Raymond N. Gallaher

Soil penetrometer resistance and bulk density relationships after long‐term no tillage

Abstract Soil penetrometer resistance (SPR) and bulk density (p) measurements can be used for assessing soil strength or density. Results from this research add to the understanding of residual soil compaction of sandy soils by answering three questions: What are the long term effects of no‐tillage on SPR and p in a double‐cropping rotation? Where in the soil profile are maximum SPR and p values found? How much of the variations in SPR are accounted for by the regression of p? Compaction was evaluated at the end of an 8‐yr oat (Avena sativa L.)/Bragg soybean [Glycine max (L.) Merr.] double‐cropping tillage experiment. The soil was Arredondo fine sand (Grossarenic Paleudults). The four treatments (replicated four times) included no‐tillage (NT), conventional tillage (CT), no‐tillage plus in‐row subsoiling (NTPS), and conventional tillage plus in‐row subsoiling (CTPS). Forty days after planting soybeans the soil was irrigated to field capacity. Readings were taken to a depth of 60 cm at five positions in th...

Cover crops and organic mulches for nematode, weed and plant health management

Summary – Traditional cover cropping systems for nematode management seldom consider weed and soil nutrient management concurrently. Integrating cover crops suppressive to plant-parasitic nematodes with a cover crop mulching system could improve traditional approaches. Two field experiments were conducted in 2003 and 2004 to evaluate ‘Tropic Sun’ sunn hemp (Crotalaria juncea) and ‘Iron Clay’ cowpea (Vigna unguiculata) as summer cover crops and as organic mulches. Both experiments were in a 3 × 3 split-plot design in which the main plots were summer planting of sunn hemp, cowpea or fallow, and the subplots were organic mulch of sunn hemp, cowpea or no mulch. The summer cover crop was followed by turnip (Brassica rapa) and lima bean (Phaseolus lunatus )i n the autumn. Using sunn hemp as organic mulch suppressed root-knot nematodes more effectively than using it as a cover crop, but only on a less susceptible host such as turnip, and not on a very susceptible host such as lima bean. While sunn hemp as a cover crop failed to enhance beneficial free-living nematodes, sunn hemp as an organic mulch enhanced bacterial-feeding nematode population densities. Sunn hemp mulch also suppressed broadleaf weeds but not grasses or nutsedges. Although sunn hemp and cowpea cover crops did not increase lima bean N and K content, their mulches increased N and K content. Similar results were observed for turnip and lima bean yields. Population density of root-knot nematodes was positively related to abundance of omnivorous nematode in 2003. The abundance of plant-parasitic nematodes was negatively related to the infestation levels of Pasteuria penetrans, and the abundance of predatory nematodes in 2004. Factors that might have affected the performance of sunn hemp on nematode communities are discussed.

Effect of no‐tillage vs. conventional tillage on soil organic matter and nitrogen contents 1

Abstract Four treatments (no‐tillage plus subsoiling, no‐tillage, conventional tillage plus subsoiling, and conventional tillage) were continuously in place for 6 yr and a second set of no‐tillage plus subsoiling and conventional plus subsoiling treatments were continuously in place for 3 yr to study the long‐term effects of conventional and no‐tillage corn on soil organic matter (OM) and N contents. Soil samples were taken at random between the rows and in the rows to a depth of 60 cm, in 5‐cm increments to a depth of 30 cm, and then in 15‐cm increments from the 30 to 60‐cm depth for OM and N determination. No‐tillage resulted in A3 and 20% more Kjeldahl N than conventional tillage in the 0 to 5‐cm soil depth after 6 and 3 yr, respectively. after 6 yr, the 0 to 5‐cm depth had 36% more OM in no‐tillage treatments than in conventional tillage treatments, and soil from no‐tillage treatments averaged 27% more OM than the conventional tillage plus subsoiling treatment at the 0 to 15‐cm soil depth.

Some factors influencing yield and cation sum and ratios in corn 1

Abstract Maximum yields of corn depends on adequate and balanced supplies of essential nutrients. In order to elucidate some of the factors which influence yields, a study was initiated to evaluate K, Ca, and Mg balances as influenced by seasonal variation, age of plants, and rates of K application. Corn was grown three consecutive years on a Hartsells loam at three levels of applied K. Significant yield response to applied K was observed. The level of response to K was dependent upon weather conditions. Fertilizer K, age, and yearly variation resulted in significant changes in the sum of the cations (K+Ca+Mg), and the K/Ca, K/Mg, and K/(Ca+Mg) ratios in corn leaf tissue. Grain yield and K concentration in corn tissue increased while the tissue concentration of Ca and Mg decreased as a result of K application.

Soil nutrient and plant responses to solarization in an agroecosystem utilizing an organic nutrient source

Soil solarization is used to manage nematodes, pathogens and weeds, but relatively few studies have examined solarization effects on soil mineral nutrients, soil properties and plant tissue nutrients. This study was designed to optimize the duration of solarization treatment for the management of soil and plant nutrients and crop biomass in an agroecosystem utilizing an organic nutrient source. The experiment was a split-plot with treatment duration as the main effect and solarization as the sub-effect. Solarization treatments of 2-, 4- and 6-week durations began on sequential dates and concluded in mid-August. Immediately post-treatment, okra ( Hibiscus esculentus L.) seedlings were transplanted into subplots for tissue nutrient analysis. Freshly chopped cowpea [ Vigna unguiculata (L.) Walp.] hay was applied to the soil surface directly around the okra seedlings as an organic nutrient source. Immediately following solarization treatment, concentrations of soil K and Mn were higher, while Cu and Zn concentrations were lower in solarized soils than in non-solarized soils. Soil pH was slightly lower in solarized plots. Concentrations of K, N, Mg and Mn in okra leaf tissue were higher in solarized plots than in non-solarized plots, but concentrations of P and Zn were lower in plants grown in solarized soil. Okra biomass was three and four times higher in the 4- and 6-week solarization treatments than in non-solarized treatments. Based on data from this experiment, 4- and 6-week durations of solarization were optimal for increasing crop biomass. The data indicate that solarization has significant effects on soil and plant nutrients. Results of the nutrient analyses suggest that the availability of nutrients from an organic source was not limited by solarization.

Leaf magnesium concentration efficiency versus yield efficiency of corn hybrids

Abstract Soils low in Mg are common in the humid high rainfall areas of the world. Magnesium deficiency is frequently observed in corn (Zea mays L.) grown on the highly weathered soils of the Southeastern United States. This study reports on the effectiveness of Mg fertilizer to correct a Mg deficiency in young growing corn hybrids, to evaluate commercial corn hybrids for their Mg uptake efficiency as measured by ear leaf analysis, and to compare leaf Mg efficiency with yield efficiency. Paired rows of 28 hybrids on irrigated and nonirrigated plots were compared for their elemental ear leaf composition and yield following treatment of sidedress application of MgSO4.7H2O when corn was about 60 cm tall. Fertilizer Mg did not influence yield on either plots nor did it influence Mg and other cation concentrations in the ear leaf in the nonirrigated plots. The applied Mg fertilizer did influence the Mg concentration in the ear leaf and caused significant interactions with other cations in the hybrids on the ir...

Response of lima bean to inorganic nitrogen and broiler manure sources and rates

Abstract Applying animal manure to crops is a good disposal practice that also recycles nutrients. A 2‐year study was conducted involving lima bean (Phaseolus lunatus L.) and two N sources, ammonium nitrate (AN, 340 g N kg−1), and broiler chicken manure (BM, 10 g N kg−1). The sources were tested at five N rates (0, 67, 135, 202, and 269 kg N ha−1) in a split‐plot design with N source as the main plot and N rate as the subplot. Treatments were replicated three times in 2000 and four times in 2001. Leaf tissue (early flowering stage) was analyzed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn). Although most nutrients were within or above the sufficiency range, K and Cu limited crop production for all treatments. There was no difference between N sources for fresh pod yields. The highest fresh pod yield occurred at 213 kg N ha−1, but the critical point was obtained with 100 kg N ha−1, a rate agreeing with current University of Florida recommendations.