Possible Controlling Effects of Cover Crops on Weeds in Subsequent Cultivation (Corn) under Different Tillage Methods
In order to investigation of possible controlling effects of cover crops on weeds in subsequent cultivation (Corn) under Different Tillage Methods, two factorial experiment based on randomized complete block design were carried out in Karaj, Iran, in 2006, in two separate parts of a farmland considering great variations in growth and diversity of weeds. The main factor was cover crops including control (without crop cover), hairy vetch, Persian clover and rye and the second factor was planting date of cover crops under surface or disk tillage and common or moldboard tillage. One experiment was done before corn cultivation according to initial plot plan under disk tillage and another one was carried out under moldboard tillage with cultivation of corn SCK108. Results showed that inhibition potential of these two crops is higher due to higher N content of their aerial and root system (residue) that lead to increase in mean mineral and organic N content under disk tillage. It is possible that released inhibitors with higher remained N in soil had toxicity effects on weed germination, so that weed plant number and density decreased with the increase in N content of vetch and clover residue. The plant number of these weeds significantly decreased through planting vetch, Persian clover or rye as cover crop under surface tillage compared to control. Their TDW in the presence of vetch and Persian clover was significantly lower than that in the rye and control treatments under same tillage method. Similarly, soil mineral N content in the depth of 20-40 cm aggregately in three planting date under disk tillage in vetch and clover treatments was significantly higher than that in rye treatment that corresponds to the status of weeds. The amount of mineral N content was highest in rye treatment among all treatments under moldboard tillage. Among two kinds of tillage, surface or disk tillage had better results compared to common or moldboard tillage. It seems that nowadays surface tillage by different implements was extensively used in the cultivation of different crops under different conditions.
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