Growers can visualize the difference in plant growth with respect to vegetative and reproductive parameters when they grow under net and open field situation. Can anyone please explain few important parameters which are going to vary under these situations and why?.
In the open field, one can assume that crops will be subjected to maximal pest pressure, maximal light intensity, and access to pollinators. Once under a protective net, there is firstly a shading effect that is not usually considered, and this may or may not affect the crop's growth (depending on whether a light reduction is beneficial, detrimental, or neutral). Depending on the size of the holes in the screen, certain insects will be excluded; if the holes are too large, you may be allowing certain pests in and excluding their larger competition and predators. Nets can also exclude beneficial pollinators, so it may necessitate the application of pollinators inside the netting.
If the ‘artificial net’ reduces light intensity (especially, photosynthetically active radiation), that may lead to changes such as (a) increase in specific leaf area (m2/g leaf dry weight) as plants trying to maximize the capture of light under low light intensity, (b) increase in shoot:root ratio: another mechanism of adaptation in plants growing under low light intensity.
My observations on net house studies are that the light intensity may be low (depending on transparency of the roofing material) all potted plants may not get uniform light ( resulting in etiolated plant growth) ,as has been highlighted problem of pests , including rat and squirrel,temperature in net house may be slightly high, spacing may not be same as in field and ultimately plant growth may not be similar to field and even plant tries to complete life cycle earlier than in field .
Very good question Dr Kalaivanan. In perennials , we have seen that open field conditions suit more than net house conditions , but same may not be true for annuals. Perennial crops have much higher photosynthetic requirements than annuals . Another interesting aspect of this question is, when we need to have vegetative flushes , we do keep even perennial crops like citrus under net house conditions for multiple flushing , to be later used in large scale budding .
Some very good answers have been presented by researchers enlightening major differences between open fields and net houses. Anoop Kumar spoke about differences of perennials. All the points are OK. I will elaborate only one point which has not discussed. Plants can exhaust more volume of soil in the open field compared net house and can undertake more nutrients. Therefore, they can flourish well. That cause the major difference in growth.
In addition to the reduction in light intensity (photosynthetically active radiation), which I think is the most important, other changes occur in the microclimate of the network. For example, the reduction in temperature, increased humidity and a reduction in wind speed, for some crops can be very important.
Dear All,
one aspect is still missing and this is the colour of the nets.
There is an appreciable literature on influences of black, white and green netting and even other colours (blue and grey) have been tried out. Just google "coloured net shades".
Cheers, Kees
Yes, color of the net may affect light penetration but it is usually kept as green.
Even though I agree with all answers I focus on difference in PAR reaching the plant canopy even light distribution in the canopy,
Some plants need high PAR, like C4 plants,
C3 plants also requires other PAR level
some plants need very diffused light for photosynthesis,
What every should focus is shade net is made with very different levels of shading, as high as 90% shading, 20% shading, of can be made at desired levels of shading, thus one adjust the shade leves with the plant spp requirements.
Thanks
If we are concentrating on light factor then we have to consider shining intensity and total shining hours/day. It means that PAR will be more important in Western countries than Asian and African countries that are located around the Equator.
I feel that we are now widening the subject to glass houses but that makes little sense.
The question was on the influence of netting and that is a very different issue.
Cheers, Kees
The queries were
Thank you all for giving valuable and very elaborate answer to my question.
Thank you all for giving valuable and very elaborate answer to my question.
Yes, I also think that this question has been dealt in a very good manner with excellent answers,
This question is very broad, but generally it is the climate conditions that make the deference especially the temperature and humidity, the plant enjoys better controlled conditions than on the field.
in case of lillium i have observed using the shade net will extent the growing period also it will protect from sun scorching thus results in better bulb weight with against the better leaf area and leaf area index
I have an interest in soil science, the chemistry and biology, as well as geology of the soil, and it seems to me that the shade would affect the water evaporation and soil respiration rates, which would affect the microbiota - and this would perhaps influence the productivity or growth of the plants as well.
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