ABSTRACT
Papaya orchards should be free from unwanted plants or weeds for better growth and development. Weeds must be controlled, especially during the initial stages of orchard establishment. Use of herbicide, hand weeding, mulching and deep hoeing, either singly or in combination is recommended during the first year to check weed growth. Weeding should be done on regular basis, especially around the plants. Applications of Fluchloralin or Alachlor or Butachlor (2.0 g/ha) 2 months after transplanting can effectively control the weeds for a period of 4 months. Mixture of oryzalin + oxyfluorfen is a broad spectrum herbicide which is used in papaya fields for weed management, but the use of oryzalin is safe around young plants but should not be applied to green stems. Oxyfluorfen is also effective as a preemergence with sufficient irrigation, but sometimes causes vapour drift to recently emerged leaves. Use of cover crops can also be a practical method to control weeds. Mechanical cultivation between rows is appropriate to disturb the shallow roots. The organic material such as crop residues, farm yard manure, by-product of the timber industry may be used with 5-15 cm layer and keep mulch 30 cm away from the trunk. Inorganic materials such as plastic films of different colours and thicknesses are used efficiently. Mulching in papaya helps by reducing soil compaction, soil erosion, leaching of fertilisers, winter injury, weed problems, retain soil moisture and improve the quality of produce. Papaya plants are dependent on mycorrhizas for their nutrition and benefit from soil mulching and appropriate drainage that facilitate biotic interactions in the rhizosphere and water and nutrient uptake, especially phosphorus and nitrogen (Jimenez et al. 2014). Four genera and 11 species of arbuscular mycorrhizal fungi have been reported associated with papaya roots: Glomus, Acaulospora and Gigaspora, among others (Khade et al. 2010). Mycorrhizal interactions of male and female papaya plants may differ: females seem more responsive to changes in soil fertility and readily adjust mycorrhizal colonisation accordingly (Vega-Frutis and Guevara 2009). Among different mulching material and methods, namely organic mulch, plastic mulch, bare soil with mounding and flat ground methods, the best treatment combination was plastic mulch with mounding, which significantly differs from the remaining for management of phytophthora (root rot) disease.
