While growing this type of WM we are facing two problems Seedless are triploids with wery hard surface of seed. As from it germination is very low so special effort are needed to brake it in aim that sprouting starts.For succesfull germination we must obtain temperature of 29-30o C and air humidity has to be very high ,also. After seedling start sprouting we go to normal regime. Some respected autorities recomend scarification of seed edges hard layer. By all means if those two recomendations mentioned above are ingnored we are facing disaster in young plant production of seedless WM.
Second problem is during fruit setting. In order to have any pollination and setting we need regular watermelon as seedless are strile and do not produce pollen. We plant one plant of ''normal'' WM after every four of seedless.Research showed that insect are flying in the straight line so this system proves to be the best.
Region of Negotin
Watermelon as a crop is known to be grown and cultivated since the beginning of nineteen century in villages Bukovce, Kobisnica, Prahovo and Radujevac. So called Vlaska Valley located on the slopes of Negotin with favorable altitude of 35-50 meters have lot of sunny days during season of growing are good starting point for WM growing.
Tradition on growing WM stands still to the present times. For decades growers were cultivating their own varieties by choosing seed from the best plants to be sown for next crop. One of the best known local varieties was '' Negotinka '' with fruit 6-12 kg in weight. Fruit of this variety is pure green and flesh red and very tasty. Seed inside was big and black coloured. Yield was very good so region became known for its production capabilities. Many old written documents on WM growing in Negotin area from that period still exist.
In seventies and eighties village of Recka made serious start in WM growing. There are some innovative production techniques developed in Recka. Apart from WM grafting so regular and successful among Recka growers some of them organized and conducted production in most southern part of former Yugoslavia - Republic of Macedonia and on top of that export to Croatia and Slovenia have been organized. Today it would be considered as international business venture!
Today circumstances have changed. Market is much smaller but still there are few good growers keeping the tradition and yet following all modern production trends. That enables them to have yield of 90 tons per hectare and produce large fruited WM. As curiosity the heaviest fruit in recent competition among Recka growers had 58.4 kg in weight!
Production technology - The way I do it
Success in WM growing on mulch plastic depends on:
Regarding selection and preparation of the plot for WM growing it should be emphasized that in order to achieve big yield we have to pick parcel of high quality soil. In that order Vlaska Valley is a perfect choice a long time ago this valley was a swampland. This results in high content of organic matter (humus, peat) being favorable for WM growth. Lot of sunny day's low altitude and mild winds during night are important growth conditions as well.
One of important pre conditions for choosing the right place is water availability. Modern WM production requires sufficient amount of fresh water during critical grow states. There is artificial water canal passing by so right temperature of water have been achieved, too.
Careful planning is required so those short tunnels would have right orientation toward sun movement. Choosing the right substrate for young plant growing is also required and analyses of macro and microelements of soil is required. Crop rotation have to be considered also as any crop from the family of cucurbits (cucumber, pumpkin, squash, melon) have to be omitted for 4-5 consecutive years. Best culture to be grown before WM are leguminous crops and even if there are some grasses on the plot with deep ploughing they can serve as natural fertilizers. Also take care of herbicide residues.
Watermelons require rather high temperature sum (1.800 hours of sun light) and are very sensitive to temperature oscillation. No frost period have to last at least 180 days. We could have this in Negotin region. In order to secure and have earlier production mulch foliage is put on the ground and on top of it short plastic tunnel are put above young plants. Also drip irrigation system have been put under the mulch cover.
In recent years there have been changes in climate due to the global warming so the right heating and ventilation especially during young plant raise and further raise of transplants under cover is also important.
New highly productive hybrids require a lot of water as they produce strong vegetative plants able to produce and feed a lot of large fruits. Also evaporation factor of WM is rather high (600). In the flowering development stage higher air humidity is important for fruit setting (app. 80%). Highest demand for water is during intensive growth of fruits and after harvests.
For sucessful production it is very important to have healthy and well ''hardened'' young plants.Serious attention has to be focused towards tunnel construction where we will do young plant production. Construction of tunnels and north-south projection of them is important. Good ventilation, fogging, Microsprinklers, heaters and shading equipment have to be inside modern nursery. Most important is to provide sufficient temperature. Good quality plastic has to be a choice, also
Before we start production we have to disinfect all surfaces in nursery. No weeds have to be around the production facilities.
Most of products we do are from grafted plants that sterile environment is required. Rootstock used is from special type of squash (Lagenaria vulgaris) which proved to be the best for the purpose of having higher yield. Root system of grafted plant is much stronger so penetrates deeper into the soil and production is much safer that way. Cold and disease tolerances (Fusarium) are also significantly better. Making of interspecies plant where squash provide water and minerals to WM stem and leafs have positive effect as we got perfect WM fruit with no change in taste. In few recent years we were experimenting with grafting method withoud removing side shouts. In practice it proved to be the best way.Rootstock is more ''in line'' of growth with scion. Callus (joint) is much stronger and healthier (e.g. to Alternaria attack). Second point is that plant is much stronger as it's not waisting energy on shouts and instead concentartes on root system.
Very deep ploughing is required. Ass deep as 40 cm is usual when we intend to grow WM there. During August and September we ''open'' soil with a plough. Good air to water capacity is important even dough we will use grafted plant where root system (squash or interspecies hybrid) is much stronger than with regular WM. Recently special ploughing is done by going as deep as 70 cm in the ground to cultivate the land and to break crust and hardened soil down in the ground. After that we go with regular ploughung 30-35 cm. In the spring as early as possible we have to ''close'' the surface with sowing preparation cultivators and flatten it. That way we would prevent drying of soil. Ten days before putting mulch foil we do cultivation once more. Unnecessary passing of machinery through the surface has to be avoided. It is important that soil in the 15 cm of deep has right amount of water and air.
Specially constructed machine puts foil and drip irrigation to the surface in one passing. Also initial amount of hydro soluble fertilizer is inserted. Next step is to put short tunnels on top of mulch foil. Then we put young plant and have optimal and controlled grow condition.
When plants are big enough we remove short tunnels and does cultivation between rows.Through drip irrigation system we do plant feeding with hydro soluble fertilizers from world known companies. It enables us to do quick intervention if some of important elements in deficiency. Raising good young plants is crucial for WM growing success as all stages of growth are pre-programmed during early plant development. If some mistakes have been done during young plant stage it is impossible to straighten them up during further period!
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While growing this type of WM we are facing two problems Seedless are triploids with wery hard surface of seed. As from it germination is very low so special effort are needed to brake it in aim that sprouting starts.For succesfull germination we must obtain temperature of 29-30o C and air humidity has to be very high ,also. After seedling start sprouting we go to normal regime. Some respected autorities recomend scarification of seed edges hard layer. By all means if those two recomendations mentioned above are ingnored we are facing disaster in young plant production of seedless WM.
Also drip irrigation system have been put under the mulch cover.
Good air to water capacity is important even dough we will use grafted plant where root system (squash or interspecies hybrid) is much stronger than with regular WM. Recently special ploughing is done by going as deep as 70 cm in the ground to cultivate the land and to break crust and hardened soil down in the ground. After that we go with regular ploughung 30-35 cm. In the spring as early as possible we have to ''close'' the surface with sowing preparation cultivators and flatten it. That way we would prevent drying of soil. Ten days before putting mulch foil we do cultivation once more. Unnecessary passing of machinery through the surface has to be avoided. It is important that soil in the 15 cm of deep has right amount of water and air.