Ronald D. Morse

A conservation-tillage, cover-cropping strategy and economic analysis for creamer potato production

A two-year experiment was conducted at the Beltsville Agricultural Research Center (BARC), MD, and Virginia Polytechnic Institute and State University Kentland Agricultural Research Farm (KARF), VA, to evaluate potato (Solanum tuberosum L.) production of 32- to 57-mm-size-range tubers (referred to hereafter as creamers) in a conservation-tillage, cover-cropping strategy. The experiments used a split-plot design in which the main-plots were cover crop treatments and the sub-plots were different potato selections. Main plot treatments included rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), Austrian winter pea (Pisum sativum L.), rape (Brassica napus L.), oat (Avena sativa L.), rye/crimson clover mixture, rape/crimson clover mixture, bare soil/raised beds, and bare soil/flat beds (control). Potato selections tested were B1145-2, B1491-5, and B1492-12 in 2000 and B1145-2, B1102-3, and B0811-4 in 2001. Yields in the conservation-tillage treatments were equal to or better than those in the bare soil/flat bed control with few exceptions. Large-sized tubers (<57 mm) in almost all cases remained below 6% of total marketable yield even when the tubers were harvested late. Delayed harvest did not reduce creamer-sized yields nor did it increase yield of large-sized tubers. Economic analysis shows that net returns from some conservation-tillage treatments are equal to or higher than the conventional-tillage strategy and confirms the viability of the conservation-tillage, cover-cropping strategy. Furthermore, the conservation-tillage strategy in many cases allows timely planting using machinery in the wet soils of Maryland and Virginia during the narrow window of spring potato planting time, whereas the conventional tillage strategy does not offer this advantage.ResumenUn experimento de dos años de duración fue realizado por el Centro de Investigación Agrícola de Beltsville (BARC), MD y el Instituto Politécnico de Virginia en la Granja de Investigación Agrícola Kentland de la Universidad del Estado (KARF), VA, para evaluar la producción de tubérculos de papa (Solanum tuberosum L.) de 32 a 57mm de tamaño (referidos en lo sucesivo como “creamers”)) con estrategia de labranza de conservación, cultivo de cobertura. Los experimentos se hicieron empleando el diseño experimental de parcelas divididas, en el cual las parcelas principales fueron con tratamiento de cultivos de cobertura y las subparcelas fueron diferentes selecciones de papa. Los tratamientos de las parcelas principales incluyeron centeno (Secale cereale L.), trébol rojo (Trifolium incarnatum L.), guisante austriaco de invierno (Pisum sativum L.), colza (Brassica napus L.), avena (Avena sativa L.), mezclas de centeno/trébol rojo, colza/trébol rojo, suelo sin labranza/camas altas y suelo sin labranza/camas a nivel (testigo). Las subparcelas incluyeron las selecciones de papa B1145-2, B1491-5 y B1492-12 en el 2000 y B1145-2, B1102-3 y B0811-4 en el 2001. Los rendimientos de los tratamientos de labranza de conservación fueron iguales o mejores, con pocas excepciones, que los de los controles sin labranza / camas a nivel. Los tubérculos de tamaño grande (<57mm) en casi todos los casos estuvieron por debajo del 6% de rendimiento total comerciable aun cuando se cosecharon un tiempo después. La cosecha diferida no redujo los rendimientos de los tubérculos del tamaño “creamer” ni tampoco se incrementó el rendimiento de tubérculos de mayor tamaño. El análisis económico muestra que las ganancias netas de algunos de los tratamientos con labranza de conservación, son iguales o mayores que los de la estrategia de labranza convencional y confirman la viabilidad de la estrategia de labranza convencional, cultivos de cobertura. Más aun, la estrategia de labranza de conservación permite, en muchos casos, la siembra a tiempo, utilizando maquinaria en suelos húmedos de MD y VA, durante la corta temporada de siembra de papa de primavera, mientras que la estrategia de labranza convencional no ofrece esta ventaja.

Delayed inoculation and starter nitrogen for enhancing early growth and nitrogen status ofLespedeza cuneata

SummaryTwo growth chamber experiments were conducted to determine the response ofLespedeza cuneata (Dumont) G. Don. (sericea lespedeza) to delayed inoculation and low levels of nitrogen fertilization. Nitrogen was supplied either as NH4+ or as NO3− in solution. At 0.5 and 5.0 ppm nitrogen early growth and N2(C2H2) fixation was inhibited by NH4+ and promoted by NO3−. Inoculation at seeding did not negatively affect growth prior to the onset of N2(C2H2) fixation. Delayed inoculation until the trifoliate stage thus did not increase growth or N2 fixation during the first 40 days of growth. After 40 days, specific nitrogenase activity was highest for plants inoculated at the first trifoliate stage of growth. In contrast, growth and total shoot nitrogen accumulation were higher in plants inoculated at planting. The experimental results suggest that delaying inoculation is not a useful technique for improving early growth ofL. cuneata for surface mine reclamation.

Organic broccoli production on transition soils: comparing cover crops, tillage and sidedress N.

Little information is available about how farmers in transition to organic practices should manage short- and long-term N fertility. The objectives of this research were (1) to evaluate the leguminous cover crops lablab ( Dolichos lablab L.), soybean ( Glycine max L.), sunn hemp ( Crotalaria juncea L.) and a mixture of sunn hemp and cowpea ( Vigna sinensis Endl.) as N sources; (2) to compare N availability and broccoli yield when cover crops were incorporated with conventional tillage (CT) or retained as a surface mulch using no-tillage (NT) practices; and (3) to quantify the amount of supplemental sidedress nitrogen required to maximize the yield of organic broccoli ( Brassica oleracea Group Italica) on transition soils. Broccoli was grown during the first year after organic transition in the spring and fall of 2006 at the Kentland Agricultural Research Farm near Blacksburg, VA. Spring ( P P −1 , and showed a quadratic correlation with leaf N ( P = R 2 =0.80 and P = R 2 =0.38, respectively). There was no difference in spring broccoli yield between CT and NT; however, CT produced the highest yield in the fall crop. At low sidedress N rates, leaf N was highest in CT plots, but tillage had no effect on N uptake at high N rates. This indicates that early season and perhaps total plant-available mineralized N was greater in CT than NT; however, potential N deficiency in NT soil may be compensated by sidedress N. Broccoli yield was not affected by leguminous cover crop, even though the quantity of cover crop biomass and N contribution was different among species. This suggests that N availability from leguminous cover crops may be impacted by other ecological processes such as soil microbial activity. This study shows that organic CT and NT growers can maximize broccoli yield in transition soils low in N availability, by using leguminous cover crops in combination with moderate amounts of sidedress N.

Field evaluation of starter N and delayed inoculation ofLespedeza cuneata grown in minesoil

A field study was conducted on freshly reclaimed surface-mined area to determine response of sericea lespedeza (Lespedeza cuneata [Dumont] G. Don.) to delayed rhizobial inoculation. Soybeans (Glycine max L.) were used as a control legume. Plots were inoculated with spray applications of rhizobial suspensions at seeding, cotyledon stage or second trifoliate leaf stage, or not inoculated. Starter N at 0, 10 or 20 kg ha−1 was applied preplant in a factorial arrangement with inoculation timings.G. max. was grown for 92 days andL. cuneata for 121 days.Starter N increased plant growth and total shoot N in both species. However, % shoot N was found to increase only inL. cuneata. Delaying inoculation had no significant effect upon total shoot N or % shoot N accumulation inL. cuneata. Inoculation ofG. max at planting produced greater plant growth and N accumulation than delayed inoculation treatments. Application of inoculum as a surface spray appeared to be an effective method for delayed inoculation as evidenced by nodule formation. Lack of increased plant growth, regardless of time of inoculation, suggests that delayed inoculation does not improve establishment and growth ofL. cuneata in minesoil.

Evaluation of rhizobial strains nodulating lespedeza cuneata for improving n input into minesoil revegetation systems

Abstract This study was designed to identify strains of Bradyrhizobium sp. (lespedeza) which could improve the plant performance and N status of Lespedeza cuneata (Dumont) G. Don (sericea lespedeza). Based upon preliminary screening for nodulation capability and acetylene reducing activity (ARA), six strains of rhizobia were chosen to be evaluated in the greenhouse for plant growth effects and N2‐fixing ability. The L. cuneata symbiosis with two strains, VPI 142 and VPI 163, resulted in the greatest plant growth, total N accumulation, and highest nodule nitrogenase activity (acetylene reduction activity). The high correlation (significant at the 1% level) of shoot dry weight with root dry weight (r = .94), nodule dry weight (r = .92), total shoot N (r = .98), total root N (r = .92), as related to nitrogenase activity of the nodule mass (r = .71), indicates that plant dry weight could be used as an easily determined measurement for screening isolates to be used with L. cuneata. The identification of effici...

The effect of delayed inoculation on nitrogen fixation by Phaseolus vulgaris L. Grown in minesoil

Abstract The influence of delayed inoculation on N2(C2H2)‐fixation by Phaseolus vulgaris L. grown in minesoil is described. Fertilizer treatments included in the study were 0, 25, 50, and 100 kg N/ha applied at 21 days or at seeding. A peat culture of Rhizobium phaseoli was inoculated at 21 days or at seeding. Nitrogenase activity was determined by reduction of C2H2 to C2H4, at 7, 21, 35, and 49 days. Nitrogenase activity was related to N‐fertilizer rate and treatment sequence. Addition of 25 kg N/ha significantly stimulated N2(C2H2)‐ fixation while greater rates of N‐fertilizer decreased the rate of Ng(C2H2)‐fixation. The results of this study suggest that addition of 25 kg N/ha at time of seeding, followed by inoculation with R. phaseoli after legume growth has been established (21 days) results in an initial greater amount of N2(C2H2)‐fixation.

Nodulation and nitrogen fixation of Phaseolus vulgaris L. grown in minesoil as affected by soil compaction and N fertilization

Abstract The objectives of this growth chamber study were to assess the influence of three soil compaction levels, as determined by bulk density, and four N fertilizer treatments on growth, nodulation and N2 fixation of P. vulgaris in minesoils. Shoot and root growth was severely retarded and nodulation essentially absent in N unfertilized, uninoculated (control) plants. With inoculated plants, root and shoot mass increased and nodule mass decreased as bulk density was decreased from 1.55 g/cm3 (unamended) to 1.40 g/cm3 (amended with 50% by volume sand). Root and shoot mass increased as N fertilizer rates increased from 0 to 100 kg N/ha. Nodule mass increased at 25 kg N/ha, but higher N rates decreased nodule mass compared to unfertilized plants. There was no significant correlation between bulk density and N2 fixation, as measured by the acetylene reduction assay. In general, N2(C2H2) fixation was the greatest at 35 days from seeding; however, at 21 days, unfertilized plants showed high N2(C2H2) fixation...