Four sprays and one drainage during the peanut pod-filling maturity stage to promote high yield
The pod-filling maturity stage of peanuts refers to the period from when half the plants have plump pods until most pods are fully filled and plump, that is, the period leading up to maturity and harvest. For medium-maturing varieties this lasts about 35-45 days; very early and early maturing varieties are shorter, and late-maturing varieties are longer. Summer-sown peanuts are comparable to or slightly longer than spring-sown peanuts of the same variety. In Shandong and Hebei, the pod-filling maturity stage of spring peanuts runs from early August to mid-September, and that of summer-sown peanuts from late August to early October. The pod weight gained during this period generally accounts for more than 60% of the total weight, so strengthening management at this stage can be expected to raise yields substantially.
The main tasks of field management at this stage are to slow the aging and yellowing of leaves, delay leaf drop, maintain a relatively large green leaf area and a longer functional period; enhance photosynthetic intensity, raise photosynthetic efficiency and increase the accumulation of nutrients; promote the translocation of nutrients from stems and leaves into the pods, increase the translocation rate, accelerate pod filling and form economic yield as quickly as possible; and control the damage of major diseases and pests to reduce yield losses. The main field management measures are the “four sprays and one drainage”:
1. Foliar fertilizer spraying. After peanuts enter the pod-filling maturity stage, root aging reduces their absorption capacity, and nitrogen fixation and supply by root nodules weaken, so premature leaf drop is often caused by nutrient deficiency. In the later stage, the foliar absorption capacity of peanuts increases, and timely repeated foliar spraying of fertilizer can effectively supplement nutrients and delay leaf drop, with such advantages as rapid action, high absorption and utilization rate, low input and large benefit. For the type of fertilizer, it is advisable to choose foliar fertilizers containing more phosphorus and calcium, such as “Jiataifeng” produced in Taiwan, China.
2. Spraying regulators. For fields that have not previously been sprayed with regulators or where the effect of regulators already sprayed is not obvious, spray once more with 800-1200 times dilution of “Zhuangbao'an” (be careful not to spray it onto the ground), which can noticeably thicken the leaves, deepen leaf color, delay leaf drop, accelerate pod enlargement and filling, and can also enhance drought resistance and waterlogging tolerance, and mitigate premature senescence caused by spraying paclobutrazol and regulators containing this ingredient.
3. Spraying fungicides. Leaf spot diseases, especially net blotch and brown spot, are one of the main causes of premature leaf drop in peanuts. Once they occur they spread rapidly, and often a large number of leaves drop within a few days, causing yield reduction. Combined with foliar fertilizer spraying, adding broad-spectrum fungicides such as mancozeb or thiophanate-methyl can greatly reduce the damage and delay leaf drop. Carbendazim and fungicides with carbendazim as their main ingredient are less effective and can also easily induce rust disease in the later stage.
4. Spraying insecticides. The main pests damaging peanut leaves in the later stage are leaf-feeding pests such as cotton bollworm and cotton semilooper, and leaf mites (red spider mites). The former is prone to causing damage under conditions of high temperature, frequent rain and high humidity, while the latter occurs under dry climatic conditions. Attention should be paid to inspection, and insecticides and acaricides should be sprayed for control at the young larval stage and when they occur in spots and patches. For underground pests such as white grubs, wireworms and ants, on the basis of previous control, when inspection shows larvae or damage symptoms still present in the soil layer, apply another broadcast application of quick-acting soil insecticide fertilizer powder or drench the plant hills with methyl isothiophos. Recent inspection of the amount of excrement from adult white grubs in peanut fields and the damage symptoms on the middle and upper leaves indicates that larval damage is expected to be relatively severe, so control should be strengthened.
5. Drainage and waterlogging prevention. There is more rain in the late growth stage of peanuts, and water accumulation in the field and excessive perched water in the soil plow layer are also among the causes of premature leaf drop; in severe cases they can also cause rotten pods and yield loss, so field water accumulation and plow-layer perched water should be drained promptly.
In addition, when most leaves have dropped, the top leaves and stems and branches have turned yellow, and most pods are plump, harvest should be carried out promptly. If harvest is delayed, more pods are lost, yield decreases and quality deteriorates.