Cover crop effects on spring soil water content and the implications for cover crop management in south coastal British Columbia
Soil water content in the spring is an important factor in making decisions on cultural operations. A 2-year study was conducted to determine the effects of fall planted cover crops on spring soil water content dynamics and to relate the water content to cover crop management in terms of field trafficability. Each year, cover crops were planted at two planting dates in the fall, late August and late September on a loamy, mixed, mesic Humaquept on the Fraser River delta, south coastal British Columbia. Treatments were bare (control), wheat, rye and spring barley. Soil samples were collected at approximately bi-weekly intervals beginning in early spring to determine soil water content. Plant samples were also obtained late in the spring to determine C:N ratio. Treatments affected soil water content differently at each sampling date. No differences in soil water content at depths 20�40 and 40�60 cm were observed. Critical soil water content value for trafficability was determined to be 0.32 kg kg-1. Cover crops attained critical C:N ratio of 31.7:1 when the soil water was still above the critical value. The results suggest that terminating the cover crop growth in the spring could best be done by either mowing or spraying the cover crops as opposed to incorporation in order to minimize compaction since the critical C:N ratio for net mineralization is achieved when the soil is still too wet.
Agroecosystems to decrease diffuse nitrogen pollution in Northern Lithuania
AbstractThe paper presents the research conducted at the Joniskėlis Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry on a clay loam Gleyic Cambisol during the period of 2006–2010. The research investigated the changes of mineral nitrogen in soil growing catch crops during the winter wheat post-harvest period and incorporating their biomass into the soil for green manure. Green manure implications for environmental sustainability were assessed. The studies were carried out in the soil with a low (1.90–2.00%) and moderate (2.10–2.40%) humus content in organic and sustainable cropping systems. The crop rotation, expanded in time and space, consisted of red clover (Trifolium pretense L.) → winter wheat (Triticum aestivum L.) → field pea (Pisum sativum L.) → spring barley (Hordeum vulgare L.) with undersown red clover. Investigations of mineral nitrogen migration were assessed in the crop rotation sequence: winter wheat + catch crops → field pea. Higher organic matter and nit...
Seeding Rate and Kill Date Effects on Hairy Vetch‐Cereal Rye Cover Crop Mixtures for Corn Production
Hairy vetch (Vicia villosa Roth) fixes N for corn (Zea mays L.) production, and cereal rye (Secale cereale L.) accumulates soil N to reduce potential N losses. The objective of this research was to identify optimum seeding rates of vetch-rye cover crop mixtures at Coastal Plain and Piedmont locations in Maryland. Mixtures evaluated were 14, 21, and 28 kg vetch ha −1 , and 47 or 94 kg rye ha −1 in complete factorial combination. Pure vetch, rye, and no cover crop were used as controls. Cover crops were killed in early April (early kill) and early May (late kill), followed by no-till corn without fertilizer N. Corn grain yields were signifiantly higher following late-killed covers. Coastal Plain grain yields ranged from 3.1 to 7.0 Mg ha −1 and Piedmont yields ranged from 5.2 to 10.7 Mg ha −1 . Within each kill dade, corn yield was highest following vetch, lowest following rye, and intermediate following all six mixtures. Cover crop yield increased by 160% in the Piedmont and 83% at the Coastal Plain location when kill was delayed. Except for pure rge, N content was 1.6 to 2 times greater by the lad kill date. Total N content was equal for all vetch-rye mixtures at each date and within location, ranging from 74 to 109 kg ha −1 for early kill, and from 136 to 219 kg ha −1 for late kill. Carbon-to-nitrogen ratios (C/N) were <25:1 for all mixture combinations at the Piedmont location and for mixtures with low rye component at the Coastal Plain location. The best seeding rate mixture for corn production was 21 kg vetch ha −1 and 47 kg rye ha −1 .The vetch-rye mixture can scavenge potentially leachable N, while maintaining corn yields by adding fixed N to the cropping system