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Kerala Agricultural University, Thrissur
The history of agricultural education in Kerala can be traced back to the year 1896 when a scheme was evolved in the erstwhile Travancore State to train a few young men in scientific agriculture at the Demonstration Farm, Karamana, Thiruvananthapuram, presently, the Cropping Systems Research Centre under Kerala Agricultural University. Agriculture was introduced as an optional subject in the middle school classes in the State in 1922 when an Agricultural Middle School was started at Aluva, Ernakulam District. The popularity and usefulness of this school led to the starting of similar institutions at Kottarakkara and Konni in 1928 and 1931 respectively.
Agriculture was later introduced as an optional subject for Intermediate Course in 1953. In 1955, the erstwhile Government of Travancore-Cochin started the Agricultural College and Research Institute at Vellayani, Thiruvananthapuram and the College of Veterinary and Animal Sciences at Mannuthy, Thrissur for imparting higher education in agricultural and veterinary sciences, respectively. These institutions were brought under the direct administrative control of the Department of Agriculture and the Department of Animal Husbandry, respectively. With the formation of Kerala State in 1956, these two colleges were affiliated to the University of Kerala. The post-graduate programmes leading to M.Sc. (Ag), M.V.Sc. and Ph.D. degrees were started in 1961, 1962 and 1965 respectively.
On the recommendation of the Second National Education Commission (1964-66) headed by Dr. D.S. Kothari, the then Chairman of the University Grants Commission, one Agricultural University in each State was established. The State Agricultural Universities (SAUs) were established in India as an integral part of the National Agricultural Research System to give the much needed impetus to Agriculture Education and Research in the Country. As a result the Kerala Agricultural University (KAU) was established on 24th February 1971 by virtue of the Act 33 of 1971 and started functioning on 1st February 1972. The Kerala Agricultural University is the 15th in the series of the SAUs.
In accordance with the provisions of KAU Act of 1971, the Agricultural College and Research Institute at Vellayani, and the College of Veterinary and Animal Sciences, Mannuthy, were brought under the Kerala Agricultural University. In addition, twenty one agricultural and animal husbandry research stations were also transferred to the KAU for taking up research and extension programmes on various crops, animals, birds, etc.
During 2011, Kerala Agricultural University was trifurcated into Kerala Veterinary and Animal Sciences University (KVASU), Kerala University of Fisheries and Ocean Studies (KUFOS) and Kerala Agricultural University (KAU).
Now the University has seven colleges (four Agriculture, one Agricultural Engineering, one Forestry, one Co-operation Banking & Management), six RARSs, seven KVKs, 15 Research Stations and 16 Research and Extension Units under the faculties of Agriculture, Agricultural Engineering and Forestry. In addition, one Academy on Climate Change Adaptation and one Institute of Agricultural Technology offering M.Sc. (Integrated) Climate Change Adaptation and Diploma in Agricultural Sciences respectively are also functioning in Kerala Agricultural University.
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ThesisItem Open Access Crop establishment methods and weed management on productivity of cowpea [Vigna unguiculata (L.)Walp.](Department of Agronomy, College of Agriculture,Vellanikkara, 2022-04-27) Ayisha Jezla, P; Anitha,S; KAUCowpea is an important pulse crop grown throughout India and Kerala as a grain and vegetable crop. Weeds possess severe problem in the early growth stages of cowpea due to wider spacing and low initial growth and resulted in yield reduction. Hence the crop requires to be kept weed free particularly during the initial 6-8 weeks, ie the critical period of competition. The present study was carried out with the objective to enhance the productivity of cowpea grown under different crop establishment methods by adopting proper weed management measures. Field experiment was conducted from October to December 2020 at the Department of Agronomy, College of Agriculture, Vellanikkara. The experiment was laid out with factorial RBD with two factors replicated thrice. Factor A with two methods of establishments such as broadcasting and line sowing. Factor B with six weed management practices such as hand weeding @ 20 and 40 DAS , imazethapyr + imazamox, 40 g/ha @ 15-20 DAS , imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS, imazethapyr, 40 g/ha @ 15- 20 DAS, imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS and unweeded control. Cowpea variety PGCP-6 was used as test crop. Results revealed that methods of crop establishment had significant effect on weed density, growth parameters and yield attributes of cowpea. Line sowing resulted in 39% and 31% reduction in weed count and weed dry weight. Weed control efficiency and yield was 14% and 3% higher compared to broadcasting. The lowest weed count, weed dry weight and higher weed control efficiency was recorded in hand weeding at 20 and 40 DAS. The lowest weed index was observed in imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS Application of imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding at 40 DAS resulted in taller plants. At 30 DAS higher LAI was noted in imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS. Imazethapyr, 40 g/ha @15- 20 DAS recorded higher LAI at 40 DAS.The highest dry matter production was recorded in imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS. Application of imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding imazethapyr, 40 g/h registered significantly higher number of pods per plant and pod weight. Number of seeds per pod and 100 grain weight was higher in imazethapyr, 40 g/ha @15- 20 DAS fb hand weeding @ 40 DAS. The highest yield was recorded from plots where two hand weeding were conducted (937.67 kg/ha), followed by imazethapyr + imazamox, 40 g/ha @15- 20 DAS fb hand weeding (877.30 kg/ha). Line sown cowpea received two hand weeding recorded higher yield (923.67 kg/ha) compared to other treatment combinations. Adoption of weed management practices resulted in 70 % higher yield in cowpea. Nitrogen uptake by crop was higher in imazethapyr 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS, which was on par with hand weeding twice. Broadcasted plot, where two hand weeding were conducted recorded higher N uptake by crop. Higher P uptake was noticed in hand weeding @ 20 and 40 DAS. Higher soil N availability was observed in imazethapyr + imazamox 40 g/ha @ 15- 20 DAS and P availability was higher in imazethapyr + imazamox, 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS. Among crop establishment methods higher net return and B:C ratio was observed in broadcast sowing compared with line sown cowpea. The highest net return (Rs. 102861) and B:C ratio (2.45) was registered in imazethapyr + imazamox @ 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS. Results of the study indicated that application of imazethapyr + imazamox, 40 g/ha @ 15- 20 DAS fb hand weeding @ 40 DAS can be recommended as a cost effective weed management practice for broadcasted and line sown cowpea.ThesisItem Open Access Integrated nutrient management in minisett cultivation of elephant foot yam {Amorphophallus paeoniifolius (Dennst.) Nicolson}(Department of Agronomy, College of Agriculture, 2022) Dhanalakshmi V N.; Rajasree GThe study entitled “Integrated nutrient management in minisett cultivation of elephant foot yam [Amorphophallus paeoniifolius (Dennst.) Nicolson]” was conducted at the Instructional Farm, College of Agriculture, Vellayani, Thiruvananthapuram to standardise the minisett size in elephant foot yam and to investigate the effect of integrated nutrient management practices on growth, yield, quality and economics of cultivation and to study the rooting and tuberisation pattern of minisett planted elephant foot yam. The investigation consisted of two experiments; standardisation of minisett corm size and integrated nutrient management practices (field experiment) and rooting and tuberisation pattern study (pot culture) and was undertaken during April to November 2018 and 2019. The first experiment was laid out in RBD with 15 treatment combinations and a control, replicated thrice. The treatments comprised three minisett corm sizes (s1-200 g, s2-300 g and s3-400 g) and five integrated nutrient management practices (i1-100 per cent NPK, i2-75 per cent NPK with 50 per cent N substitution through coir pith compost, i3-75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF, i4-50 per cent NPK with 50 per cent N substitution through coir pith compost, i5-50 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF). The minisett corms and control corms (1 kg) of elephant foot yam var. Gajendra were planted at a spacing of 60 x 60 cm and 90 x 90 cm respectively. The recommended dose of N, P and K (100:50:150 kg NPK ha-1 ) for elephant foot yam was modified based on soil test data. Substitution of N with coir pith compost was carried out on N equivalent basis, and P and K were given through chemical sources. The pot culture experiment was laid out in CRD with 14 plants per treatment with the same treatments as the field experiment. The number of days taken for 100 per cent sprouting of seed corms varied between minisett corms and control corms and the latter sprouted early. The minisett corm s3 (400 g) recorded taller plants, higher leaf area index, pseudostem 281 girth and canopy spread. Application of 100 per cent NPK (i1) as chemical fertilizer produced taller plants and higher canopy spread during later stages compared to INM practices. Among the INM treatments, i3 (75 % NPK with 50 % N substitution through coir pith compost + PGPR mix-I + AMF) found superior with respect to growth attributes such as plant height and canopy spread. The treatment combination s3i1 (400 g + 100 % NPK as chemical fertilizer) produced taller plants and recorded higher canopy spread. Among the interactions including INM practices, taller plants were produced by s3i3 and s3i5 and higher canopy spread was recorded with s3i2, s3i3 and s3i5. Control plants (1 kg) showed taller plants, higher pseudostem girth and canopy spread at all stages of observation. The s3 recorded higher yield attributes, corm yield (48.81 and 50.57 t ha-1 during first year and second year, respectively) and pooled corm yield (49.69 t ha1 ). The treatments, i1 (100 % NPK) recorded significantly the highest yield attributes and yield. Among the different INM practices, i3 recorded higher yield attributes and corm yield (38.26 and 45.37 t ha-1 during first year and second year, respectively), while corm yield in pooled mean analysis (41.82 t ha-1 ) was also higher in this treatment. The s3i1 (400 g + 100 % NPK as chemical fertilizer) produced significantly the highest yield attributes and yield among all the treatments. Among the INM combinations, s3i3 recorded higher yield attributes, corm yield and higher pooled mean of corm yield (51.29 t ha-1 ). Control recorded higher yield attributes than minisetts. Pooled analysis of corm yield ha-1 indicated that s3i1, s3i2, s3i3 and s3i5 were superior to control and s2i1, s2i2, s2i3 and s3i4 were on par with control. Quality attributes like starch, total sugar, crude protein and crude fibre content of corm were non significant with respect to the treatments. Higher dry matter content was obtained in i4 (50 % NPK with 50 % N substitution through coir pith compost). The lower content of oxalic acid was recorded with i5 and i4 and the higher content was in i1 (100 % NPK). The minisett corm s3 recorded superior results for nutrient content, uptake and nutrient harvest indices. The INM treatment, i3 recorded higher nutrient content and uptake, however the highest was recorded in i1 among all the treatments. The treatment s3i1 (400 g + 100 % NPK 282 through chemical fertilisers) recorded significantly the highest K uptake. Among the combinations including INM practices, s3i3 recorded higher K uptake during second year. The combinations, s3i1, s3i2, s3i3, s3i4 and s3i5 were found superior to control in case of nutrient uptake. Soil chemical properties after the field experiments were not significantly affected by the treatments. The treatment s3i1 (400 g + 100 % NPK) recorded the highest net income and BCR during both the years. The highest net income and BCR were recorded from s3i2 during first year and s3i3 during second year, and the two year mean of net income and BCR were also highest in the case of INM treatment s3i3. In pot culture study, chemical properties of potting medium at monthly intervals up to harvest were not significantly affected by the treatments except for organic carbon content. The treatment i3 (75 % NPK with 50 % N substitution through coir pith compost + PGPR mix-I + AMF) recorded higher organic carbon content at 5 MAP. The minisett corm s3 excelled in rooting pattern and root anatomical parameters. Higher number of roots per plant was recorded in i2 and i3, however, these treatments were on par with i1 (100 % NPK). Higher weight of roots per plant was observed in i5, i4 and i3 and, root anatomical parameters were superior in i3. The interactions, s3i5, s3i4 and s3i3 recorded the highest weight of roots per plant. Higher root parameters were recorded in control than in minisetts and, in case of number of roots per plant s3i1, s3i2 and s3i3 at 4, 6 MAP and harvest, and s3i1 at 5 MAP recorded on par results with control. In the case of weight of roots per plant, s3i3 was on par with control at harvest. The roots of plants applied with AMF showed mycelial network from 3 MAP up to the harvest, and in the maximum growing stage of 5 MAP, vesicles were found in between the cells of the roots of AMF applied plants. Higher root colonization was observed in s3i3 at 5 MAP. Corm initiation was observed between 1 MAP and 2 MAP in control and between 2 MAP and 3 MAP in all other treatments. The s2 (300 g) during 3-4 MAP and s3 (400 g) during all other stages had significantly the highest corm bulking rate (CBR). Higher corm bulking efficiency (CBE) was recorded in s2 during 3-4 MAP, s1 during 4-5 MAP and 6 MAP-harvest and s3 during 5-6 MAP. 283 The INM treatment i3 showed superior results for CBR and CBE, however, higher CBR and CBE were recorded in i1 (100 % NPK) among all the treatments. The s3i1 (400 g + 100 % NPK)showed the highest CBR and CBE during 4-5 MAP and 5-6 MAP among all the treatments. Among the INM interactions, s3i3 during 3-4 MAP and 5-6 MAP; s3i2 during 4-5 MAP and s3i4 during 6 MAP-harvest recorded higher CBR. The s2i3 during 3-4 MAP, s1i3 during 4-5 MAP, s3i3 during 5-6 MAP and s1i5 during 6 MAP-harvest recorded higher CBE. Higher corm weight per plant was recorded with s3. The i1 recorded the higher corm weight per plant among all the treatments, and at 5 MAP, i1 was on par with i3. Among the INM treatments i2 at 3 MAP and i3 at all other stages recorded higher corm weight per plant. Among interactions, s3i3 produced higher corm weight, however, among all the treatments the highest corm weight was noted in s3i1 at all stages except at 4 MAP. Control produced significantly higher corm weight per plant than minisetts. Uptake of nitrogen at 3 MAP and uptake of phosphorus at harvest were higher in s3. The INM treatment i3 recorded higher microbial population and dehydrogenase activity in the potting medium and among the interactions, higher dehydrogenase activity was recorded with s3i3. Significant and positive correlations were observed between corm weight per plant vs. root anatomical parameters and nutrient uptake vs. root anatomical parameters. It is evident from the present study that planting of 400 g minisett corm resulted in better growth, yield and quality of elephant foot yam. Application of 75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I [@ 10 g per pit (dry cow dung: PGPR mix-I in 50:1 proportion) - at planting and 2 MAP] + AMF (@ 10 g per pit - at the time of planting) in elephant foot yam resulted in superior growth, yield and quality under INM system. Planting of 400 g minisett and application of 75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF under an INM system could be recommended for economic production of minisett elephant foot yam. Rooting and tuberisation of elephant foot yam were found superior in planting of 400 g minisett corm with application of 75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF.ThesisItem Open Access Resource management for source- sink modulation in chinese potato[Plectranthus rotundifolius (Poir.) Spreng.](Department of Agronomy, College of Agriculture, Vellayani, 2022-01-20) Arunjith, P; Sheeba, Rebecca IsaacThesisItem Open Access Organic nutrition in taro (Colocasia esculenta (L.) Schott)(Department of Agronomy, College of Agriculture, Vellayani, 2022) Limisha, N P; KAU; Rajasree, GThe study entitled “Organic nutrition in taro (Colocasia esculenta (L.) Schott)” was conducted at College of Agriculture, Vellayani, Thiruvananthapuram, Kerala to investigate the effect of organic nutrition on growth, yield, quality, soil organic carbon build up and economics of cultivation of taro and to study rooting and tuberisation pattern of taro under organic nutrition. The experiment was conducted in the farmer’s field at Peringamala, Thiruvananthapuram from June 2019 to January 2020 and June 2020 to January 2021. The investigation comprised two separate experiments: (1) Organic nutrition in taro (field experiment) and (2) Rooting and tuberisation pattern study in taro (pot culture). The first experiment was laid out in randomized block design with three replications. The treatments comprised six organic sources (s1- FYM + wood ash; s2- FYM + wood ash +PGPR mix I; s3- FYM + wood ash + PGPR mix I + vermiwash; s4- poultry manure + wood ash ; s5- poultry manure + wood ash + PGPR mix I; s6- poultry manure + wood ash + PGPR mix I + vermiwash) and two in situ green manuring (g1- in situ green manuring with cowpea; g2- in situ green manuring with daincha) with three controls (C1- nutrient management through chemical fertilizers as per KAU POP (80 : 25: 100 kg ha-1 ); C2 - nutrient management as per KAU organic POP (Ad hoc); C3 - absolute control). The tuberization study was laid out as completely randomized design as pot culture with the six organic sources (s1 to s6 used in field experiment) as treatments (T1 to T6) together with three controls, and were replicated thrice. The recommended dose of NPK for colocasia @ 80: 25: 100 kg ha-1 was applied through organic sources on N equivalent basis as per the treatments. Application of FYM + wood ash +PGPR mix I (s2) took less number of days (24.33 days) for 50 per cent sprouting of seed corm during first year. Application of poultry manure along with wood ash, PGPR mix I and vermiwash (s6) and in situ green manuring with daincha (g2) found superior with respect to growth characters such as plant height, number of leaves per plant, leaf area and leaf area index (LAI). The interaction s6g2 recorded taller plants, higher leaf area and LAI during both the years. Taller plants were produced by s6g2 at 4 MAP and s6g1 at harvest compared to C1 (151.48 cm) during first year. Organic treatments performed better than C2 and C3 with respect to all growth parameters. FYM + wood ash and poultry manure + wood ash recorded the highest number of cormels per plant during first and second year respectively. Mean weight of cormel was higher in s6 (34.86 g) during first year and in s3 (26.01 g) during second year. The application of poultry manure along with wood ash, PGPR mix I and vermiwash (s6) recorded the highest cormel yield (18.68 t ha-1 ) and corm yield (12.21 t ha-1 ) under pooled analysis. Organic treatment s5 recorded the highest cormel to corm ratio (1.80) during second year. In situ green manuring with daincha (g2) recorded the highest mean cormel weight during both the years while cormel and corm yield in pooled analysis were also the highest with this treatment. The treatment s3g2 recorded the highest mean weight of cormel and the treatment s6g2 recorded the highest cormel yield under pooled analysis (19.02 t ha-1 ). The treatment s5g1 registered the highest cormel to corm ratio during second year. The organic treatments s3g2, s5g1, s5g2, s6g1 and s6g2 were found to be equally effective as C1 in case of corm and cormel yield of taro. The treatment s6g2 recorded a 0.90 percentage increase of cormel yield over chemical nutrient management during first year and a 2.67 percentage increase of corm yield over chemical nutrient management for pooled mean. The treatment combinations s3g2, s5g1, s5g2, s6g1 and s6g2 were found superior to C2 in case of corm yield, cormel yield and mean cormel weight. The treatment s6g2 recorded a 37.83 percentage and 27.82 percentage increase of cormel yield and corm yield respectively over KAU organic POP for pooled mean. The treatments s3g2, s4g2, s6g1 and s6g2 during first year and s3g2, s5g2 and s6g2 during second year recorded significantly higher mean weight of cormel than C3. All the treatment combinations in case of corm yield and all the treatment combinations except s1g1 in case of cormel yield recorded significantly higher value than C3. During second year, the treatments s5g1 and s2g2 recorded the highest harvest index (0.60) and were significantly superior to C2 (0.47). The organic source s6 and in situ green manuring g2 recorded the highest dry matter production (DMP). Treatment combination s6g2 (8.37 t ha-1 ) during first year and s3g2 (6.55 t ha-1 ) during second year recorded the highest DMP. Except s1g1, s1g2 and s4g2, all other treatment combinations resulted in significantly higher DMP compared to C2. All organic treatments were significantly superior to C3 with respect to DMP during both the years. The organic source s6 and in situ green manuring g2 were found superior in improving quality characters of cormel. The higher N and K content and uptake were noticed in organic source s6, while P uptake was higher in s3. In situ green manuring g2 resulted in higher NPK contents and uptake. The highest N (149.03 kg ha-1 ) and K (232.80 kg ha-1 ) uptakes were recorded with treatment combination s6g2 during second year. During first year, the treatment s3g2 recorded the highest tuber P content and P uptake (35.12 kg ha-1 ). The treatment combination s6g2 was significantly superior to C1 in case of K uptake during first year. The treatment combinations s2g1, s2g2, s3g1, s3g2, s5g1, s5g2, s6g1 and s6g2 were found superior to C2 in nutrient content and uptake. The organic treatments were superior to absolute control in nutrient contents and uptake. The organic source s5 recorded the lowest EC during second year. The organic sources s5 and s6 resulted in higher organic carbon and available N content in soil while available P content of soil was the highest with s3. In situ green manuring with daincha found superior in organic carbon, available N and available P content of soil. Available N content in soil was the highest in s6g2 during first year. The treatments s2g2 and s3g2 were found to be significantly superior to C1 and C2 during second year with respect to available P status. The organic treatments were found superior to C3 in case of pH, organic carbon and available NPK. The organic sources s5, s3, s6 and in situ green manuring g2 resulted in higher total organic carbon and recalcitrant carbon, labile carbon and water soluble carbon content of soil. All organic nutrition treatments were found superior to control treatments in soil organic carbon buildup. Balance sheet of K was positive for s3g1, s5g1, s6g1, s6g2 and C1 after first year of experiment and the N balance was positive for absolute control after second year. The organic source s6 and in situ green manuring g2 registered the highest net income and BCR. Treatment combination s6g2 resulted in the highest net income (₹737241 ha-1 ) and BCR (2.82). All the treatments except s1g1 and s2g1 recorded higher net income and the treatments s4g1, s5g1, s6g1 and s6g2 resulted in higher BCR than C1. The treatment s6g2 recorded a 43.96 percentage and 6.02 percentage increase of net income and BCR respectively over chemical nutrient management for mean. All treatment combinations except s1g1 and s2g1 recorded higher net income and all except s1g1, s2g1 and s3g1 recorded higher BCR compared to C2. The treatment s6g2 recorded a 54.71 percentage and 19.49 percentage increase of net income and BCR respectively over KAU organic POP for mean. All organic nutrition treatments recorded higher net income and all treatments except s2g1 and s3g1 recorded higher BCR compared to absolute control. In pot culture study, the treatments T6 and T5 in case of pH, absolute control in case of EC, T2 and T3 in case of organic carbon and available P and T6 and C1 in case of available N and K were found superior throughout the growing period. The higher microbial population was observed with organic sources T6, T5, T3 and T2. The organic sources T5 and T3 recorded the highest dehydrogenase activity. The treatments T6, T3 and T5 excelled in rooting pattern and root anatomical characters. Significant and positive correlation was observed between nutrient uptake and root apex diameter, late metaxylem number, early metaxylem number and stele diameter. Corm initiation was early (between 1 MAP and 2 MAP) in treatments C1 and T6 while it was between 2 MAP and 3 MAP in all other treatments. Control C1 and T6 recorded the highest corm and cormel weight per plant during initial stages and later stages respectively. The highest values of cormel bulking rate were observed between 3 MAP and 4 MAP. The treatment T6 recorded the highest bulking rate during 3-4 MAP, T3 and T5 during 4-5 MAP and T2 during 5-6 MAP. The study revealed that application of poultry manure, wood ash, PGPR mix I and vermiwash, along with in situ green manuring of daincha in taro resulted in higher growth, yield, quality, net returns and BCR under organic nutrition and hence can be recommended for its organic nutrient management. All the organic nutrient management practices were found to improve soil organic carbon build up. Application of poultry manure, wood ash, PGPR mix I and vermiwash as organic sources was also found to promote the rooting and tuberisation in taro.ThesisItem Open Access Approaches to assess chlorpyrifos degradation in northern laterite soils of Kasaragod (AEU 11)(Department of Agronomy, College of Agriculture , Vellanikkara, 2022) Shakkira, KK; KAU; Sindhu, P VWeeds have been a persistent menace for farmers since the advent of agriculture. Among several methods adopted for controlling weeds, chemical control is the widely used and most effective. However, the extensive use of herbicides has led to the generation of a wide range of problems including development of herbicide resistant weeds. As a result, extensive research is being done to exploit non chemical methods of weed management. The mechanism of allelopathy has been suggested as a potential biorational method towards this goal. Hence the present study entitled “Allelopathy for weed management in field crops” was conducted during February-October 2021 in the Department of Agronomy, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur. The study consisted of two parts viz., screening Andrographis paniculata, Plectranthus ambonicus and Tagetes minuta for their allelopathic potential, and evaluating alleloapathic effect of these plant extracts on weeds and the test crops rice, cowpea and green gram. Cold water, hot water and methanol extracts of these plants were prepared at six concentrations viz., 5 %, 10 %, 15 %, 20 %, 25 % and 30 % in a completely randomized design (CRD) in factorial arrangement with three replications. In the first experiment plants were screened for their allelopathic potential against upland weeds in 165 plastic trays (25 cm x 20 cm x 5 cm) that were filled to three-quarters with uniform quantity of soil (1.5 kg) collected from an open area. Best 10 treatment combinations from this experiment and a control with distilled water were carried over to the second experiment. The second experiment consisted of two parts; in petri plates to test the phytotoxic activity on test crops (cowpea, green gram and rice) and in pot culture study with test crops and weeds. Both studies were carried out in completely randomized design (CRD) in factorial arrangement with two factors and three replications. Factor A consisted of time of application (on the day of sowing and 6th day after sowing). Factor B consisted of the best 10 allelopathic treatments from experiment 1. Experiment on screening allelopathic plants for their potential to control upland weeds revealed the significant influence of the plants, the method of extraction and the concentration of extract on weed growth parameters such as weed density and weed dry weight. Broad leaved weeds were more sensitive to allelopathic extracts than grass weeds. Reduction in weed germination count and dry weight after one month of application was noticed with methanol extract of Tagetes minuta at 30 per cent concentration and was 6.67 nos./m2 and 21. 33 g/m2 respectively as compared to control (68.33 nos./m2 and 54. 25 g/m2 ). Pre mergence application of Andrographis paniculata methanol extract at 30 per cent concentration was the next best treatment. Allelopathic effect of plants was significant only for a short period of time i.e. up to one week after application, indicating absence of residual action. Germination indices and seedling growth parameters of test crops were adversely affected by the application of allelopathic extracts. Among test crops, cowpea and green gram were more sensitive to allelopathic extracts than rice. A notable delay in germination of test crops, in shoot and root length, and in fresh and dry weights were observed by the application of allelopathic treatments. Phytotoxicity symptoms were observed on test crops both under laboratory condition and in pot culture. Root decay and reduction in number of rootlets were observed by the pre emergence application of 30 and 25 per cent methanol extract of Tagetes minuta. When Tagetes minuta methanol extract was applied at 30 or 25 per cent as pre mergence treatment, germination of cowpea and green gram started on the 4th and 5th day after sowing as compared to the 2nd day in control. Root length reduction was more pronounced than shoot length reduction. The reduction was 43.29 and 41.46 per cent in cowpea, and 41.56 and 37.05 per cent in green gram, due to pre emergence application of 30 and 25 per cent methanol extract of Tagetes minuta in petri plates. In pot culture study, root reduction of 70.85 and 71.01 per cent in cowpea and green gram by the pre emergence application of 30 per cent methanol extract of Tagetes minuta as was observed. A notable delay in weed germination and weed dry weight reduction were observed by 30 and 25 per cent Tagetes minuta methanol extract applied as pre emergence treatment and their residual inhibitory effect in the soil persisted up to one week. Based on the results of the study, pre emergence application (on the day of sowing) of methanol and cold water extracts of Tagetes minuta and Andrographis paniculata at 30 per cent concentration can be recommended for control of broad leaved weeds in uplands.
