Soil Fertility Values Research Articles

Soil fertility and slope processes in the Western Cumberland Escarpment of Kentucky: influences on the development of horticulture in the Eastern Woodlands

The archaeological record of dry rockshelters in the Red River Valley of eastern Kentucky contains botanical remains of several weedy annual seed-bearing plants that point to the independent development of agriculture during the Late Archaic and Early Woodland Period. The objective of this study is to gather quantitative data through the chemical and physical analysis of soils collected within a valley transect to gain insights into landscape processes and soil fertility that may have played a role in the early development of plant domestication and the location of garden plots in relation to rock shelter sites in the upper Cumberland Plateau region of eastern Kentucky. Soils on upland benches formed in limestones have soil fertility values that are comparable to fertile floodplain soils. Upslope outcrops of calcareous bedrock are contributing basic cations to these bench soils. Additionally, in comparison to other landscape positions these upland soils have high levels of organic carbon, available P and greater C:N ratios. Soil morphology, radiocarbon dates, and archaeological evidence indicate that many of the numerous earthflows and debris flows within the region are Early to Middle Holocene in age. These slides were likely generated by Mid-Holocene climatic shifts in which the frequency and intensity of summer precipitation increased across the southeastern United States. These slope failures may have contributed to the development of plant domestication by creating forest canopy gaps and disturbed soils in which weedy plants thrived.

Agroecosystem Performance during Transition to Certified Organic Grain Production

The 2002 U.S. Farm Bill offers incentives to support the transition from conventional to certified organic production. Research‐based recommendations must be developed for suitable crop rotations that provide high yields, grain quality, and adequate soil fertility during the transition. We compared replicated conventional and organic systems, using identical crop varieties, during the 3‐yr transition period and the fourth year following a full rotation of organic corn (Zea mays L.)–soybean [Glycine max (L.) Merr.]–oat (Avena sativa L.)–alfalfa (Medicago sativa L.) to determine which rotation was associated with the lowest risk during transition. Organic feed corn yields at the Neely–Kinyon long‐term agroecological research (LTAR) site in Greenfield, IA, were equivalent to conventional yields in the transition years, and in the fourth year, the organic corn yield of 8.1 Mg ha−1 in the longest rotation was greater than the conventional corn yield of 7.1 Mg ha−1 in the conventional corn–soybean rotation. Organic and conventional soybean yields were similar in the 3 yr of transition. Organic soybean yield of 3.0 Mg ha−1 exceeded the conventional yield of 2.7 Mg ha−1 in the fourth year of organic production. Pre‐ and postharvest soil fertility values were responsive to manure application, but few differences between systems were observed. Grass and broadleaf weed populations varied between the organic and conventional systems each year, but the impact on yield was considered negligible. Corn borer (Ostrinia nubilalis) and bean leaf beetle (Ceratoma trifurcata) populations were similar between systems, with no effect on yield. We conclude that organic grain crops can be successfully produced in the 3 yr of transition to organic, and additional economic benefits can be derived from expanded crop rotations.

Relationships between soil bulk electrical conductivity and the principal component analysis of topography and soil fertility values

Measures of soil electrical conductivity (EC) and elevation are relatively inexpensive to collect and result in dense data sets which allow for mapping with limited interpolation. Conversely, soil fertility information is expensive to collect so that relatively few samples are taken and mapping requires extensive interpolation with large estimation errors, resulting in limited usefulness for site-specific applications in precision agriculture. Principal component (PC) analysis and cokriging can be applied to create meaningful field scale summaries of groups of attributes and to decrease the estimation error of maps of the summarized attributes. Deep (0–90 cm) and shallow (0–30 cm) EC, elevation, and soil fertility attributes were measured in fields under corn (Zea mays L.) and soybean (Glycine max L.) rotations, at two sites in Illinois (IL) and two sites in Missouri (MO). Soil fertility and topography attributes were summarized by PC analysis. The first topography PC (TopoPC1) contrasted flow accumulation against elevation and curvature, to describe the main topographic pattern of the fields. The first soil fertility PC (SoilPC1) consistently grouped together cation exchange capacity (CEC), Ca, Mg, and organic matter (OM). SoilPC1 was well correlated to soil EC for all sites and cokriging with EC had higher r 2 in the crossvariogram models compared to ordinary kriging. The second and third soil fertility PCs (SoilPC2 and SoilPC3) were concerned with soil pH and P, and reflected historic land use patterns. Maps of SoilPC2 and SoilPC3 had little relationship to soil EC or topography and so could not be improved by cokriging. Abbreviations: CEC – cation exchange capacity; EC – soil bulk electrical conductivity; OM – soil organic matter; PC – principal component; SoilPC – soil fertility principal component; Sph – spherical variogram function; TopoPC – topography principal component.

Variable rate fertilizer application for corn and soybean

Some have argued that variable rate application (VRT) of fertilizer is appropriate and profitable for the highly productive and fertile fields of the central cornbelt, but the proposition has not been tested. In this field experiment treatments of variably and uniformly applied phosphorus (P) and potassium (K) fertilizer and a control treatment with no P or K fertilizer were applied in a randomized complete block design at six locations in central Illinois in 1994. Individual experimental units were from 1,000 to 1,500 m in length and about 20 m in width. Fertilizer application rate was based upon a 100 m grid soil sampling. The variable rate treatment rate for each plot was based upon interpolated values of the soil fertility of each portion of the experimental unit. Uniform rate treatments were based upon the median soil fertility value for the entire field. Yield estimates were obtained with grain yield monitors. Neither corn nor soybean yield was significantly affected by fertilizer application treatment. We propose this lack of an effect is due to insurance built into the current fertility recommendations. A response to variable treatments will not be seen if there is no response to fertilization. Variable rate application will probably be most useful in fields with areas of very low soil tests.

The effect of sampling depth and thatch on soil test results of turfgrass areas

Abstract The effects of sampling depth and thatch on soil test results of turfgrass areas were studied. Several turfgrass areas with known fertility and management histories were sampled in 3.8 or 5.0 cm increments to depths of 10 or 15 cm. Sampling depth significantly affected the levels of P, K, Mg, Ca, and pH in one or more of the areas sampled. The direction and magnitude of change was dependent on such factors as previous rates of fertilization, soil texture, and various management practices. Although soil fertility values changed with depth, changes in fertilizer recommendations due to sampling depth were minimal. Sampling depth data also gave an indication of greater nutrient removal in the surface 4 to 5 cm of soil than at lower depths. The inclusion of thatch with the soil sample increased soil test levels of K and CEC, decreased pH, and did not affect P levels.