Plant Residual Management in different Crop Rotations System on Potato Tuber Yield Loss Affected by Wireworms

Selection a proper crop rotation based on environmental conservation rules is a key factor for increasing long term productivity. On the other hand, the major problem in reaching agricultural sustainability is lack of soil organic matter. Recently, a new viewpoint has emerged based on efficient use of inputs, environmental protection, ecological economy, food supply and security. Crop rotation cannot supply and restore plant needed nutrients, so gradually the productivity of rotation system tends to be decreased. Returning the plant residues to the soil helps to increase its organic matter and fertility in long-term period. Wireworms are multi host pests and we can see them in wheat and barley too. The logic way for their control is agronomic practices like as crop rotation. Wireworms’ population and damages are increased with using grasses and small seed gramineas in mild winters, variation in cropping pattern, reduced chemical control, and cover crops in winter. In return soil cultivation, crop rotation, planting date, fertilizing, irrigation and field health are the examples for the effective factors in reducing wireworms’ damage.
In order to study the effect of crop rotations, residue management and yield damage because of wireworms’ population in soil, this experiment was conducted using four rotation systems for five years in Jolgeh- Rokh agricultural research station. Crop rotations were included, 1) Wheat monoculture for the whole period (WWWWW), 2) Wheat- wheat- wheat- canola- wheat (WWWCW), 3) Wheat- sugar beet- wheat- potato- wheat (WSWPW), 4) Wheat- maize- wheat- potato- wheat (WMWPW) as main plots and three levels of returning crop residues to soil (returning 0, 50 and 100% produced crop residues to soil) were allocated as sub plots. This experiment was designed as split plot based on RCBD design with three replications. After ending each rotation treatment, the field was sowed with potato cv. Agria in each plot in 2011. At the harvest time tuber yield and also percent and severity of infection was determined. All data was analyzed statistically and Duncan test was used for comparison of means.
Analysis of variance results showed that, potato tuber yield was affected by the crop rotation, the rate of returning residues, and also interaction between rotation × returning residues statistically (P≤0.01).When 1000 tuber was considered, analysis of variance results showed, crop rotation had a very significant effect (P≤0.01) on number and percent of infected tubers to wireworm and its holes. The most infected tubers ie.42.34 and holed i.e. 61.4 and totally 4.24% of tubers were belonged to the rotation 2, where in the rapeseed crop was preceding plant. The least one was achieved in rotation 1, with the rates of 27, 37 and 2.8% where in potato crop was not planted previously. The most infection to wireworm was found in 100% residue returning to the soil with 3.8% and the least one in no residue returning to the soil, i.e. 3.4 %. Results showed with increasing residue returning to the soil, the damage of wireworms is increased too.
Generally applying crop rotation using different crops and residue returning to the soil is resulted in higher potato tuber yield. This increasing rate for tuber yield was 116% and 57 % when the preceding crops were wheat and rapeseed respectively compared to the mean of rotations 3 and 4. For the aim of sustainable production of potato and reducing of wireworm damage it is necessary we focus on other crop rotation and the importance of C:N ratio and the rate of residue returning to the soil. So we need to conduct new experiments with these purposes.