Reducing Tillage Affects Long-Term Yields but Not Grain Quality of Maize, Soybeans, Oats, and Wheat Produced in Three Contrasting Farming Systems

Abstract

Reducing tillage has been widely promoted to reduce soil erosion, maintain soil health, and sustain long-term food production. The effects of reducing tillage on crop nutritional quality in organic and conventional systems, however, has not been widely explored. One possible driver of crop nutritional quality might be the changing soil nitrogen (N) availability associated with reduced tillage in various management systems. To test how reducing tillage affects crop nutritional quality under contrasting conventional and organic farming systems with varied N inputs, we measured nutritional quality (protein, fat, starch, ash, net energy, total digestible nutrients, and concentrations of Ca, K, Mg, P, and S) of maize, wheat, oats, and soybeans harvested from a long-term trial comprised of three farming systems under two tillage regimes: a conventional grain system (CNV); a low-input organic grain system (LEG); and an organic, manure-based grain + forage system (MNR) under conventional full-tillage (FT) and reduced-till (RT) management. Although maize and wheat yields were 10–13% lower under RT management, grain quality metrics including protein, fat, starch, energy, and mineral concentrations were not significantly affected by reducing tillage. Differences in nutrient quality were more marked between farming systems: protein levels in maize were highest in the MNR system (8.1%); protein levels in soybeans were highest in the LEG system (40.4%); levels of protein (12.9%), ash (2.0%), and sulfur (1430 ppm) in wheat were highest in the CNV system, and oat quality was largely consistent between the LEG and MNR systems. As grain quality did not significantly respond to reducing tillage, other management decisions that affect nutrient availability appear to have a greater effect on nutrient quality.

Effects of Different Tillage and Residue Retention Measures on Silage Maize Yield and Quality and Soil Phosphorus in Karst Areas

“…This study found that no-tillage conditions significantly increased the crude protein content of maize, whereas the addition of cover crop measures balanced the negative impact of conventional tillage on crude protein content. Clearly, not tilling has a positive effect on soil nutrients and enhances maize's utilization of nitrogen [8]; however, the contribution of legume cover crops on soil nitrogen cannot be ignored [19]. The present study also found that cover crops significantly increase the crude fat content of silage maize and that the combination of no tillage and cover crops also enhances it (although not significantly); moreover, there is a significant positive correlation between crude fat and MBP.…”

“…The dried samples were pulverized with a plant powder sampler and sealed through a 0.35 mm sieve for storage. The samples were used for the determination of crude fiber (CF), crude ash (Ash), and crude fat according to Pearsons et al [19] and total nitrogen (TN), neutral detergent fiber (NDF), and acid detergent fiber (ADF) content via Kjeldahl nitrogen determination, the salicylic acid colorimetric method, the indotrione colorimetric method, and Van's cellulose content determination method [20,21].…”

Reducing tillage does not affect the long-term profitability of organic or conventional field crop systems

“…Compared to the RT organic systems, this left an additional 2 months without living cover-a higher risk for erosion, nutrient loss, and missed opportunities to build soil health (Dabney et al, 2001). The LEG system, despite supporting continuous living cover for over 10 months of the year, did not support robust crop growth and high yields (Pearsons et al, 2022). The low-input design of the LEG system did help minimize fertility costs, but such low inputs significantly limited crop productivity.…”

“…Student's t-tests were used to test if average crop yields were significantly different than county averages (H 0 : Y R = 1) for each crop in each treatment. Raw yield data from the FST for this period (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020) were analyzed and discussed as part of an assessment of grain quality from the FST (Pearsons et al, 2022).…”

“…Pairwise mean comparisons were generated using the EMMEANS function from the "emmeans" package, with "mvt" P-value adjustments to account for multiple comparisons (Lenth, 2021). Raw yield data from the same period (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020) for this experiment have been previously analyzed and discussed as part of an assessment of grain quality from the FST (Pearsons et al, 2022).…”