Detailed Explanation of the Key Technical Points for Grafted Sparse Planting Cultivation of Seedless Watermelon

Technical points: Grafted cultivation technology for seedless watermelon is a cultivation method that uses plants from the same family, such as gourds, bottle gourds, pumpkins, and winter melons, which have resistance to soil-borne diseases, as rootstocks, and uses seedless watermelon seedlings or branches as scions for grafted seedling raising, then transplanting them to the field after they survive. The main grafting methods for seedless watermelon include cleft grafting, approach grafting, and insert grafting:

1. Cleft grafting, also called cut grafting. The specific operation is to first remove the growing point of the rootstock, use a single blade to split downward from one side between the cotyledons, with a depth of about 2/3 of the hypocotyl and a length of about 1.5 cm, then cut one slice on each side of the hypocotyl below the scion cotyledons, with each cut surface about 1.5 cm, insert it into the rootstock slit so that the scion and rootstock fit smoothly, then wrap the wound 4-5 times with cotton thread, placing the thread end on the rootstock leaf so that the thread can be untied with tweezers after survival; special grafting plastic clips can also be used. This method has a relatively high survival rate, and generally a skilled worker can graft about 60 plants per h.

2. Insert grafting, also called top grafting. When the first true leaf of the rootstock just emerges, cut off the growing point, then use a specially made bamboo stick to insert a small hole diagonally from the top of the cotyledons downward, about 1.5 cm deep, then cut the hypocotyl of the previously prepared scion seedling whose cotyledons have not yet unfolded into a wedge shape with two cut surfaces, and immediately insert it into the rootstock hole so that they fit tightly together. This method requires no wrapping, is simple to operate, and has relatively high work efficiency; a skilled worker can graft about 100 plants per h.

3. Approach grafting, also called tongue grafting. First remove the growing point of the rootstock, then on the rootstock hypocotyl at 0.5-1 cm near the cotyledons, use a blade to make a downward cut at a 45-degree angle, with a depth of 1/2-2/3 and a length of about 1 cm, then make an upward 45-degree diagonal cut at the corresponding part of the scion, with the same depth and length as the rootstock, then gently insert the cut of the scion seedling into the cut of the rootstock seedling, then wrap tightly or clamp with cotton thread or special plastic clips, and after the graft union heals, cut off the root of the scion. This method has a high survival rate, but the operation is relatively difficult and work efficiency is not high, so it is used relatively little in production.

Main technical and economic indicators: Using grafted sparse planting cultivation for seedless watermelon can prevent the occurrence of fusarium wilt and solve the problem that watermelon cannot be continuously cropped on the same land; at the same time, because the rootstock has strong fertilizer absorption capacity, it can save 20%-40% of fertilizer use; moreover, using gourds and pumpkins as rootstocks can effectively increase the cold tolerance of watermelon, which is beneficial for protected cultivation of watermelon in early spring, allowing earlier cultivation and earlier marketing; in addition, through grafted sparse planting cultivation, watermelon growth can also be accelerated and watermelon yield greatly increased. Compared with own-rooted seedlings, it can generally increase yield by about 60%.