Green Control Measures of Weeds in Wheat Fields in Hetao Irrigation Area along the Yellow River

Lei YANG Jing LIU Ruiqiang WEN Peizhi ZHANG Chang LIU Aiqing WEN Jiancheng ZHANG Chunzhi ZHAO Huijuan ZHANG Hongxu ZHANG Guoqiang LI

Abstract This study was conducted to solve the problem of green weed control in wheat fields in Hetao irrigation area among the Yellow River. Based on the observation of the competition between wheat and weeds in areas where weeds occurred seriously in wheat fields in Hetao irrigation area among the Yellow River, we measured the effects of green weed control measures and wheat yield using different wheat varieties, planting densities, different organic fertilizers, different ploughing times, and different mulching methods. The results showed that the emergence of weeds in wheat fields dominated by Chenopodiaceae weeds, grain amaranth and barnyard grass was more than 10 d later than wheat. Weeds were mainly distributed between rows (holes), and the number of plants accounted for 66.6% (drill seeding) and 97.6% (hole seeding), respectively. And the growth of weeds in rows (holes) was weaker, and the fresh weight of individual plants was 39.3%-41.9% lower than that between rows (holes). The ecological weed inhibitory effect was significant in the early stage of wheat growth; and among the green weed control measures, except that different varieties and planting densities caused no significant difference in weed control effect, other measures had obvious weed control effects. Comprehensive comparison showed that the control effects of plant number in black film full-covered hole seeding, conventional film-covered hole seeding, increasing ploughing times, and applying organic fertilizer free of weed seed pollution were 82.3%, 71.7%, 22.0%, and 8.6%, respectively; the fresh weight control effects of black film full-covered hole seeding, conventional film-covered hole seeding, increasing ploughing times, and applying organic fertilizer free of weed seed pollution were 98.0%, 97.1%, 23.9%, and 9.6%, respectively; and the fresh weight control effects of black film full-covered hole seeding, conventional film-covered hole seeding and increasing ploughing times increased wheat yield by 69.4%, 56.4% and 21.1%, respectively. The technologies in this study can realize the purposes of mechanized green weed control in organic wheat production and low-cost, high-yield, large-scale production.

Key words Hetao irrigation area along the Yellow River; Wheat weed; Green control; Organic wheat; Film mulching hole seeding

Received: August 21, 2021  Accepted: October 29, 2021

Supported by Science and Technology Cooperation Project between Bayannaoer Academy of Agricultural and Animal Sciences and Bayannaoer Municipal Government (2020BCN886); 2020 Science and Technology Major Special Project of Inner Mongolia Autonomous Region (NMKJXM202013); Inner Mongolia "Grassland Talents" Engineering Team (CYYC2019-2-50).

Lei YANG (1987-), male, research assistant, master, devoted to research about wheat genetic breeding and cultivation technology.

*Corresponding author. E-mail: yanglei0301@126.com.

Wheat ( Triticum aestivum  L.) is one of the three major food crops in China, as well as an important commodity grain and strategic reserve grain. Wheat production is directly related to China’s food security, as well as the increase of agricultural efficiency and farmers’ income in wheat-producing areas［1］. Hetao irrigation area along the Yellow River is one of the most important producing areas for high-quality wheat in China. Hetao wheat and its flour have been well-known at home and abroad［2］. However, weed seeds carried by Yellow River water irrigation and high groundwater level in Hetao irrigation area are very conducive to the growth of weeds. As a result, the harm of weeds in the wheat fields in Hetao irrigation area has always been serious, and chemical weeding in wheat fields has also become a must for wheat production. Long-term use of herbicides will not only make weeds resistant to various herbicides［3-5］, but also bring environmental pollution problems［5-7］, and it simultaneously hinders the pace of organic and high-quality production in high-quality wheat producing areas. If we want to achieve organic production, we can only depend on manual weeding. However, the problems of manual weeding are: high cost, difficult to fine labor, incapable of eradicating weeds in time, low yield, and impossible large area promotion. Therefore, solving the technical problems of green weed control in wheat fields in Hetao irrigation area along the Yellow River［8-9］ has become the technical key to realize organic production of high-quality wheat in Hetao, and even the second take-off of the high-quality wheat industry, and is of great significance to the revitalization of the agricultural industry in Hetao irrigation area along the Yellow River.

Studies related to the prevention and control of farmland weeds have shown that the seeds of farmland weeds mainly come from soil［10-11］, and about 60% of wheat field weeds in Hetao irrigation area along the Yellow River also come from soil［6,12］. At present, in addition to manual weeding, related green weed prevention and control measures also include: adopting different rotation and farming systems to reduce farmland weeds［13-15］, realizing the purpose of ecological weed control, labor saving, high yield and high efficiency in forage planting according to ecological principles such as niche competition［16-17］, and controlling weeds in vegetable, maize, and rice fields and realizing organic production by low-transmittance black film mulching and crop rotation agricultural measures［18-21］. However, there are few reports on the green control of weeds in wheat fields in Hetao irrigation area along the Yellow River. In this study, based on the weed control theory of "cutting off the sources, intercepting the flow and exhausting the bank"［6,10］, different agricultural green weed control tests were set, and green control measures of weeds in wheat field in Hetao irrigation area along the Yellow River were put forward through the observation of the competitive relationship between crops and weeds, aiming to provide theoretical and technical support for solving the problem of green weed control in wheat fields in Hetao irrigation area along the Yellow River.

Materials and Methods

General situation of the experimental area

The experimental site was located in Yuanziqu Test Base of Bayannaoer Academy of Agricultural and Animal Sciences (107°07′ E, 40°51′ N, 1 024 m above sea level) in Chunguang Village, Shanba Town, Hangjinhou Banner, Bayannaoer City, Inner Mongolia. This area was provided with well-Yellow River double irrigation facilities, that is, open channel Yellow River water irrigation and pumped well underground water pipeline irrigation. The test site (0-20 cm soil layer) had loamy soil, containing organic matter 20.8 g/kg, total nitrogen 1.16 g/kg, available phosphorus 28.9 mg/kg, available potassium 120 mg/kg, and total salt 0.7 g/kg, with a pH at 7.5.  The previous crop was wheat, and the weeds were evenly distributed and occurred severe (total weed density 200-246 plants/m2). The dominant weeds were  Chenopodium album  L,  Amaranthus hypochondriacus  L, and  Echinochloa crusgalli  (L.) Beau［12］.

Experimental materials

The wheat variety used in the experiment was "Yongliang No. 4", the main cultivar in Hetao area, which is of the high-quality short-stalk type (plant height 83-85 cm). High-stalk variety "Neimai 17" (plant height 95-100 cm) was added to the weed-inhibiting test of different varieties. Two kinds of fertilizers used in experimental treatments were self-made fully-decomposed sheep manure organic fertilizer and the organic fertilizer of the experimental sheep farm of the Academy of Agricultural Sciences (containing organic matter 24%-27%, nitrogen (N) 0.7%-0.8%, phosphorus (P2O5) 0.45%-0.60%, potassium (K2O) 0.4%-0.5%). The mulch was national standard black mulch with a width of 1.7 m and a thickness of 0.01 mm. The ploughing machine was a conventional production machine, and the planters were a conventional (with gap) film-covering hole planter, a full film-covering hole planter［22］ and a drill planter. A common residual film recovery machine was used for plastic film recovery.

Experimental design

In 2014, open-field drill and open-field hole seeding treatments were 0.13 hm2 each, and the temporal and spatial distribution of wheat and weeds and their competitive relationship were observed. In 2015, five groups of weed green control tests (shown in Table 1) were set up: ① three treatments with wheat seeding rates of 375, 412.5, and 450 kg/hm2, ② two treatment tests of short-stalk "Yongliang 4" and high-stalk "Neimai 17", ③ two treatment tests of applying 15 t/hm2 of ordinary farm manure and weed seed pollution-free organic fertilizer as the base fertilizer, ④ two treatment tests of performing autumn ploughing once after wheat harvest and performing ploughing twice with  irrigation in the middle, and ⑤ three treatments of conventional film-covered hole seeding with gaps between the film pressed with soil on the side (hereinafter referred to as "conventional film-covered hole seeding"), shown in Fig. 1, full film-covered hole seeding with no gaps between the film pressed with soil on the surface (hereinafter referred to as "full film-covered hole seeding"), shown in Fig. 2, and seeding in drill. The areas of the test plots were all 30 m2, and they were all randomly arranged and repeated 3 times.

Planting and management

Except for corresponding special sowing and field operations in accordance with the treatment requirements, chemical herbicides, manual pulling of weeds, and chemical fertilizer application were not carried out in the test area. In the film-covered test areas, a residual film recovery machine was used to recover residual film after wheat was harvested. Other field management was carried out in accordance with local conventional wheat planting management methods.

Investigation methods

In the observation experiment on the temporal and spatial distribution of wheat and weeds growth and their competitive relationship, five sample points were randomly selected for weed density investigation, and the size of the sample points was 1 m2. From the beginning of April, we began to investigate main weed species and their number of plants and plant height every 10 d, and wheat density and plant height were recorded at the same time. In late May, the fresh weight of weeds between rows (holes) and that of weeds mixed in wheat seedlings were investigated.  Before wheat was harvested, five sample points were randomly selected from each plot in the weed green control experimental areas for the recording of number and fresh weight of weeds, and the size of point was 1 m2. For tests ④ and ⑤ with better weed control effects, wheat yield component factors were investigated, and the yield was measured.

Statistics and analysis

Excel was used for preprocessing the investigation data. Statistical T-test, analysis of variance and multiple comparisons were performed on the data based on SPSS 22.0. Origin 2019 software was used for graphing.

Results and Analysis

Emergence time of wheat seedlings and weeds

The observation results of the main weeds in wheat fields and the emergence of wheat seedlings are shown in Fig. 3. The seedlings of wheat reached the condition of tidy seedlings in mid-April, while the seedlings of main weeds such as wheat field quinoa, barnyard grass, and grain amaranth all emerged later than wheat. Quinoa emerged about 10 d late, and the seedlings emerged quickly in late April and the seedling quantity was higher than those of barnyard grass and grain amaranth. Barnyard grass and grain amaranth were about 30 d late, and the emergence process was gentle. The heights of all kinds of weeds were lower than the height of wheat plants before mid-June, after which quinoa and grain amaranth were higher than wheat quickly, making the damage worse (Fig. 4). The relative hysteresis of weed growth provides conditions for ecological control of weeds.

Lei YANG  et al.  Green Control Measures of Weeds in Wheat Fields in Hetao Irrigation Area along the Yellow River

Spatial distribution of weeds in wheat fields

The spatial distribution of weeds in wheat fields was investigated (Fig. 5). The results showed (Table 2) that there were significant difference in proportion and growth rate between weeds mixed with wheat seedlings and weeds between rows (holes). In late May, the fresh weight of weeds between rows in the fields of drill-seeded wheat reached 76.6%, and the proportion of weeds between holes in the fields of hole-seeded wheat reached 98.6%, indicating that weeds in wheat fields mainly occurred between rows (holes), and the growth of weeds in rows (holes) was weak. The fresh weight of individual plants was 39.3%-41.9% lower than that between rows (holes), which meant that wheat seedlings had a significant inhibitory effect on weeds. It showed that controlling weeds between rows (holes) is the main strategy to control weeds in whole wheat fields.

Effects of different green weed control measures

Weed control effect of wheat variety and seeding rate regulation (joining stage)

The results on the weed control effects of varieties with different plant heights and different planting densities showed (Table 3) that increasing seeding rate had a tendency to inhibit the growth of the number of weeds, and planting the tall-stalk variety had a certain inhibitory effect on weeds before filling. However, the results of the analysis of variance on the two measures were not significant, indicating that increasing sowing rate and planting high-stalk varieties have limited inhibitory effects on weeds and it is difficult to fundamentally control weeds.

Weed control the effect of ploughing, fertilization and mulching

The results of green control measures for weeds showed (Table 4) that increasing one time of ploughing after wheat harvest significantly reduced weed damage compared with conventional ploughing. Specifically, the number of weeds was reduced by 22.0%, and the fresh weight was reduced by 23.9%. Replacing ordinary farmyard manure by organic fertilizer free  of weed pollution could significantly reduce the occurrence of weeds in the very year. Specifically, the plant control effect before wheat harvest was 8.6%, and the control effect of fresh weight was 9.6%. The comprehensive weed control effects were very significant in black full-covered hole seeding (Fig. 2) and conventional film-covered hole seeding (Fig. 1), the plant control effects of which were 82.3% and 71.7%, respectively, and the fresh weight control effects were 98.0% and 97.1%, respectively.

Effects of green weed control measures on wheat yield

The effects of different green prevention and control measures for weeds on the yield traits of wheat were analyzed. The results showed that film-covered hole seeding increased the number of ears per unit area, the number of grains per ear, and the 1 000-grain weight compared with drill seeding, full film-covered hole seeding increased the number of ears per unit area compared with conventional film-covered hole seeding, and the control measures of full film-covered hole seeding, conventional film-covered hole seeding and increasing ploughing times increased wheat yield by 69.4%, 56.4%, and 21.1%, respectively (Table 5).

Discussion

Weeds are the main factor affecting the yield of organic agricultural crops［23］, and effective control of weeds plays an important role in the development of organic agriculture. Crop competition plays an important role in the control of weeds in wheat fields［24］. Based on the observation of the competition relationship between wheat and weeds, this study determined the weed control effects of different green weed control measures.

For black film-covered hole-seeded wheat in Hetao irrigation area along the Yellow River, weed seeds in the soil can germinate but are difficult to grow normally through the light blocking effect of black film covering, which not only achieves the purpose of controlling weeds and reducing damages in the current season, but also accelerates the reduction of the soil seed bank and reduces the damage to subsequent crops. For organic production fields that can only be applied with organic slow-release fertilizers, the warming and moisturizing effects achieved by mulching the soil improves microbial activity and the utilization efficiency of organic fertilizer［25-26］. Due to the dual effects of controlling weeds and improving fertilizer efficiency, its organic wheat can realize mechanized production, which not only greatly increases wheat yield, but also greatly reduces production costs. The promotion and application prospects of black film-covered hole seeding are broad. As to increasing one time of ploughing, although the effects on reducing the seed bank and reducing the density of weeds in the current season are not very high, the effect of increasing wheat yield is also very significant because the fertility increases by weeds turned into the soil and soil physical properties become better［27-28］, so it has great application value for plots where other crops are no longer planted after wheat. In this study, due to the limitation of the test site, the species of weeds were not complete enough, and the control effect of other weeds could not be tested, that is, the experimental conclusion has certain limitations. However, the technology of this study uses physical measures such as plastic film covering and ploughing the land to control weeds, which have low selectivity for weeds and should have the characteristics of wide adaptability. Therefore, even in plots where weed species are alienated, it should have a good reference significance. The application of this technology requires plastic mulching, which increases the cost of wheat plant materials and also increases the risk of plastic film pollution. Even though residual film in wheat fields has a shorter coverage time than crop fields such as maize and sunflower and good toughness during recovery, the stubbles are small and easy to separate from the mulching film, and the recovery is thus relatively easy, special residual film recovery machinery is also required for recovery. Therefore, it should be fully considered when promoting.

Conclusions

Based on the observation of the competition relationship between wheat and weeds in the area where weeds in wheat fields occurred seriously in Hetao irrigation area along the Yellow River, this study determined the effects of green weed control measures including using different wheat varieties, planting densities, different organic fertilizers, different ploughing times, and different mulching methods on wheat yield. The results showed that among the green weed control measures, except that different varieties and planting densities did not cause significant differences in the effect of weed control, other measures had obvious weed control effects. The plant number control effects of black film full-covered hole seeding, conventional film-covered hole seeding, increasing the times of ploughing and applying organic fertilizer free of weed seed pollution were 82.3%, 71.7%, 22.0%, and 8.6%, respectively; and the yield increases of black film full-covered   hole seeding, conventional film-covered hole seeding and increasing ploughing times were 69.4%, 56.4% and 21.1%, respectively. This study can provide a theoretical basis for accelerating the realization of mechanized green weed control in organic wheat production.

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