Sowing

About: Sowing is a research topic. Over the lifetime, 33888 publications have been published within this topic receiving 273438 citations. The topic is also known as: seeding.

A Comparison of Winter Cereal Species and Planting Dates as Residue Cover for Cotton Grown with Conservation Tillage

Abstract: Winter cereals are often used as cover crops before planting cotton (Gossypium hirsutum L.). Black oat (Avena strigosa Schreb.) is the predominate cereal cover crop for cash crops in southern Brazil and Paraguay, but limited information is available on the suitability of black oat as a cover crop in the southeastern USA. The objectives of this study were to compare black oat with adapted winter cereals for this region and to determine the effect of cereal residue species and amount on cotton growth, N status, and lint yield. In a greenhouse study in which black oat and rye (Secale cereale L.) residues were mixed with soil, tap root elongation of both cotton and radish (Raphanus sativa L.) was inhibited more by black oat residue than by rye residue. In a field experiment on a Goldsboro loamy sand (fine-loamy, siliceous, thermic Aquic Kandiudult), cotton was grown in 1995 and 1996 following black oat, oat (Avena sativa L.), rye, and wheat (Triticum aestivum L.) that were planted at three different times (October, November, and December). AH four winter cereals had similar hiomass production at each planting date in 1995. In 1996, rye was the only species not visibly damaged by a low temperature of -12.2°C that occurred during the winter. Black oat biomass was comparable to wheat in all planting dates but averaged 60% less than rye over all three planting dates and was 37% less than oat in the October planting date in that year. Black oat tended to have a higher N concentration than the other cereal species. Cotton plant density was lowest following black oat and rye. Cotton growth, leaf blade N, and petiole NO 3 -N were more dependent on residue amount than on residue species. Cotton lint yield following black oat was 120 kg ha -1 higher than lint yield of cotton following rye. Cotton following black oat, wheat, and oat had similar lint yield. Black oat may be a promising cover crop for the southeastern USA, but evaluations of other cultivars and/or improvement programs to improve cold hardiness are needed to improve the utility of this species.

Seed dispersal by the Florida box turtle (Terrapene Carolina bauri) in pine rockland forests of the lower Florida Keys, United States

Abstract: Seed dispersal by animals is one of the most important plant-animal mutualisms, but saurochory, the dispersal of seeds by reptiles, has received little attention. We investigated the role of the Florida box turtle (Terrapene carolina bauri) as a seed dispersal agent in pine rockland forests of the lower Florida Keys and examined the effect of turtle digestion on seed germination. We obtained seeds of 11 species with fleshy fruits and 2 species with non-fleshy fruits (a grass and legume) from the feces of 145 box turtles collected on Key Deer National Wildlife Refuge from 1999 to 2000. We planted the seeds of nine species and germination percentage (percentage of seeds that germinated during the experiment) varied from 10% to 80%. Comparative germination experiments were conducted with Thrinax morrissii, Serenoa repens, and Byrsonima lucida. We compared the germination percentage and germination rate (number of days from planting to seedling emergence) of seeds from three treatments (seeds recovered from feces, control seeds with pulp, and control seeds without pulp) and continued these experiments for up to 2 years. Passage through the box turtle digestive tract greatly enhanced the germination percentage and germination rate of S. repens, but decreased the germination percentage of B. lucida and T. morrissii, and decreased germination rate for T. morrissii. Subsequent destructive seed viability tests revealed that many ungerminated T. morrissii seeds remained viable, suggesting long-term seed dormancy may occur, even after passage through the turtle digestive system. In addition, the proportion of ungerminated seeds which remained viable was greater for seeds recovered from turtle feces than from control seeds with pulp. Furthermore, removal of fleshy pulp either manually or by the turtle digestive system may allow T. morrissii to escape insect predation.

Contributions of fixed nitrogen and soil nitrate to the nitrogen economy of irrigated soybean

Abstract: Effects of soil nitrate and numbers of Bradyrhizobium japonicum on the development and functioning of a soybean symbiosis and on crop production were studied in a field experiment at Breeza, New South Wales, Bragg soybean was grown with irrigation on soil, initially free of B. japonicum , with four rates of fertilizer-N (0, 100, 200, 300 kg N ha −1 as ammonium nitrate applied 6 weeks before sowing to provide four concentrations of soil nitrate) and four rates of inoculation [nil, normal (n). 100n, 1000n]. The inoculant strain was B. japonicum CB1809. Observations were made on nodulation, the relative abundance of ureidcs in xylem exudates as an index of N 2 fixation, dry matter and seed yield, and total nitrogen in shoots and seed. Results showed clearly that soil nitrate repressed nodulation, that the effect was magnified as soil nitrate concentrations increased, but that inhibition was substantially ameliorated by increased numbers of rhizobia. The relative abundance of ureides in xylem exudates responded similiarly. The highest yields of dry matter and of N in shoots and in seed occurred at the highest rates of inoculation (100n, 1000n) at intermediate and high soil nitrate (N100, N200, N300); at low soil nitrate (N0), yields were increased by inoculation per se but not by the rate used. Uninoculated plants did not nodulate and yields in these plots reflected concentrations of soil nitrate. Data suggested that soil nitrate and N 2 fixation were not always complementary in meeting the N requirements of the growing crop. Absence of rhizobia. except at the highest rate of nitrate, and repression of nodulation at the normal rate of inoculation by intermediate concentrations of nitrate resulted in reduced N yields because of insufficient N supply to the crop during the final stages of growth.

Germination and early growth of sown Quercus robur L. in relation to soil preparation, sowing depths and prevention against predation

Abstract: A field experiment was established in the autumn of 1992 in order to study predation of acorns, germination and early growth of oak seedlings. The experiment was established on a clearcut and an adjacent oak shelterwood in southern Sweden. In the experiment, a total of 6 840 acorns were sown. The sowing was carried out with different vegetation control and soil preparation treatments and with different planting depths. The germination percentage was highest for acorns sown at five cm depth and lowest for acorns sown on top of the soil, and lower for acorns sown in areas where the humus layer had been removed than in areas where the humus layer was retained. There was no difference in the percentage germination after two growing seasons between acorns sown inside the shelterwood and acorns sown on the clearcut. The height of the seedlings was lowest when the humus was removed while the number of leaves per seedling was lowest for seedlings in untreated areas after two growing seasons. Furthermore, seedlings in untreated areas showed the lowest relative height growth rate during the second growing season. In spite of higher biomass of ground vegetation in undisturbed areas compared to treated areas, no effect of the soil and vegetation control treatments could be found on soil water potentials. The soil temperature and photosynthetic active radiation at seedling level were higher in areas where soil preparation and vegetation control had been performed. However, it was concluded that neither low soil water availability nor low light levels could be the only cause of lower relative height growth rate during the second growing season for seedlings in undisturbed areas.