (zero day) of soil incorporation (Table 1). Germination of rice was highest in the untreated (93.33%). Leaf incorporation 4
for 0, 7, 14 days did not significantly affect rice germination, but percent germination were significantly lower than the untreated where there were no leaves incorporated. Mungbean seed germination, however, was not affected by the common sunflower leaves at all durations of incorporation. Table 1. Effect of duration of leaf incorporation in soil on germination of rice, mungbean, itchgrass, barnyardgrass and water purslane seeds DURATION RICE MUNG- BEAN ITCHGRASS BARNYARD- GRASS W.PURS- LANE % Germination Untreated 93.33a 93.33a 75.00a 76.67a 83.33a 0 day 75.00b 83.33a 26.67c 28.33c 8.33c 7 days 78.33b 83.33a 51.67b 46.67b 35.00bc 14 days 85.00ab 90.00a 60.00ab 53.33b 50.00ab % Inhibition over the untreated Untreated 0 0 0 0 0 0 day 19.64 10.71 64.44 63.05 90.00 7 days 16.07 10.71 31.11 39.13 58.00 14 days 8.93 3.57 20.00 30.44 40.00 Number followed by the same letters in each column are not significantly different at 1% LSD Germination of the test weed species was markedly inhibited by leaves incorporated in the soil. The pattern of germination of the test weed species was similar. The shorter the duration of leaf incorporation in soil (0 day), the lower, the percent germination. Water purslane showed the most inhibition, followed by barnyardgrass and itchgrass. As the duration of incorporation was prolonged percent germination of the weeds increased. This result suggests that leaves of common sunflower were more inhibitory when freshly incorporated, and that the inhibitory principle might have been altered during incorporation in soil and with time. As compared with the test crop species, the weed test species were more sensitive to the inhibitory effect of the common sunflower leaves. Plant Height The effect of duration of leaf incorporation in soil on plant height of rice, mungbean, itchgrass, barnyardgrass and water purslane at 28 DAS is shown in Table 2. 5
Plant height of all test species was significantly reduced, regardless of duration of incorporation of leaves. Between the crop species, plant height of rice was more inhibited than that of mungbean, suggesting that mungbean was less sensitive to the incorporated leaves of common sunflower. Such result agrees with that on the germination effect of the leaf aqueous extracts on mungbean in the first experiment. Table 2. Effect of duration of leaf incorporation in soil on plant height of rice, mungbean, itchgrass, barnyardgrass and water purslane at 28 DAS DURATION RICE MUNG- BEAN ITCH-GRASS BARNYARD- GRASS W.PURS- LANE Plant height (cm) Untreated 50.92a 30.88a 64.95a 62.83a 16.92a 0 day 25.77c 19.57b 13.05d 19.45c 0.45c 7 days 36.83b 21.17b 24.35c 52.72ab 1.82bc 14 days 40.48b 23.18ab 35.13b 47.22b 4.65b % Inhibition over the untreated Untreated 0 0 0 0 0 0 day 49.39 36.63 79.91 69.04 97.34 7 days 27.67 31.44 62.51 16.09 89.24 14 days 20.50 24.94 45.91 24.84 72.52 Numbers followed by the same letters in each column are not significantly different at 1% LSD Plant height of the weed test species was markedly inhibited by leaves incorporated in soil. The pattern of inhibition was similar for all the weed test species. Water purslane, however exhibited the greatest reduction followed by itchgrass and barnyardgrass at all durations of incorporation of leaves in the soil (Table 2). Among the test species, the weed test species were greatly inhibited by leaves incorporated in soil than the crop test species at all durations of incorporation. The reduction in plant height of test species due to the incorporated leaves compared to the untreated may be due to the presence of allelochemicals in the common sunflower leaves. Growth suppression may result from action of known allelochemicals like coumarin or phenolic acid derivatives (Einhellig and Kuan, 1971). Negative effect of sunflower on other crops may be due to the biochemical interference of allelopathy (Iron and Burnside, 1982; Schon and Einhellig, 1982). Figures 1, dan 2 illustrate this inhibition in seedlings of rice, mungbean, itchgrass, barnyardgrass, and water purslane as affected by the duration of incorporation in the soil of the common sunflower leaves. 6
Figure 1. Effect of incorporated common sunflower leaves on rice and mungbean at 14 days after seeding. Figure 2. Effect of incorporated common sunflower leaves on itchgrass and barnyardgrass at 14 days after seeding Figure 3. Effect of incorporated common sunflower leaves on water purslane at 14 days after seeding 7
Plant Dry Weight Dry weight of all test species was significantly reduced, regardless of duration of incorporation of common sunflower leaves in soil (Table 3). Leaf incorporation at seeding had greater inhibitory effect than that at 7 days and 14 days before seeding. Shoot and root dry weights of both crop species were reduced at seeding (0 day) i.e. rice (0.60 g/pot and 0.14 g/pot) and those of mungbean (0.57g/pot and 0.10 g/pot), however these were not significantly different from those at 7 days and 14 days before seeding. This again suggests that freshly incorporated residues were more inhibitory than those residues made to decompose for 7 and 14 days. It may be inferred that the inhibitory materials have undergone some transformation as incorporation in the soil was prolonged. Table 3. Effect of duration of leaf incorporation in soil on shoot and root dry weights of rice, mungbean, itchgrass, barnyardgrass and water purslane DURATION DRY WEIGHT (g/pot) Rice Mungbean Itchgrass Barnyardgrass W.purslane Shoot Untreated 3.06a 1.52a 5.51a 3.16a 0.65a 0 day 0.60b 0.57b 0.08c 0.20c 0.00c 7 days 0.64b 0.60b 0.49b 1.79b 0.02bc 14 days 0.86b 0.58b 0.56b 1.83b 0.18b Root Untreated 1.60a 0.37a 2.80a 2.32a 0.26a 0 day 0.14c 0.10b 0.11c 0.08c 0.00b 7 days 0.30bc 0.10b 0.36bc 1.05b 0.02b 14 days 0.45b 0.09b 0.49b 0.91b 0.03b Numbers followed by the same letters in each column are not significantly different at 5% LSD Shoot and root dry weights of the weed species were markedly reduced by common sunflower leaves incorporated in the soil. The pattern of reduction in shoot and root dry weights of the weed test species was similar. The shorter the duration of incorporation in soil, the lower the shoot and root dry weights. As incorporation was prolonged for 7 and 14 days the greater the dry weight. Water purslane shoot and root lengths were completely inhibited (100%) by leaf residues incorporated at seeding. These studies show that leaves of common sunflower were more inhibitory to the weed test species than to the crop test species. 8
This result suggests that leaves of common sunflower were more inhibitory when freshly incorporated and that the inhibitory substances may have been altered during incorporation in soil. Narwal et al. (1999) reported that with delay in sowing of succeeding crops after sunflower harvest, the magnitude of inhibitory effect decreases. As in the germination tests, sunflower leaves incorporated in soil also inhibited shoot and root dry matter (DM) in seedlings of test crops. These results also indicate that there is some selectivity in the action of the inhibitory substances. Crop test species (rice and mungbean) were less sensitive to leaves incorporated in the soil than weed test species (itchgrass, barnyardgrass, and water purslane). Similar findings of Steinsiek et al. (1982), indicated that inhibition of weed seed germination and further seedling growth are dependent on the species tested (Kalita and Dey, 1998). These results parallel previous studies by Narwal et al. (1999b), who reported that soil with sunflower residues tested after harvest inhibited the germination of summer crops sown immediately (within 9 days) after incorporation. Incorporation of leaves in the soil reduced shoot and root dry weights of all test species. This may be due to the inhibitory effect of allelochemicals on mineral uptake and translocation (Glass, 1973). Sowing the test crops 36 days after incorporation, no inhibition was observed, rather germination was stimulated. It may be probable that during this period, toxic allelochemicals have been decomposed or transformed to non-toxic compounds. In a similar finding, Dharmaraj (1998a) reported that when cotton was sown between 3-8 weeks after leaf litter of sunflower incorporation, germination was not reduced but dry matter was increased. Bell and Koeppe (1972) found that oxygen uptake by excised corn roots was inhibited by more than 90% due to the reduced absorption and higher respiration rates. This led to the depletion of photosynthates used by the growing seedling. The overall effect was reduced growth and less dry mater accumulation by the indicator plants. The presence of allelopathic phytotoxins in the residues incorporated is a logical explanation for the growth reductions. One mechanism of toxic action on seedlings involves an interference with water balance. Such effects on water balance may result from the action of known allelochemicals like coumarin or phenolic acid derivatives. Stomata closure has been reported following applications of scopoletin and chlorogenic, 9
caffeic, p-coumaric, ferulic, and tannic acids (Einhellig and Kuan, 1971). Patterson (1981) reported that t-cinnamic, p-coumaric, vanillic, caffeic, ferulic, and gallic acids severely reduced photosynthetic rate in soybean (Glycine max [L.] Merr.). Reduction in photosynthesis was associated with reduced stomatal conductance. Soybean treated with caffeic, ferulic, and gallic acids also had a significant depression of leaf water potential. Phenols are common secondary plant metabolites involved in such phytotoxic activity, as they occur in higher concentrations in plant tissues and soil. The phenolic acids affect seed germination, radicle and plumule elongation and dry matter accumulation in many crop species (Gogoi et al., 2000). CONCLUSION Incorporation of common sunflower leaves in soil at seeding (0 day) reduced seed germination and seedling growth of all test species. Prolonging the duration of incorporation i.e. 14 days before seeding had less or no effect on germination, and shoot and root dry weight of the test species. The shorter the duration of incorporation of common sunflower leaves in the soil, the higher the inhibitory effect to the test plants. The leaf residues incorporated in the soil decreased germination and further growth of all test plant seedlings according to the duration of incorporation in the following order: 0 day (at seeding) > 7 days before seeding > 14 days before seeding. Results indicated that incorporated common sunflower leaves in the soil had inhibitory potential on water purslane and itchgrass, but less or no inhibition on rice and mungbean. It may be inferred that common sunflower leaves may be used for effective itchgrass and water purslane controls, without damaging mungbean and rice plants. 10
LITERATURE CITED ABEYSEKERA, S.K. M.M.A. 1992. comparative study on agronomic characters and allelopathic activity of common sunflower (Helianthus annuus L.) and wild sunflower (Tithonia diversifolia (Herm SL.) Gray). MS Thesis. University of the Philippines at Los Baños. Philippines. 71p. BATISH, D.R., H.P. SINGH and R.K. KOHLI. 2001. Allelopathy as a tool for sustainable weed management. The Proceeding of the 18 th Asian-Pacific Weed Science Society Conference. May 28- June 2, 2001. Beijing, P.R. China. pp. 168-173. BELL, D.T. and KOEPPE. 1972. Non competitive effects of giant foxtail on growth of corn. Agron. J. 64:321-325. DHARMARAJ, G. 1998a. Allelopathic influence of sunflower on field crops. abstracts. Allelopathy Journal 6(1).pp.103. EINHELLIG, F.A. and L. KUAN. 1971. Effects of scopoletin and chlorogenic acid on stomata aperture in tobacco and sunflower. Bull. Torrey Bot. Club 98 : 155-162. GLASS, A.D.M. 1973. 1973. Influence of phenolic acids on ion uptake. Plant Physiology 51: 1037-1041. GOGOI, B., KAUSHIK DAS and K.K. BARUAH. 2000. Effcet of allelochemicals on germination and seedling growth of rice (Oryza zativa L.) cultivars. Allelopathy Journal 7 (2): 279-284. IRONS, M.S. and C.V. BURNSIDE. 1982. Competitive and allelopathic effects of sunflower. Weed Science 30:372-377. KALITA, D., H. CHOUDHARY and S.C. DEY. 1999. Assessment of allelopathic potential of some common upland rice weed species on morphophysiological properties of rice (Oryza sativa L.) plant. Crop research 17: 41-45. KOEPPE, D. E., L. M. ROHRBAUGH, E. L. RICE and S.H. WENDER. 1970. Tissue age and caffeoylquinic acid concentrations in sunflower, Phytochemistry 9:297-301. NARWAL, S.S., YADAVA, S. and S. GUPTA. 1999a. Allelopathic effects of sunflower on succeeding summer crops. 1. Field studies and bioassays. Allelopathy Journal 6:35-48. NARWAL, S.S., T. SINGH, J.S. HOODA and M.K. KATHURIA. 1999b. Allelopathic effects of sunflower on succeeding summer crops. 2. Pot culture and biomass decomposition. Allelopathy Journal 6:209-226. PATTERSON, D.T. 1981. Effects of allelopathic chemicals on growth and physiological responses of soybean (Glycine max). Weed Sci. 29:53-58. RICE, E.L. 1984. Allelopathy (second edition). Academic Press, Orlando. p. 29-30. In 11
SPRING, O. and A. HAGER. 1982. Inhibition of elongation growth by two sesquiterpene lactones isolated from Helianthus annuus. Peredovick. Pergamon. Phytochemistry, 21 : 2551-2553. STEINSIEK, J.W., L.R. OLIVER and F.C. COLLINS. 1982. Allelopathic potential of wheat straw on selected weed species. Weed Science. 30: 495-497. 12