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Conventional Tillage – Moldboard Plow

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Conventional tillage management includes inversion of soil with primary tillage equipment like moldboard plow followed by secondary tillage practices such as disking or harrowing. The moldboard plowing operation involves slicing, lifting, fracturing, and inverting the soil, causing horizontal shearing. This post will describe the moldboard plow tillage practice, its benefits, and its impact on soil productivity.

A moldboard plow is a tillage equipment that cuts soil, lifts it, and turns it upside down using a curved plate or moldboard. The flat bottom’s width determines the tillage zone’s width, and the entire soil up to the set tillage depth (9-12 inches) is cut, lifted, and loosened. Moldboard plows can be designed to flip soil furrow slices by 180 degrees causing complete soil inversion. This tillage method is practiced primarily by farmers to form a more drained and looser seedbed and to bury the crop residues (80-90%), weeds, and insect pests left on the soil surface. In high-residue crop rotation systems like corn-corn production, moldboard plows can be considered highly effective in burying crop residues. 

However, these soil conditioning functions and benefits can only provide temporary relief and can be detrimental over a long period. The horizontal shearing or abrupt density change caused between tilled topsoil and the subsurface soil can create a hardpan below the tilled zone affecting root growth and water infiltration. Exposure of the topsoil due to lack of surface residue cover can lead to soil erosion by water and wind, which can cause nutrient losses and pollution. The continuously tilled soil can lose its aggregate structure and eventually be prone to reduced air and water movement, root growth, and crop yields. The crop residues require oxygen for decomposition, and a moldboard plow buries them to 9 inches below the surface, which can cause them to be unexposed to oxygen, leading to slow/no decomposition. Even though the soil water movement can increase over the short term, soil crusting occurs after multiple rainfall events that hinder water infiltration. The energy requirement is the highest per unit field area for moldboard plowing among all the tillage practices. Another major disadvantage associated is the need for subsequent secondary tillage operations requiring multiple passes over the field.

A general-purpose moldboard plow has parts like share, shin, moldboard, landside, frog, and brackets. The share has a pointed end which cuts through the soil allowing the plow to run through the ground. The furrow bottom is cut by share, and the furrow wall is created by shin. The landside runs along the furrow wall and is parallel to the share. The frog is an iron piece that holds share, shin, and landside together and is attached to the beam via standard with one or more braces. Various versions of moldboard bottom, like sod bottom and stubble bottom, can be used based on soil conditions. In addition, moldboard plows can have rolling landside, coulters, and jointers. The rolling landside helps with the adjustment of pressure on the furrow wall; rolling coulters facilitate the cutting of heavy sod and residue; and jointers help move the trash (residue, sod, manure) from the edge of the furrow slice into the bottom for enhanced coverage.

Even though, there are temporary benefits, conventional tillage practices like moldboard plowing have been shown to cause detrimental impacts on soil quality and crop productivity in the long run: increase in greenhouse gas emissions, lower soil organic matter, disrupted soil structure, reduced water infiltration and enhanced soil erosion. In addition, the reduction in the number of passes across the field, the lower energy requirements, less time, and less labor are other factors that can motivate farmers towards a conservation management system, including cover crops and minimal tillage practices. However, the moldboard plow/conventional tillage can still be recommended in certain situations, like while converting a fallow land into production or in areas with cool and humid weather, where the need for enhanced soil drainage and spring warming outweighs the disadvantages. Therefore, the decision for tillage and the choice of method can be taken based on your soil conditions and particular requirements while keeping in mind the need for sustainable farming. Those interested in learning further about the various tillage practices can visit the extension website portal and join our extension and education activities.

Please check for a factsheet comparing conventional and conservation tillage practices.

Long-Term Tillage Effects on Corn and Soybean Yield in the Piedmont