PhD

The present investigation entitled “Weed management in ginger (Zingiber officinale Rosc.) was carried out at the Agronomy Farm, College of Horticulture, Vellanikkara during March 2013 to January 2015 using the variety Karthika. The main objective of the investigation was to study the weed flora of ginger in the major ginger growing districts of Kerala and to find out efficient, economic and eco-friendly weed management practices in ginger. The investigation was carried out in two parts. 1) Survey of weed flora of ginger in the major ginger growing districts of Kerala 2) field experiment on management of weeds in ginger.
Stratified survey was done in major ginger growing districts of Kerala namely Waynad, Palakkad, Idikki and Thrissur districts during 2013 and 2014. The average number of dicots, monocots and sedges found growing in ginger plots in these districts were in the order of 69.1, 22.0 and 8.8 per cent respectively. Based on the SDR values, the most dominant broad leaved weed species observed in the Palakkad district were Scoparia dulcis, Ageratum conyzoides, Mollugo pentaphylla and Ludwigia parviflora. Leptochloa chinensis was the most dominant grass weed. Fimbristylis miliacea and Cyperus iria were the dominant sedge species. In the Thrissur district Cyperus difformis was the most dominant sedge. Among broad leaved weeds, Alternanthera bettzickiana had the highest SDR value. Among the grasses, Brachiaria mutica, Eragrostis japonica and Setaria sphacelata dominated in Thrissur district. In the Wayanad district Spilanthes radicans and Ageratum conyzoides emerged as the most dominant broad leaved weed species. The most dominant grass weed was Digitaria ciliaris. Among the sedges, Cyperus iria was the dominant species. In Idukki district Ageratum conyzoides and Spilanthes radicans were the most dominating broad leaved weed species. Among grasses, Eragrostis sp. recorded the maximum population followed by Ischaemum indicum.
The field experiments were laid out in RBD with three replications during 2013-2015. The treatments included were pendimethalin @ 1.5 kg /ha after planting but before mulching, oxyfluorfen @ 0.20 kg /ha after planting but before mulching, metribuzin @ 0.525 kg /ha after planting but before mulching, glyphosate @ 0.80 kg /ha just before the emergence of sprouts of ginger, glufosinate ammonium @ 0.45 kg /ha just before the emergence of sprouts of ginger, pendimethalin @ 1.5 kg/ha + one hand weeding at first mulching, oxyfluorfen @ 0.20 kg/ha + one hand weeding at first mulching, metribuzin @0.525 kg/ha + one hand weeding at first mulching, soil solarization for 45 days before planting ginger, POP recommendations (KAU) and unweeded control
In the second crop season (March 2014 to January 2015) two additional treatments namely, combinations of glyphosate with pendimethalin (T12) or oxyfluorfen (T13) were additionally included. The combinations of these herbicides were applied at twenty five days after planting, just before the emergence of sprouts of ginger.
Major weeds found in experimental field in both the years were broad leaved weeds comprising of Ageratum conyzoides, Alternanthera bettzickiana, Borreria hispida, etc. Pennisetum pedicellatum and Brachiaria sp. were the dominant grass species. Cyperus iria was the only sedge. Significantly the lower weed population, weed dry weight and nutrient removal by weeds were observed in PoP (T10) followed by pre emergence herbicides + hand weeding (T6, T7 and T8), at 45, 90 and 180 DAP. Among the additional treatments, oxyflourfen+glyphosate (T13) registered the lowest dry matter production, weed population and nutrient removal by weeds at 45, 90 and 180 DAP and was on par with POP.
The plant growth parameters like number of tillers per plant, number of leaves per tiller and plant height were maximum in POP (T10) followed by pendimethalin + hand weeding and Oxyfluorfen + hand weeding which were significantly superior to all other treatments. The additional treatment tried in 2014-2015, glyphosate + oxyfluorfen (T13) also produced higher tiller count, number of leaves per tiller and height of plant. The treatment T13 was at par with T10 and significantly superior to all other treatments.
The highest fresh yield and dry yield were recorded in POP (T10) followed by oxyflorfen + hand weeding (T7). The third best treatment was pendimethalin + hand weeding (T6) followed by soil solarisation (T9). The newly added treatment glyphosate + oxyfluorfen (T13) also gave the highest fresh (13.53t/ha) and dry yield (4.59 t/ha) which was on par with POP. Pendimethalin, metribuzin, glyphosate and glufosinate ammonium were far inferior to produce a reasonable yield of rhizomes. The highest net return was recorded by POP recommendation (T10) followed by oxyflorfen + hand weeding (T7). The highest B:C ratio was recorded by oxyfluorfen + hand weeding (4.7) followed by pendimethalin + hand weeding (4.4) and PoP (3.95). When laborers are available in plenty, PoP practice of weed removal by hand at 45 and 90 DAP is the best as this is environment friendly. If labour shortage is experienced oxyflorfen + hand weeding or pendimethalin + hand weeding can be adopted. The additional treatment glyphosate + oxyfluorfen (T13) tried during 2014-2015 only was also effective in controlling weeds and giving a good yield. But the treatment needs further verification by field trials.
The total fungal and bacterial count two months after spraying of herbicides also showed the maximum count in the treatment PoP (T10) which was on par with unweeded control (T11). Herbicide residue analysis in ginger showed that all the promising herbicides to control weeds in ginger recorded below detectable level of residue in rhizomes.