What crops are suitable for intercropping under prickly ash trees?

Prickly ash, also known as large pepper, Qin pepper, and Sichuan pepper, is a common plant in China. Because it can be used both as a seasoning and as a traditional Chinese medicine, it is widely cultivated. However, since young prickly ash is not easy to plant successfully, farmers adopt intercropping models to enhance soil fertility. So what crops are suitable for planting under prickly ash trees? What crops can be intercropped under the trees?

In young prickly ash orchards or prickly ash orchards with low tree coverage, intercrops can be planted between the rows of prickly ash trees. Planting intercrops in a prickly ash orchard can cover the soil, prevent erosion, reduce weed damage, increase soil humus, and improve soil fertility; at the same time, it allows rational use of the land. Intercropping grain and other cash crops can both increase grain production and raise income, achieving the goals of “supporting the field with the orchard” and “supporting the long term with the short term.” Planting intercrops also has certain disadvantages, as they can easily compete with the prickly ash trees for water, nutrients, sunlight, and other unfavorable effects. However, if the types of intercrops are chosen appropriately and planted properly, the unfavorable effects can be reduced to a minimum.

The main trunk of prickly ash is relatively low, so intercropping is only suitable during the young stage or early fruiting stage. Large trees in full fruiting stage are generally no longer suitable for intercropping. Even during the young stage, attention should be paid to selecting the types of intercrops, following the principle of not affecting the growth and development of prickly ash. Good intercrops should meet the following conditions: a short growth period, taking up relatively few nutrients and little water, with periods of high water and fertilizer demand different from those of prickly ash trees; relatively short plants that will not affect the light conditions of the prickly ash trees; the ability to improve soil fertility, with fewer pests and diseases, and without worsening the pests and diseases of the fruit trees; and relatively high economic value of the intercrops themselves.

Generally, legumes, root and tuber crops, wheat and barley, melons, and vegetables are suitable. Suitable legumes for intercropping include peanut, mung bean, soybean, red bean, and others. These crops are generally relatively short, and their nitrogen fixation can improve soil fertility, with less conflict over fertilizer with prickly ash trees. Among them, peanut is short and needs relatively little fertilizer and water, making it a good intercrop for prickly ash orchards on sandy land.

Root and tuber crops are mainly sweet potato and potato. Sweet potato needs relatively little fertilizer and water in the early stage, so it has little impact on prickly ash trees. In the later stage when tubers form, it needs more fertilizer and water. For overly vigorous prickly ash trees, planting sweet potato can make them stop growing earlier; but for trees bearing a large amount of fruit, it can easily affect later growth. Because sweet potato has strong adaptability and high yield, it is a commonly used intercrop in prickly ash orchards. However, when sweet potato grows vigorously, its green leaves completely cover the ground, and very little light is reflected from the ground to the tree canopy, so the inner canopy and lower part of the canopy appear to have insufficient light, and fruit coloring is poor.

Potato has a relatively shallow root system, a short growth period, and an early sowing period, so the conflict with prickly ash trees over light is relatively small. As long as attention is paid to increasing fertilizer and irrigation, both can achieve a good harvest. Therefore, it is a commonly used intercrop in prickly ash orchards on flat land with good fertilizer and water conditions.

Wheat, barley, and others are also used for intercropping in prickly ash orchards. These crops are not very tall, mainly grow in spring, and have dense fibrous roots that can increase soil aggregate structure. In addition, wheat and barley themselves have relatively high economic value. However, because wheat and barley crops have deeper root systems and strong fertilizer uptake, they easily compete with prickly ash trees for fertilizer and water in early spring. Therefore, when used for intercropping, fertilizer and water should be increased, which can reduce the adverse effects on prickly ash trees.

Intercropping prickly ash trees with vegetables is relatively beneficial to the fruit trees because of careful cultivation and more adequate fertilizer and water. However, planting vegetables in autumn that need more fertilizer and water or mature late can easily prolong the growth of prickly ash trees, which is unfavorable for overwintering and often causes new shoots to “dry up” or trees to die; at the same time, it easily increases damage by leafhoppers to prickly ash branches.

Intercrops should be planted at a certain distance from prickly ash trees, usually limited to the outer edge of the canopy, otherwise it will have adverse effects on both the prickly ash trees and the intercrops. Young prickly ash trees have underdeveloped root systems and a weak ability to compete with intercrops for fertilizer and water, so intercrops should be planted closer to the canopy. Large trees have developed root systems, so intercrops can be planted farther from the canopy. In addition, where fertilizer and water conditions are good, the prickly ash tree trunks are taller, the root systems are deeper, and the canopy branches are sparse, intercrops can be planted closer to the trees.