Volume 14, Issue 3 (10-2024)
2024, 14(3): 53-68 |
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Ashena B, Mohammadi G, Mondani F, Boroumandan P. The Effect of Cover Crops Planted as Green Manure Pure and Mixed on Some Soil Properties and Weed Control in Potato (Solanum tuberosum L.). Journal of Crop Production and Processing 2024; 14 (3) :53-68
URL: http://jcpp.iut.ac.ir/article-1-3311-en.html
URL: http://jcpp.iut.ac.ir/article-1-3311-en.html
Respectively, Department of Plant Production and Genetic Engineering, Faculty of Agriculture and Natural Resources, Razi University, Kermanshah, Iran. , gr_mohammadi@razi.ac.ir
Abstract: (636 Views)
Extended Abstract
Introduction
Fallowing, which is one of the common practices in Iran's cropping systems, brings negative consequences such as soil erosion and reduction of its fertility, leaching of nutrients and, as a result, groundwater pollution. In addition, this practice increases weed infestation in an environment free of competition. Planting cover crops is one of the alternative methods to increase the quality and health of the soil and produce a healthy crop with minimal use of chemical inputs. Through competition and production and release of allelopathic substances in the soil environment, these crops are also considered as a suitable tool in suppressing weeds. The present study was conducted in order to investigate the effect of planting several species of cover crops as pure and mixed green manures on some soil characteristics and weed control.
Materials and Methods
This experiment was conducted in the form of a randomized complete block design with three replications in the Research Farm of Agriculture and Natural Resources Campus, Razi University, Kermanshah. Experimental treatments included cover crops of barley, common vetch and Persian clover in pure and mixed form at 10 levels: control (without cover crop), pure clover, pure barley, pure vetch, 50% barley + 50% clover, 50% barley +50 vetch, 50% vetch + 50% clover, 30% barley + 70% clover, 30% vetch + 70% barley, and 40% clover + 40% vetch + 20% barley. In order to cultivate cover crops, the land was first prepared by plowing and disk harrowing. Then, the seeds of cover crops were planted in plots of 7 × 6 m dimensions, using a furrower. The amount of seed used in the pure cultivation treatments of vetch, clover and barley was 60, 20 and 150 kg ha-1, respectively, and in the mixed treatments, different amounts of the seeds of each cover crop were planted based on the above-mentioned ratios. On the 30th of May (one month before planting potato) and at the stage when none of the cover crops had entered seed production stage, they were incorporated into the soil as green manures in two stages (one week apart) and at a depth of 10 to 15 cm.
Results and Discussion
The results showed that the cultivation of cover crops caused a decrease in pH and an increase in soil organic carbon compared to the control treatment, so that the lowest pH (7.32) and the highest soil organic carbon content (1.76%) were obtained from the pure barley treatment. Also, treatments of 40% clover + 40% vetch + 20% barley and 50% vetch + 50% clover caused a 38% and 36% increase in soil nitrogen, respectively, compared to the control treatment. The use of cover crops increased the content of phosphorus and potassium macronutrients in the soil both before and after potato harvest, compared to the control. The use of cover crops reduced the density of weeds in 20 and 40 days after potato cultivation, and the pure barley treatment reduced the density of weeds by 53 and 54%, respectively, compared to the control. The highest potato tuber yield was achieved under the treatments of 40% clover + 40% vetch + 20% barley and 50% vetch + 50% clover. The mentioned treatments increased the tuber yield by 71.09 and 59.79% compared to the control, respectively. The decrease in soil pH may be due to the accumulation of organic matter from crop residues and the acidification process during the mineralization of these residues, the increase in the amount of electrolytes, as well as the increase of microbial respiration and thereby the release of CO2 (5, 18). The increase in soil nitrogen availability following the application of green manures may have stemmed from the increase in root nodulation, release of a larger amount of nitrogen compounds by root nodules in the early stages of crop growth and their subsequent decomposition in later stages. Also, the increased nitrogen is at least partly due to the increase of organic matter through the return of biomass of cover crops in the cropping system (21). Covering the soil surface by cover crops and hence shading reduces weed seed germination and their subsequent growth due to competition of cover crops. In addition, during the decomposition of cover crop residues, allelopathic compounds are released in the soil environment, which affects the germination of weed seeds and establishment of their seedlings (15). Green manures obtained from cover crops increases moisture storage and improves soil fertility, enhancing the growth and yield of the main crop (16).
Conclusions
The results showed that the cultivation of cover crops instead of fallow increased the amount of organic carbon and macronutrients, despite decreasing the soil pH, leading to improvement in the access of the main crop to the soil nutrients. Weed control was another advantage of planting these crops. In the present study, the planting of leguminous cover crops with non-leguminous plants had the satisfactory results.
Introduction
Fallowing, which is one of the common practices in Iran's cropping systems, brings negative consequences such as soil erosion and reduction of its fertility, leaching of nutrients and, as a result, groundwater pollution. In addition, this practice increases weed infestation in an environment free of competition. Planting cover crops is one of the alternative methods to increase the quality and health of the soil and produce a healthy crop with minimal use of chemical inputs. Through competition and production and release of allelopathic substances in the soil environment, these crops are also considered as a suitable tool in suppressing weeds. The present study was conducted in order to investigate the effect of planting several species of cover crops as pure and mixed green manures on some soil characteristics and weed control.
Materials and Methods
This experiment was conducted in the form of a randomized complete block design with three replications in the Research Farm of Agriculture and Natural Resources Campus, Razi University, Kermanshah. Experimental treatments included cover crops of barley, common vetch and Persian clover in pure and mixed form at 10 levels: control (without cover crop), pure clover, pure barley, pure vetch, 50% barley + 50% clover, 50% barley +50 vetch, 50% vetch + 50% clover, 30% barley + 70% clover, 30% vetch + 70% barley, and 40% clover + 40% vetch + 20% barley. In order to cultivate cover crops, the land was first prepared by plowing and disk harrowing. Then, the seeds of cover crops were planted in plots of 7 × 6 m dimensions, using a furrower. The amount of seed used in the pure cultivation treatments of vetch, clover and barley was 60, 20 and 150 kg ha-1, respectively, and in the mixed treatments, different amounts of the seeds of each cover crop were planted based on the above-mentioned ratios. On the 30th of May (one month before planting potato) and at the stage when none of the cover crops had entered seed production stage, they were incorporated into the soil as green manures in two stages (one week apart) and at a depth of 10 to 15 cm.
Results and Discussion
The results showed that the cultivation of cover crops caused a decrease in pH and an increase in soil organic carbon compared to the control treatment, so that the lowest pH (7.32) and the highest soil organic carbon content (1.76%) were obtained from the pure barley treatment. Also, treatments of 40% clover + 40% vetch + 20% barley and 50% vetch + 50% clover caused a 38% and 36% increase in soil nitrogen, respectively, compared to the control treatment. The use of cover crops increased the content of phosphorus and potassium macronutrients in the soil both before and after potato harvest, compared to the control. The use of cover crops reduced the density of weeds in 20 and 40 days after potato cultivation, and the pure barley treatment reduced the density of weeds by 53 and 54%, respectively, compared to the control. The highest potato tuber yield was achieved under the treatments of 40% clover + 40% vetch + 20% barley and 50% vetch + 50% clover. The mentioned treatments increased the tuber yield by 71.09 and 59.79% compared to the control, respectively. The decrease in soil pH may be due to the accumulation of organic matter from crop residues and the acidification process during the mineralization of these residues, the increase in the amount of electrolytes, as well as the increase of microbial respiration and thereby the release of CO2 (5, 18). The increase in soil nitrogen availability following the application of green manures may have stemmed from the increase in root nodulation, release of a larger amount of nitrogen compounds by root nodules in the early stages of crop growth and their subsequent decomposition in later stages. Also, the increased nitrogen is at least partly due to the increase of organic matter through the return of biomass of cover crops in the cropping system (21). Covering the soil surface by cover crops and hence shading reduces weed seed germination and their subsequent growth due to competition of cover crops. In addition, during the decomposition of cover crop residues, allelopathic compounds are released in the soil environment, which affects the germination of weed seeds and establishment of their seedlings (15). Green manures obtained from cover crops increases moisture storage and improves soil fertility, enhancing the growth and yield of the main crop (16).
Conclusions
The results showed that the cultivation of cover crops instead of fallow increased the amount of organic carbon and macronutrients, despite decreasing the soil pH, leading to improvement in the access of the main crop to the soil nutrients. Weed control was another advantage of planting these crops. In the present study, the planting of leguminous cover crops with non-leguminous plants had the satisfactory results.
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