Seedling Emergence In Field Research Articles

Time of Planting and Diurnal Soil Temperature Effects on Cotton Seedling Field Emergence and Rate of Development

Cotton (Gossypium hirsutum L.) is often planted in early spring before climatic conditions are optimum for seed germination and seedling development. The objective of this study was to determine, in the field, the effect of time of day and cool‐temperature stress from naturally varying soil temperature at a time of planting and following planting on seedling emergence (EMER) and seedling rate of development index (SRDI) for cotton. Seeds of two cultivars (GC‐510 SJ‐2) were planted at 0800 and 1600 h three days a week for 9 wks beginning 24 Feb. 1988 and ending 13 April. Emerging seedlings were counted and ranked according to their stage of development three times a week for 14 wk. Regression analysis was used to determine the time periods when EMER and SRDI were most sensitive to soil temperature. EMER was more sensitive to cool temperature stress when planted at 0800 than at 1600 h during the initial 100 h after planting. The most critical periods of stress for the two cultivars were the same (0800 and 1600 h planting times = +53 and +143 h from planting, respectively. GC‐510 EMER was more sensitive to cool soil temperatures during the initial 100 h after planting than SJ‐2. for both cultivars planted at 1600 h, EMER was similarly sensitive to cool soil temperature at 160 h after planting, a sensitive period not previously described. For neither cultivar was EMER influeced by day‐of‐planting heat units. Time of planting had no effect on SRDI values. GC‐510 SRDI was less‐tolerant of cool soil temperature than SJ‐2 during the initial 30 h from planting (most sensitive at +2 and −6h from planting for 0800 and 1600 h plantings, respectively), but then relatively unaffected by soil temperature. SJ‐2 SRDI was sensitive to cool soil temperature for nearly the entire 160‐h period from the time of planting (most sensitive to cool soil temperature at + 91 and + 138 h after planting for 0800 and 1600 h plantings, respectively). There was no relationship between EMER and SRDI. Cultivars differed in response to cool soil conditions at planting. When cool soil temperature conditions are expected, rapid and high cotton emergence in the field may be achieved by choosing a suited cultivar and by planting in the afternoon.

Influence of Canopy Removal by Burning or Clipping on Emergence of Eragrostis lehmanniana Seedlings

Abstract Eragrostis lehmmniana (Lehrnann lovegrass) is a warm-season bunchgrass native to South Africa which dominates many desert grassland sites in southern Arizona. To determine why fire results in high seedling recruitment of this species, we measured germination of seeds in the seedbank and field seedling emergence following 1) no treatment, 2) burning, 3) clipping and herbicide and 4) herbicide d y . Treatments were designed to compare the effects of initial fire heat treatment with those of canopy removal, as affecting seedbed temperatwe, light and water availability, on seedling emergence. Treatments were replicated over 2 years on a stand of Lehrnann lovegrass at the Santa Rita Experimental Range. Canopy removal, by either clipping or burning, increased seedling emergence in seedbank samples taken prior to summer rains and greatly increased field seeding emergence. High seedling emer- gence after canopy removal was not the result of greater seedbed water availability but probably the result of a greater range in diurnal soil temperatures and increases in red light reaching the seedbed, both of which stimulate germination. The ability of E. lehmanniana to persist after fire indicates that prescribed burning could be used to control associated woody plants and improve forage palat- ability of E. lehmanniana dominated grasslands.

Laboratory Vigor Tests Used to Predict Pepper Seedling Field Emergence Performance

Few investigations have sought to determine the usefulness and repeatability of laboratory vigor tests as predictors of field seedling emergence for multiple locations and years for vegetable crops. The objective of this study was to evaluate a number of previously reported laboratory measures of seed viability and vigor tests that could be used alone, or in combination to reliably predict pepper (Capsicum anuuum L. var. annuum) seedling field emergence. Several indices of seed vigor also were used. The results of these tests were correlated with final field emergence percentages obtained from Davis and Fresno, CA in 1986 and 1987. Either 30 or 32 seed lots were used for each location and year. Measures of seedling growth were the best indicators of field performance and the cool‐temperature (15 °C) percent germination at 14 d was the best overall average single‐test predictor of field emergence for all locations and years. Improved predictions could be made by combining selected vigor tests in multiple regression modes, but these were location and year dependent. An index consisting of the geometric mean of cooltemperature percent germination (Day 14) and seedling dry weight was the best overall average predictor of seedling emergence, accounting for an average of 36% of the total variation in emergence. Simulation trials indicated that a ranking of field performance among seed lots could be done with good success using the geometric mean index.

Seed coat permeability in semi-hard snap bean seeds: its influence on imbibitional chilling injury

SummaryThe susceptibility of a snap bean (Phaseolus vulgaris) breeding line with the semi-hard seed (SHS) characteristic to imbibitional chilling injury was studied. SHS with greater than 10% initial moisture content imbibed water readily. However, at 6% and 8% moisture levels 18 and 6 days were required for full imbibition, respectively. Seed coat permeability of SHS was readily reversible and was moderated by the seed storage relative humidity. Seeds of cv Bush Blue Lake 47 and cv Burly and SHS were adjusted to 12% moisture, and found to be tolerant to imbibitional chilling injury. At 8% moisture only SHS was not susceptible to chilling and this was attributed to slow hydration rates. Mechanical damage of SHS with 8% moisture resulted in increased hydration rates, solute leakage and chilling injury. An improvement in field seedling emergence was measured for SHS compared to the Bush Blue Lake 47 and Burly. SHS exhibited good field emergence at both 8% and 12% moisture.

The influence of a weedy habitat on the seed bank of an adjacent cultivated field

Seed traps positioned 1 to 100 m into a cultivated field were used to assess the seed rain from an adjacent weedy pasture. The cultivated field was in the fallow phase of a crop-fallow rotation. Two sets of traps were used: one set contained steampasteurized soil and the other contained untreated soil from the field. Traps were left in the field for 12 months and then transported to a greenhouse where they were kept for 12 additional months. Seed content was determined by field and greenhouse emergence of seedlings. The pasture was dominated by grasses, the most abundant being Poa pratensis, Stipa comata, Bromus inermis, and Agropyron repens. Seeds of pasture species were found in decreasing numbers in the fallow field, with few found more than 7 m from the fence line in traps of both sterilized and nonsterilized soil. The fallow field was dominated by species such as Setaria viridis, Thlaspi arvense, Descurainia sophia, and Salsola kali which were not found in abundance in the pasture. It was concluded that seed rain from the pasture had a significant influence on the germinable seed content of the soil of the cultivated field (at the edge only). The incursion of pasture species into cultivated land presumably has been restricted by cultural practices.

Relationship Between Weathering Deterioration and Germination, Respiratory Metabolism, and Mineral Leaching from Cottonseeds1

Germination of cottonseeds (Gossypiura hirsutum L.) is reduced by preharvest exposure to,weather, particularly if conditions are warm and humid. To identify some of the germination processes affected by weathering deterioration, seedlots of six cultivars were harvested before and after a period of field exposure and comparative germination studies were conducted. Seedling field emergence was reduced by 11 to 33% due to weathering. During imbibition, weathered seeds of sensitive cultivars released more K+, Mn2+, Mg2+, and Ca2+, but less Na+ into the steep solution than did their unweathered counterparts. Leaching of individual minerals was a better indicator of seed quality than was the total release of electrolytes; release of K+ Ca2+ than was significantly correlated with measurementosf seed quality. Respiratory O2 uptake was reduced in deteriorated seeds, with elevated estimates of the RQ after 7.5 h of imbibition. Aeration with 100% O2 increased O2 uptake and reduced the RQ, indicating that O2 diffusion may have limited respiration during early germination. Weathering deterioration of membranes was confirmed by electron microscopy of cotyledonary lipid and protein bodies. Thesed ata indicate that the loss of membrane functional integrity is a major factor responsible for the reduction of germination potential by weathered seeds, and that the release of K+ and Ca2+ into steep water during imbibition may be a good indicator of cottonseed planting quality.

RELATIONSHIPS OF SEED BANKS TO PLANT DISTRIBUTION PATTERNS IN A FRESHWATER TIDAL WETLAND

Study of seed banks, field seedling emergence, and survival of macrophytes in four zones (steep bank—SB; gentle bank—GB; midbank—MB; high marsh —HM) along transects perpendicular to a stream channel in a freshwater tidal wetland showed that many species are widely distributed. Of the 35 species in the seed bank, 50% were common to all zones; of the 20 species emerging in the field, 77% were observed in all zones. Density of seeds, seedlings, and mature plants of most species, however, varied significantly with habitat. The seed bank of each zone reflected the dominant vegetation of that zone. Most species, even those with high potential for water dispersal, were not evenly distributed. Reciprocal transplants and survival persistence data of dominants corresponded with their habitat preferences. Seed bank densities differed from zone to zone (SB 1,717 m‐2; GB 1,645; MB 2,730; HM 3,620). In all zones the maximum field seedling density was less than the comparable seed bank one (SB 38% less; GB 33%; MB 46%; and HM 10%). These data, coupled with the higher proportion of the total seed bank and total field seedlings occurring in the HM, suggest that the stream channel sites were more stressful early in the growing season than the HM. Because of differential establishment and survival, importance of a species relative to the rest of the vegetation may change with time and occurrence of a species in the vegetation may greatly outweigh its importance in the seed bank or even the seedling stage. Although seeds of annual species were numerous with seven species making up 85% of the seed bank, annual species comprised only about half of the species recorded in the seed bank of each zone. It is not possible at our present level of understanding of seed banks in the freshwater tidal marsh to predict vegetation change. Various combinations of species attributes contribute to the zonation patterns observed in the freshwater tidal wetland.

Effect of seed treatments on field emergence, early growth and some physiological processes of sunflower (Helianthus annuus L.)

Soaking in water or solutions of ascorbic acid, CaCl2, KH2PO4, NaCl, succinic acid and ZnSO4 followed by drying of seeds of sunflower (Helianthus annuus L.), improved field emergence and early growth of seedlings. This seedling vigour is associated with enhanced oxygen uptake, increased amylase activity and the efficiency of mobilizing nutrients from the cotyledons to the embryonic axis.

Progress from Mass Selection for Field Emergence and Seed Weight in a sh2 Population of Maize1

The objective of this study was to evaluate progress from 11 cycles of mass selection for increased field seedling emergence and higher seed weight in a shrunken‐2 (sh2) maize (Zea mays L.) population. Evaluation trials included the 11 cycles of mass selection and four commercial checks homozygous for sh2. The evaluation included field tests, and cold and warm laboratory germination tests of the 15 entries. Field tests were done in nine environments with four replications in each environment. All entries were planted in two‐row plots arranged in a randomized complete block design. Selection for increased field emergence among the 11 cycles of the sh2 population resulted in a significant linear gain of 3.3% per cycle, based on cycle zero. Plant and ear height measurements demonstrated significant correlated increases, while date of flowering showed no significant change. Laboratory germination tests included three replications of 100 seeds for both the cold and warm tests performed in 2 years. The cycles of selection showed significant linear increases in germination percentages for both tests. The phenotypic correlation between field emergence and test weight entry means was highly significant [r = 0.86** (**Significant at the 0.01 level.)]. Phenotypic correlations between field emergence and test weight, and laboratory germination test performance were also significant.

Field emergence of Calabrese and onion seedlings in response to compaction treatments on the soil surface or at seed depth

SummaryThe effects of combinations of soil compaction at seed depth with light or heavy surface compaction on seedling emergence were compared with uncompacted treatments, on nine sowing dates. Integral impedance was affected by surface compaction, rainfall and soil moisture content. Although data from individual sowing dates did not indicate a general relationship between emergence and integral impedance, there were significant negative correlations when the pooled data from all sowing dates were analysed separately for each seed-depth compaction treatment. Calabrese emergence was also related to soil temperature, and onion emergence to soil moisture at sowing. Within sowings the effect of soil compaction was generally detrimental to calabrese but was dependent on soil temperature, whereas only seed-depth compaction after sowing appreciably reduced onion emergence.

Some effects of time of sowing on the first 12 months' growth of ‘Grasslands Huia’ white clover, sown at two seeding rates or associated with ‘Grasslands Manawa’ ryegrass

Abstract ‘Grasslands Huia’ white clover was sown alone at 1030 and 440 seeds/m2, or at 440 seeds with 590 ‘Grasslands Manawa’ ryegrass seeds/m2 in early spring (September), late spring (November), and autumn (March). Field emergence of seedlings was highest from autumn sowing and lowest from late spring sowing. Differences between the clover seeding-rate treatments were dependent upon the length of the period of cool, dark weather between sowing and the commencement of rapid growth in late spring-early summer. Where clover was mixed with Manawa, highest clover yields were obtained from autumn sowing, but highest grass plus clover yields were from late spring sowing. Results are discussed in relation to light, temperature, and competition responses.