Introduction Weeds are unwanted plants growing in crops and competing with them for nutrients, water, space, light, etc. Weeds serve as alternate host for several pests and diseases. Wider spacing, frequent irrigation and liberal use of manures and fertilizers create favourable conditions for prolific weed growth which can cause serious damage to potato crop. Early weed competition affects the crop yield significantly. Weed management is the process of limiting the weed infestation so that nursery could be grown profitably.

Weeds found in TPS Nursery Scientific NameCommon NameScientific NameCommon Name Amaranthus viridisPig weedCyperus rotundusNut sedge Anagallis arvensisPimpernelMelilotus albaSweet clover Avena fatuaWild oatMelilotus indicaSweet clover Chenopodium albumPig weedPhalaris minorCanary grass Convolvulus arvensisBind weedPoa annuaBlue grass Cyperus iriaFlat sedgeSetaria glaucaCarpet weed

Weed management in TPS Nursery Weed management is a difficult task and application of various systems together is necessary for effective control of weeds. Following are the weed management systems: Cultural Method Physical and Mechanical Method Chemical Methods

Creating unfavorable environment for weeds growth to discourage its growth in TPS Nursery. Smother Crop Varieties: Vigorous varieties like Kufri Badshah and Kufri Jyoti are better competitors of weeds. Incorporating green manure crops can reduce weed infestation. Hot Weather Cultivation: Some perennial weeds such as Cynodon doctylon, Cyperus rotundus are reduced by deep ploughing during summer months (May–June). Good Seed Bed Preparation: It gives the good start to the crop by ensuring quick emergence of potato. Mulching at appropriate time can also reduce weed incidences in the nursery. Cultural Method:

Proper Planting Method: Planting of well sprouted tubers at sufficient soil moisture, proper depth, time and maintaining high plant densities per unit area helps reducing nursery weeds. Application of Light Irrigation: Application of light irrigation at short interval helps early tuber sprouting which can compete better with weeds in the nursery. Placement of Manures and Fertilizers: Application of manures and fertilizers in bands near root zone of seedlings reduces nutrient loss. It also deprives the weeds of nutrients thus controlling their growth. Cultural Method:

Cultural Methods: Mulching: Mulching reduces the growth of weeds in nursery. It prevents the supply of light to the weeds thus inhibiting their growth. It also provides an effective physical barrier to weed emergence. In addition it helps to conserve moisture and maintain temperatures conducive for germination of True Potato Seeds. Dry straw, grasses, paper, plastic and polythene films can be used for mulching. Mulch should be thick enough to prevent light penetration to suppress photosynthesis in weeds.

Physical Methods Physical methods are also called manual and mechanical methods of weeds control. They do not involve chemicals but require manual, mechanical or animal energy for eradicating weeds. Manual weeding is the mechanical method of weed control used in a TPS nursery. Manual Weeding: Pulling out weeds by hand, hand hoe, spade etc is a common practice for weed control in TPS nursery. This method is also useful for destruction of weeds growing between plants where they can not be controlled by any other means. Potato seedlings need weed protection only until four weeks after crop emergence.

Chemical Weed Control Controlling weeds using chemicals can be very effective and fast method of controlling weeds. Use of chemicals avoids mechanical damage to nursery seedlings which may occur in manual or mechanical weeding. Chemical weed control is quick and less laborious. Contact of herbicide may be detrimental to the seedlings and therefore using pre-sowing herbicides must be preferred. Intercultural operations in nursery can be minimized by this method.

Commonly used Herbicides Basalin (Fluchloralin): Basalin is chemically, N–(2-Chloroethyl)–2,6- dinitro–N-Propyl–4–(Trifluoromethyl) aniline and belongs to dinitro- aniline group. It is volatile and available as emulsifiable concentrate or granules. It is a pre-emergence weedicide susceptible to photo- degradation. It is absorbed by root and translocated in the plant. Pendimethalin (Stomp): It is chemically, N-(1–Ethyl Propyl)–2, 6 dinitro–3, 4- xylidine, belonging to dinitro–aniline group and available as emulsifiable concentrates or granules. In potato, it is used as pre- emergence weedicide. Pendimethalin is effective for broad leaved weeds. It has long lasting phyto-toxicity effects.

Commonly used Herbicides Linuron (Afalon): It is chemically, N’–(3,4–dichorophenyl)–N- methoxy–N–Methylurea. Linuron is a substituted urea compound and selective pre–emergence herbicide for medium to heavy soils under medium rainfall conditions. In potato, it controls both broad leaf and grassy weeds. Atrazine: It is 2-Chloro–4 ethylamino–6 isopropylamino–1,3,5 triazine compound. It absorbed through roots and translocated to other plant parts. It is best suited in areas of low rainfall areas. It effectively controls both Monocot and Dicot weeds and has no residual effect on succeeding crops.