What irrigation methods can be used in a walnut orchard?
Walnut orchards can use conventional irrigation, and water-saving irrigation is encouraged. The commonly used irrigation methods include: border irrigation, basin irrigation, furrow irrigation, hole irrigation, sprinkler irrigation, subsurface irrigation and drip irrigation, among which sprinkler irrigation, subsurface irrigation and drip irrigation are relatively advanced water-saving irrigation methods.
1. Border irrigation Border irrigation, also called zoned irrigation, is a method in which the entire tree rows of a walnut orchard are made into multiple large borders and water is diverted for irrigation. It requires flat terrain and sufficient water supply. This method has the advantages of a large wetting range, a large irrigation volume and simple operation; its disadvantages are a large water consumption and easy soil compaction, and timely hoeing and loosening of the soil are needed after irrigation.
2. Basin irrigation Basin irrigation is irrigation by diverting water into the tree basin. Before irrigation, the soil in the basin can first be loosened so that water penetrates easily; after irrigation, the surface soil is raked loose, or covered with grass, to reduce water evaporation. The advantages of this method are a small irrigation volume, water saving and little damage to soil structure. However, the range of soil wetted is relatively small, and it still has the disadvantages of causing soil compaction and damaging soil structure.
3. Furrow irrigation Furrow irrigation is a method of irrigation by opening furrows between walnut tree rows and diverting water into them. It has the advantages of a small irrigation volume, economical water use, reduced ineffective soil evaporation, high water use efficiency, and no soil compaction because soil is backfilled after irrigation, and it also facilitates mechanized cultivation, but the wetted area is relatively small.
4. Hole irrigation Hole irrigation is digging holes at the outer edge of the tree canopy projection and pouring water into the holes until they are full. The number of holes depends on the size of the tree canopy, generally 8~12, with a diameter of about 30 cm; the depth of the holes should be such that thick roots are not damaged, and the soil is returned after irrigation. For hole irrigation during drought periods, the holes can be kept for a long time without covering with soil. This method uses water economically, wets the root soil over a relatively wide and uniform range, and does not cause soil compaction, so it is suitable for promotion and use in areas lacking water sources.
5. Sprinkler irrigation Sprinkler irrigation is a semi-automated irrigation method composed of a water source, a power pump, water conveyance pipes and sprinkler heads. Compared with traditional irrigation, it can save 10%~30% of water, and it can keep the soil in its original loose state and reduce damage to soil structure. Sprinkler irrigation can be carried out together with foliar fertilizer spraying, and has the advantages of regulating the orchard microclimate and improving nut quality.
6. Subsurface irrigation Subsurface irrigation plus straw mulching is one of the effective technical measures for water saving and moisture conservation in dry orchards, and has the characteristics of saving labor, saving water, low cost, high benefit, ease of use, no evaporation loss and no soil compaction. A subsurface irrigation system consists of 3 parts: an infiltration tank, infiltration pipes and a valve. The capacity of the infiltration tank is above 10 cubic m; the infiltration pipes are plastic pipes as long as the tree rows and 2 cm in diameter, with 3 needle-sized small holes punched on both sides and the top of the pipe at intervals of about 40 cm; the main pipe is installed on a valve about 10 cm above the bottom of the tank, and a filter screen is installed on the infiltration pipe to prevent pipe blockage. In an orchard with a row spacing of 3 m, 1 infiltration pipe should be buried per row, and where the row spacing is 4 m or more, two infiltration pipes should be buried. Water continuously seeps through the small holes in the plastic pipes into the soil within the root zone.
7. Drip irrigation The water source forms water droplets or a fine stream through a drip irrigation device, slowly seeping into the root soil layer. This method saves about 50% of water compared with sprinkler irrigation, is about 1/4~2/5 of ordinary irrigation volume, can maintain stable soil moisture, and at the same time can maintain the aeration of the root-zone soil, save labor, is not restricted by orchard terrain, and significantly increases yield.
Walnut orchards with the conditions can use water-saving irrigation methods such as sprinkler irrigation, full irrigation or subsurface irrigation as much as possible. Drip irrigation, subsurface irrigation and the like can also implement integrated water and fertilizer, carried out together with topdressing, saving time and labor with good results.