Ray D. William

Effect of No-Till or Conventional Planting and Cover Crops Residues on Weed Emergence in Vegetable Row Crop1

The effect of planting system and cover crop residues on weed emergence in irrigated vegetable row crops was studied in field experiments from 1995 through 1997. Vegetable crops were either no-till planted (NTP) through cover crop residues or conventionally planted (CP) into soil with cover crop residues incorporated. NTP reduced emergence of hairy nightshade by 77 to 99% and Powell amaranth emergence by 50 to 87% compared with CP. Cover crop treatments were much less important than planting system in regulating weed emergence. Tillage in the spring did not increase the number of viable seeds near the soil surface. Hairy nightshade emergence ranged from 0.6 to 9.8% of the intact seeds in CP compared with 0 to 0.1% emergence of the seeds in the NTP plots. Powell amaranth emergence ranged from 4.9 to 6.5% of the intact seeds in CP contrasted with only 0.4 to 0.9% emergence of the seeds in NTP plots. Nomenclature: Hairy nightshade, Solanum sarrachoides Sendtner #3 SOLSA; Powell amaranth, Amaranthus powellii S. Wats # AMAPO. Additional index words: Conventional tillage, cover crops, no till, no-till planting, primary tillage, weed emergence, weed seedbank. Abbreviations: CP, conventionally planted; NT, no till; NTP, no-till planted; WAP, weeks after planting.

Effect of cover crops and tillage system on symphylan (Symphlya: Scutigerella immaculata, Newport) and Pergamasus quisquiliarum Canestrini (Acari: Mesostigmata) populations, and other soil organisms in agricultural soils

Abstract The garden symphylan ( Scutigerella immaculata : Newport) is a common myriapod soil pest of vegetable crops in the Pacific Northwest and other regions of the US. Symphylans consume germinating seeds, plant roots, and above-ground plant parts in contact with the soil. Factors regulating symphylan populations in agricultural soil systems are poorly understood, particularly the effects of farming practices such as cover cropping and reduced-tillage. Cover crops were planted in the fall of 1994 through 1996 and either incorporated into the soil in the spring with tillage or killed with glyphosate and the residue left on the soil surface. Fewer symphylans were recovered with Berlese funnels from soil under cereal cover crops than soil in mustard cover crops, regardless of tillage system. Fewer symphylans were recovered from soil under the spring oat cover crop than soil under the barley cover crop. Eliminating spring tillage may have increased symphylan populations but the effect of reduced tillage on symphylan populations was less important than cover cropping. Predaceous mites were more abundant in soil under large amounts of cover crop residue but these predators were not correlated with lower populations of symphylans. Spring tillage dramatically reduced populations of Pergamasus quisquiliarum , a known predator of symphylans. Cover crops increased both the ratio of predaceous mites to symphylans and the total population of potential prey, thereby, reducing the capacity of predaceous mites to regulate symphylan populations.

Dynamics of soil fungal and bacterial biomass in a temperate climate alley cropping system

Soil bacterial and fungal dynamics were measured in an alley cropping system using direct microscopy techniques. The alley cropping system involved hedgerows of alder trees (Alnus rubra) and sweet corn (Zea mays) grown in the alleys. Trees were periodically coppiced and prunings were incorporated into the soil as green manure. Active fungal and bacterial biomass were greatest in tree rows and declined with distance from the trees. Active fungal biomass was greatest at the first year July sampling, ranging from 44 mg g dry soil ˇ1 in the tree row to 22 mg g dry soil ˇ1 in the middle of the alley. Bacterial biomass in all sampling locations peaked during May before coppicing of trees and cultivation of the alley. Bacterial and fungal biomass in the middle of the alley were similar to sweet corn monocropping plots throughout the growing season. The results suggested that the relatively low pruning biomass that can be produced and incorporated into the soil of temperate climate alley cropping systems compared to tropical alley cropping systems has little effect on microbial biomass. However, additional green manure in the form of leaf fall, additional below ground substrate from tree roots, and favorable conditions in untilled tree rows contribute to higher soil fungal and bacterial counts in and near the tree rows. # 1999 Elsevier Science B.V. All rights reserved.

Effect of Spring Tillage Sequence on Summer Annual Weeds in Vegetable Row Crop Rotations1

The effects of spring tillage sequence on summer annual weed populations were evaluated over two cycles of a 3-yr crop rotation of snap beans, sweet corn, and winter wheat. Continuous no-till (N) planting of vegetable crops each spring (NNNN) reduced summer annual weed density 63 to 86% compared to that of continuous conventional tillage (CCCC), depending upon site and herbicide level. Hairy nightshade populations were reduced by 88 to 96% when spring tillage was eliminated from the crop rotation. The effects of the NNNN spring tillage sequence on weed density were similar at two sites even though the crop rotations at the two sites began with different crops. The rotational tillage sequence of NCNC at the East site, in a crop rotation that began with corn, reduced summer annual weed density by 46 to 51% compared to that of continuous conventional tillage and planting (CCCC) at low and medium herbicide rates, respectively. In contrast, the tillage sequence of CNCN in the same crop rotation and at the same site increased weed density by 80% compared to that of CCCC at a low herbicide rate. The effects of the NCNC and CNCN rotational tillage sequences on weed density were reversed at the West site, and was probably caused by pairing sweet corn with conventional tillage rather than no tillage. The reduction in summer annual weed density caused by reduced spring tillage frequency did not significantly increase crop yields. Nomenclature: Glyphosate; lactofen; metolachlor; barnyardgrass, Echinochloa crus-galli L. Beauv ECHCG; common lambsquarters, Chenopodium album L. CHEAL; hairy nightshade, Solanum sarrachoides Sendtner SOLSA; Powell amaranth, Amaranthus powellii S. Wats AMAPO; redroot pigweed, Amaranthus retroflexus L.; smooth pigweed, Amaranthus hybridus L.; snap beans, Phaseolus vulgaris L. ‘OR91G’; spring barley, Hordeum vulgare L. ‘Micah’; sweet corn Zea mays L. ‘Golden Jubilee’. Additional index words: Conventional tillage, crop rotation, direct-seeding, no-till, rotational tillage, seedbank, seedling recruitment, weed density. Abbreviations: H, high; HL, herbicide level; L, low; M, medium; TS, tillage sequence; WAP, weeks after planting.