192 Papaya
17.2.1 Nutrient Management
Fertiliser application may be required depending on the location of the orchard and
the variety (da Silva et al. 2007). Use of balanced applications of macro- and micro-
nutrients helps in better crop production. Papaya plants are dependent on mycorrhiza
for their nutrition and benefit greatly 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). The nutrient requirements
of papaya plants are high. Mineral nutrients are taken up by plants grown at full
sunlight as macronutrients, namely K > N > Ca > P > S > Mg and micronutrients
like, Cl > Fe > Mn > Zn > B > Cu > Mo. Nitrogen, phosphorus, and potassium, very
important nutrients for metabolism and extracted in high amounts. A ton of fresh har-
vested fruits contains 1770, 200, and 2120 g of each of these nutrients, respectively
(Jimenez et al. 2014). However, under polyhouse cultivation minimum use of nitrog-
enous fertiliser is recommended to avoid fast growth of plants (Morales-Payan and
Stall 2005). Soil application of paclobutrazol, a growth retardant, at 1000 mg/L
resulted in reduced overall height and reduced height at which first flowers bud; it
did not affect the start of production or yield (Rodriguez and Galan 1995).
17.3 Components
Protected cultivation technology has two major components. One is the infrastructure
involving frames, cladding materials, irrigation system, tools, implements and other
engineering inputs. These inputs ensure optimal light, air temperature, water and
plant growth requirements. This optimal aspect of climatic parameters involves
simple to most advanced engineering inputs such as automation, etc. to regulate sev-
eral parameters such as ventilation which is one of the most important components
in a successful greenhouse production. In the absence of proper ventilation, green-
houses and their plants can become prone to problems like high temperatures,
development of pathogens etc. Air circulation in protected structures is a must
which is done by providing ventilation devices. Importance of cladding materials
in protected cultivation can hardly be overemphasised. Their quality and cost are
important besides certification. Micro irrigation and fertigation involve, a lot of sci-
ence and technology, demanding research for continuous improvement. This aspect
of the protected structure provides optimal conditions to plants to grow normally.
The advance engineering tools are assisting various operations in more precised way
and ultimately contributing to harvest the quantity and quality fruits. Polyhouse and
net houses are used for cultivation of this crop as given below.
17.3.1 Polyhouse..................................................................
Ideal features of polyethylene have increased the use of polyhouses in place of glass-
house throughout the globe. It has not only reduced the initial cost but also increased
the popularity of greenhouse by simplifying the installation technology. Generally,
two types of polyhouses are used in hilly and in plain regions where simple bamboo
or GI-pipe-based polyhouses are used (Singh et al. 2000).