cover crops

This study was conducted to evaluate the effects of summer cover crops used as green manure on wheat yield and selected soil physicochemical properties in a wheat-based rotation system over two growing seasons (2019-2021). The research also examined how different treatments influenced soil organic matter dynamics and their subsequent effects on wheat yeild.

The experiment was conducted as a randomized complete block design with three replications over two growing seasons (2019-2020 and 2020-2021) at the Karaj Research Station. The experimental treatments included 16 cover crops that were cultivated after wheat harvest and used as green manure. Wheat was subsequently planted, and the yield of each treatment was measured after harvest. Soil samples were collected from each treatment plot and analyzed in the laboratory to determine organic matter content and physicochemical properties. 

The biomass of cover crops showed significant differences. Sudan grass and cowpea had the highest biomass, while barley and rye had the lowest. No significant differences in wheat grain yield were observed among different treatments over the two years. However, the composite analysis revealed a 21% increase in wheat yield in the second year compared to the first year. Soil organic carbon content increased by 0.35% over the two years. Mung bean and cowpea had the highest increase in soil organic matter and the highest effect on C/N ratio, respectively. Safflower had the greatest effect on increasing the amount of absorbable phosphorus in the soil, and clover and mung bean had the greatest effect on increasing the amount of absorbable potassium in soil. 

Cover crops have different effects on various soil components. The consecutive use of cover crops as green manure increased yield over two years. High biomass production alone cannot be the sole criterion for selecting cover crops as green manure; attention should be paid to their effects on soil properties, especially soil organic carbon.

This study was performed to investigate the effect of nitrogen fertilizer levels and pre-planting of cover crops on some vegetative traits and yield of rice plants.

This was conducted over 2017-2018 and 2018-2019, at the research farm of Sari University of Agricultural Sciences and Natural Resources. The experimental design employed a three-replicated split-plot arrangement within a randomized complete block design. The main plots involved five nitrogen consumption levels (0, 120, 240, 320, and 400 kg ha-1). The sub-plots included four types of pre-planted cover crops (no cover crop, canola, bersim clover, and rye).

Based on the findings, employing berseem clover as a cover crop in pre-sowing resulted in a significantly more favorable rice yield than others. Nitrogen fertilizer at rates of 320- 400 kg ha-1 led to enhanced vegetative traits, yield, and various yield components, including leaf area index and tiller number, ultimately resulting in increased overall yield. Results revealed that planting bersim clover cover crop before planting rice, along with 320 kg ha-1 of urea fertilizer, leads to 41.5% higher yield compared to no fertilizer).).

Bersim clover stood out among the pre-planting cover crops, significantly enhancing many rice traits. Additionally, no significant difference was observed between urea fertilizer levels of 320 and 400 kg ha-1 in several measured traits. Thus, the integrated treatment of bersim clover cover crop and 320 kg ha-1 of urea fertilizer is recommended before planting rice.

Use of cover crops for controlling weeds is an environmental friendly alternative to conventional chemical and mechanical methods. Kohlrabi is a cool-season hardy crop which can be grown in early spring. The crop is well known in Europe and other regions as a health staple in human’s diets. The aim of the present study was to investigate the effectiveness of using sunn hemp and rye cover crops as monoculture or mixed in controlling weeds and improving yield of kohlrabi.

A two-year field study was conducted. Experimental treatments consisted of monoculture rye (Secale cereal L.), sunn hemp (Crotalaria juncea) and their mixture and no cover crop as control.

Cover crops biomass were 379.7 and 473.9 g.m-2 in first and second growing seasons, respectively. Averaged over two years, weed dry weight reduced by 52.6, 42.5 and 45.4 percentage in rye monoculture, sunn hemp monoculture, and mixed cover crops, respectively. Monoculture rye was more effective in suppressing the dominant weeds. Rye reduced lambsquarter, pigweed, and wild mustard by about 44, 60, and 52 percentage, respectively. On average, use of cover crops improved kohlrabi yield by 30%. Sunn hemp followed by mixed cover crops were more effective in kohlrabi yield improvement.

Cover crops provide many ecological benefits. When weed suppression is the main goal of cover cropping, rye with fast growing habit and extensive root system is more efficient. However, legumes or mixture of legumes and grass are more effective in crop yield improvement.

Cover crops are one of the alternative methods to reduce chemical inputs to control weeds. The aim of this study was to investigate the ability of weed control by cover crops in monoculture and dual and triple intercropping as well as their effect on iceberg lettuce (Lactuca sativa var. Ice berg) yield. 

Methods & Materials:

A field experiment in the form of randomized complete block design with three replications was conducted in 2017 in the research field of the Faculty of Agriculture, Mohaghegh Ardabili University. Experimental treatments include cultivation of barley cover crops (Hordum vulgare L.), sunnhemp (Cartalaria juncea) and buckwheat (Fagopyrum esculentum) as monoculture (100% of recommended seeds) and dual and triple intercropping (50 and 33.3% of the recommended seeds, respectively).  

The results showed that the highest biomass of cover crops was obtained from barley monoculture treatments and it’s intercropping with sunnhemp (1323.25 and 1247.14 g.m-2, respectively). The lowest weeds biomass (115.75 g.m-2) was belonged to sunnhemp + buckwheat. The highest lettuce fresh yield (7207 g.m-2) was obtained from barley + buckwheat + sunnhemp. The results of this experiment showed that double and triple intercropping of barley, sunnhemp and buckwheat compared to monoculture and control treatment had more effective control over Chenopodium album, Circium arvense, Amaranthus retroflexus and Sinapis arvensis.  

From the results, it can be concluded that cover crops in double and triple intercropping based on the obtained weed biomass have a better ability to control weeds.

Increasing our knowledge of environmental hazards and resistance to herbicides while avoiding high costs has led to the use of applied approaches that pose minimal danger to the agroecosystem and reduce herbicidal pollution. Living mulches are plants from the Fabaceae family that are used as cover crops. Since cover crops uptake water and nutrients from the soil, they require appropriate management to reduce their competition with the main crop and prevent lost yield. Thus the growth rate, density and other effective growth factors of living mulch is important. The objectives of the experiment were to investigate the impact of using berseem clover (Trifolium alexanderinum) and trigonella (Trigonella foenum-graecam) as cover crops on the yield and yield components of wheat as well as weed reduction.
Material and In order to investigate the effect of using berseem clover (Trifolium alexanderinum) and trigonella (Trigonella foenum-graecam) as cover crops on the yield and yield components of wheat and weed control, an experiment was carried out in a randomized complete block design with eight treatments and three replicates in the autumn of 2011, in Behshahr, Iran. Treatments included a wheat planting distance of 20 cm and 30 cm with and without the presence of berseem clover and trigonella as cover crops. These were planted both in areas with weeds and without. The weed flora of the field included wild oat (Avena fatua L.), Milk thistle (Silybium marianum) and hairy vetch (Vicia villosa Roth). A sampling was carried out in order to evaluate wheat dry matter and density, the biomass of weeds, and the dry matter of cover crop. Variations in wheat and cover crop height were investigated by using the Gompertz sigmoidal model (Draper and Smith, 1981). Data were subjected to analysis of variance and means were compared with Duncan's test.
The results of the experiment showed that wheat in the presence of trigonella had a higher level of dry matter (419.39 g m-2), and higher economical (5,390 kg ha-1) and biological yield (16,256.70 kg ha-1). The wheat yield from the 20-cm plantings in all treatments was more than in the 30-cm plantings. The root of Fabaceae plants, by penetrating the soil deeply, improve and enhance the microorganism population and by biological nitrogen fixation that supply the nitrogen requirements of the main crop (Naghizadeh and Ghalavi, 2012). Moreover, cover crops through the uptake of nitrogen and nutrients prevent their leaching (Ranells and Wagger, 1984). The dry matter and height of trigonella both in the 20-cm and 30-cm plantings was higher than berseem clover. The reduction of weed biomass in the treatment with trigonella was higher than the treatments with berseem clover used as a cover crop. This result shows that trigonella is better able to adapt to the environmental growth conditions in wheat canopy compared to berseem clover and could be a suitable cover crop for wheat (Sabahi et al., 2006). Weed biomass in the 20-cm wheat planting was lower than in the 30-cm planting.
Generally, both cover crops were successful in weed control and enhancement of wheat yield compared to a wheat monoculture. Trigonella, however, was more efficient than berseem clover in reducing weed growth and enhancing wheat yield. The results obtained from the research could be used in sustainable management practices to reduce weed growth and herbicide application in wheat fields.

In order to evaluate the use of cover crops to control weeds in forage corn، an experiment with a factorial arrangement based on a randomized complete block design with three replications was conducted in 2012at the Agricultural Research Station (Samian) in Ardabil. The first factor included different cover crops comprising rye، hairy vetch، clover and no cover crop، plus a plot without weed control. The second factor consisted of nitrogen splits of 225 kg urea per hectare with two levels، the first level (1/2 at sowing + 1/2 in the 8 to 10 leaf stage of corn)، the second level (1/3 at planting + 1/3 in the 8 to 10 leaf +1/3 a week before tasseling of corn) to the desired split in two، and three corn growth stages were used. The third factor consisted of two levels of weed sampling frequency at 60 days and 90 days after planting corn. Combined analysis of variance showed that the rye cover crop، hairy vetch and clover reduced the biomass of annual weeds of Chenopodium album L. and Amaranthus retroflexus L. at about 95، 88 and 70 percent and 81، 77 and 60 percent compared to the control، respectively. Also decreased weed densities of about 67، 52 and 32 and 68، 55 and 26 percent، respectively، were identified. In addition، these cover crops reduced biomass of perennial weeds of Convolvulus arvensis and Cynodon dactylon compared to control، at about 82، 79 and 62 and 77، 73 and 57 percent، and density of about 57، 53 and 32، and 65، 55 and 31 percent، respectively. Cover plants and split nitrogen interactions have significant effects on fresh corn forage. The highest fresh yield of forage corn (51307 kgr per hectare) was obtained from full weeding. After weeding treatments، forage yield in hairy vetch treatment significantly was more competent than the other cover crops. In general، taking into account the interests of more effective control of weeds and forage production، treatment of hairy vetch cover crop and the second split of nitrogen fertilizer level was found to be appropriate.

In order to study different times of cultivating and type of medical and cover plants on performance and weed biomass of corn (single cross 504), the experiment was carried out in 2010- 2011 in research farm of the agriculture faculty of university of Tabriz. The experiment was carried out in a factorial arrangement with the base of randomized complete block design in three repetications. The treatments of this experiment included type of medical and cover plant in 4 levels (Clover, hairy vetch, basil and dill) as first factorial and time of cultivating cover and medical plant in tow levels(synchronic cultivation with corn and cultivation 15 days after corn cultivation) as second factorial. The results showed that the ear height, the number of grain row per ear and yield of grain lied under effect of the time of cultivation and the type of cover plants as the highest amount of these traits were seen in treatment of the corn with clover and the lowest amount were seen in the treatment of the corn with dill. Treatment composition of cover plant × the time of cultivation on ear diameter and weight of 100 grain was significant and in both traits, ear diameter and weigh of 100 grain, the treatment of synchronic cultivation of corn with clover and the treatment of dill with 15 days delay in comparison of the cultivation of corn had the highest and lowest amount, respectively. Also, the highest weed biomass was seen in dill treatment with 15 delay than corn cultivation and the lowest amount was seen in synchronic cultivation of clover with corn.