Effects of Plant Residues in Two Types of Soil Texture on Soil characteristics and corn (Zea mays L.) NS640 Yield in a Reduced -Tillage cropping System

IntroductionThe impact of agronomy on the subsequent product in rotational cropping systems depends on factors such as plant type, duration of crop growth, soil moisture content, tillage type, irrigation method, the amount of nitrogen fertilizer, quantity and quality of returned crop residues to the soil. Prior cultivated crops improve the next crop yield by causing different conditions (nitrogen availability, organic matter and volume of available water) in soil. This study was conducted due to importance of corn cultivation in Khuzestan and necessity of increasing the soil organic matter, moisture conservation and in the other hand the lack of sufficient information about the relationship between soil texture, type of preparatory crop in low-tillage condition and some soil characteristics and corn growth habits. The purpose of this experiment was to evaluate the effect of residue of preparatory crops in low plowing condition in two soil types on corn yield and some soil characteristics.
Materials and MethodsThis experiment was carried out at Shooshtar city located in Khuzestan province. An experiment was performed by combined analysis in randomized complete block design in two fields and in two consecutive years with four replications. Two kinds of soil texture including: clay loam and clay sand. Five preparatory crops including: broad bean, wheat, canola, cabbage and fallow as control assigned as sub plots. SAS Ver. 9.1 statistical software was used for analysis of variance and comparison of means. Graphs were drawn using MS Excel software. All means were compared by Duncan test at 5% probability level.
Results and DiscussionThe soil texture and the type of preparatory crop influenced the characteristics of the soil and corn grain yield. Returning the broad bean residue into two types of soil caused the highest grain yield of corn 10128.6 and 9547.9 kgha-1, respectively. The control treatment in sandy loam texture had the lowest corn seed yield (6111 kg.ha-1). Therefore, in these conditions, amount of plant residues and soil texture have played an important role in improving the soil quality and corn yield, which would be lead to economic objectives of sustainable and low input and cost production. Treatment of broad bean residues in depth of 0-15 cm resulted to the highest total nitrogen of 0.121% in clay loam soil and 0.122% in loam sand soil. The return of broad bean plant residues in both soil types improved corn grain yield which can be attributed for fixing and increasing the soil nitrogen by broad bean and decrease the ratio of carbon to nitrogen in soil. It seems that the contribution of broad bean residues released nitrogen gradually, particularly at the end of corn growing season.
The results showed that treatment of wheat residues in clay loam soil had the highest carbon to nitrogen ratio (8.10%), and in sandy loam soil, treatment without plant residues had the lowest ratio of carbon to nitrogen (1.4%). Increased carbon/nitrogen ratio was the result of high ratio of carbon content to nitrogen in wheat. Burying the remains of wheat and canola led to significant decrease in soil nitrogen during growing season and a sudden increase in soil organic carbon.
Mean comparisons showed that adding wheat residues to clay loam soil had the lowest soil bulk density in depth of 0-15 cm (1.19 gcm-3) and treatment of control (no adding plant residues) to sandy loam soil had the highest soil bulk density (1.54 gcm-3). The lowest soil bulk density was observed in depth of 0-15 cm and with increase in depth, soil bulk density increased, too. It seems that high percentage of the soil moisture can lead to low soil bulk density. Combination of clay loam soil with wheat, canola and broad bean residues caused soil moisture content of 21.3%, 20.4% and 20.5%, respectively, while returning the residue of cabbage did not have a significant influence on soil moisture in comparison with control (12.9%).
ConclusionsIn general, mixture of broad bean residues with both soil types had the positive effects on corn yield and soil characteristics compared to other crop residue.