International audienceThe ‘4 per mille Soils for Food Security and Climate’ was launched at the COP21 with an aspiration to increase global soil organic matter stocks by 4 per 1000 (or 0.4 %) per year as a compensation for the global emissions of greenhouse gases by anthropogenic sources. This paper surveyed the soil organic carbon (SOC) stock estimates and sequestration potentials from 20 regions in the world (New Zealand, Chile, South Africa, Australia, Tanzania, Indonesia, Kenya, Nigeria, India, China Taiwan, South Korea, China Mainland, United States of America, France, Canada, Belgium, England & Wales, Ireland, Scotland, and Russia). We asked whether the 4 per mille initiative is feasible for the region. The outcomes highlight region specific efforts and scopes for soil carbon sequestration. Reported soil C sequestration rates globally show that under best management practices, 4 per mille or even higher sequestration rates can be accomplished. High C sequestration rates (up to 10 per mille) can be achieved for soils with low initial SOC stock (topsoil less than 30 t C ha−1), and at the first twenty years after implementation of best management practices. In addition, areas which have reached equilibrium will not be able to further increase their sequestration. We found that most studies on SOC sequestration only consider topsoil (up to 0.3 m depth), as it is considered to be most affected by management techniques. The 4 per mille number was based on a blanket calculation of the whole global soil profile C stock, however the potential to increase SOC is mostly on managed agricultural lands. If we consider 4 per mille in the top 1m of global agricultural soils, SOC sequestration is between 2-3 Gt C year−1, which effectively offset 20–35% of global anthropogenic greenhouse gas emissions. As a strategy for climate change mitigation, soil carbon sequestration buys time over the next ten to twenty years while other effective sequestration and low carbon technologies become viable. The challenge for cropping farmers is to find disruptive technologies that will further improve soil condition and deliver increased soil carbon. Progress in 4 per mille requires collaboration and communication between scientists, farmers, policy makers, and marketeers
Spring N applications increase wheat (Triticum aestivum L.) grain yields in the Mid‐South. The interactive effect of increased N rates and foliar fungicide applications on the common Mid‐South winter wheat foliar diseases—leaf blotch (Septoria tritici Rob. in Desm.), glume blotch and leaf spot [S. nodorum (Berk.) Berk.], and leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici)—is not clearly understood. Research was initiated in 1984 on a Collins silt loam soil (coarse‐silty, mixed, acid, thermic Aquic Udifluvents) and continued each year through 1987 to evaluate the effect of N rates and fungicide applications on disease severity in wheat. Spring N rates of 0, 30, 45, 60, 90, and 120 lb/acre were applied at Feekes' growth stage (GS) 3. Fungicides were applied twice during the spring at GS 8 to 9 and GS 10.1 to 10.5. The research was continued between 1988 and 1990 on a Loring silt loam soil (fine‐silty, mixed, thermic Typic Fragiudalfs), but with a reduced number of N treatments. Experimental sites were changed each year on these two soils. The effects of N rates and fungicide applications to wheat were evaluated through grain yields, kernel weights, test weights, and estimated percentage plant foliage and heads infected by diseases. The applied N rates did not have the same effect on increasing yields during the years of the experiment. Generally, yields were increased to a level and then decreased with higher N rates. Fungicide applications had a greater effect on yields produced at the higher N rates. Severity of diseases differed with year, N rate, and fungicides. The severity of the three diseases was increased with N rate, especially when fungicides were not applied, but fungicides reduced disease severity. Yield reductions could not be attributed to any single disease but to a combination of diseases, and reductions could not be ascertained from kernel weights or test weights. Research Question Throughout the Mid‐South, wheat yields may be reduced by one or more plant diseases that may incraese with incraesed N fertilization. This study evaluates spring N and foliar fungicide effects on grain components and disease severity of wheat. Literature Summary Diseases have had a negative but inconsistent effect on grain yields. Not only is severity inconsistent with years, but the predominate disease may differ. In this region, one or more diseases may affect wheat during the growing season. High N rates tend to increase infection by increasing plant susceptibility to these diseases. The disease severity increases with applied N when fungicides are not applied. Study Description Spring N rates and fungicides were applied over 7 yr, evaluating their effect on wheat. Experiment Design: Main‐plots, spring N rates of 0, 30, 45, 60, 90, and 120 lb/acre plus a split N rate (45 lb applied at Feekes’ GS 3 + 45 lb applied 3 to 4 wk later) were applied to a Collins silt loam soil for 1984 through 1987. Main plot N rates plus the split‐rate were applied to a Loring silt loam soil. Sub‐plots, fungicides, Bayleton p...
Rothrock, C. S., Winters, S. A., Miller, P K., Gbur, E., Verhalen, L. M.,
Rotations have long been used to improve crop yields. No‐tillage production acreage is increasing, and production information on rotation effects on yields and soybean cyst nematode populations is needed for this system. Field experiments were initiated in 1985 and continued through 1992 to evaluate P‐K fertilization effects on yield of a corn‐soybean [Zea mays L.‐Glycine max (L.) Merr.] rotation and on populations of soybean cyst nematode (Heterodera glycines Ichinohe) (SCN). The research was conducted on a Loring silt loam soil (a fine‐silty, mixed, active, thermic Oxyaquic Fragiudalf), using no‐tillage management. The experimental design was a split‐plot for corn evaluation and split‐split‐plot for soybean evaluation. Individual treatments were replicated five times. Main plots were broadcast P‐K rates of 0–0, 15–28, 29–56, 44–84, and 59–112 kg ha−1. The split‐plots were continuous corn, continuous soybean, a corn‐soybean rotation, and a soybean‐corn rotation. The split‐split‐plots were two soybean cultivars possessing different levels of SCN resistance. Yields of both crops were increased by the fertilization. In this study, corn yields were increased 14% and soybean yields increased 11% with the rotation. Rotating the two cultivars produced similar yields and nonrotated yields of resistant TN 4‐86 were higher than susceptible Essex, indicating an effect of SCN. The primary benefit of corn in the rotation was to reduce SCN populations. However, within Essex rotations the SCN population recovery was rapid, while populations remained relatively low in the TN 4‐86 rotations. The SCN populations were greater when rotations were fertilized with the two lowest P‐K rates, compared with populations within the unfertilized check and the highest P‐K rate. Soybean producers should consider a no‐tillage system of rotating corn with SCN‐resistant soybean cultivars, fertilized at high P and K rates for yield improvement and reduced SCN populations.
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