The seed ecology of Agriophyllum squarrosum, a pioneer sand dune annual in Central Asia, with particular reference to seed germination

In central Asia, Agriophyllum squarrosum is the first species to become established during natural succession on sand dunes. However, low germination percentages and thus poor stand establishment greatly inhibit the use of this key species in the stabilization of dunes. The aim of this review is to critically analyse published information on the seed biology of A. squarrosum with particular reference to identifying the factors limiting germination of seeds sown in the field. A conceptual model is used to illustrate the complexities of factors as well as the unknowns we found about the seed/seedling stage of the life cycle of this sand dune annual. A major result of this review is that we now know that high germination percentages can be obtained by storing freshly collected seeds dry at room temperatures for 2 to 3 months to allow dormancy break to occur via afterripening, and then storing them dry at low (e.g. 4–5°C) temperature to prevent them from entering secondary dormancy. Non-dormant seeds should be sown in the field in late spring when wind-blown sand will cover them, thus ensuring that they are in darkness, which promotes germination, at the time summer rains occur.

Germination Responses of Purpletop and Big Bluestem Caryopses Subjected to Distilled Water or Potassium Nitrate Prechilling, Sodium Hypochlorite, and Storage

Purpletop [Tridens flavus (L.) Hitchc.] and big bluestem (Andropogon gerardii Vitman) are incorporated into native grass seed mixes for use in ecological restoration. Alleviation of low seed vigor and poor stand establishment would benefit the restoration process by increasing the animal habitat in restored zones. This study determined the effectiveness of prechilling with distilled water (dH2O) versus potassium nitrate (KNO3), sodium hypochlorite (NaOCl) treatments, and short-term storage conditions on seed germination, seedling growth, and stand establishment of purpletop and big bluestem. Prechilling of ‘Niagara, NY Ecotype’ big bluestem for 7 days at 5 °C in dH2O increased final germination percentage (FGP) and germination rate provided caryopses were not dried before sowing. Optimal FGP, germination rate, and germination synchrony were obtained for ‘VA Ecotype’ purpletop after prechilling for 14 days at 5 °C in dH2O without subsequent caryopsis drying or at 0.2% KNO3 with or without subsequent caryopsis drying. Prechilling increased germination synchrony for purpletop but not for big bluestem. NaOCl treatments did not enhance germination or seedling vigor of purpletop or big bluestem. Using nonstored, prechilled caryopses resulted in greater root lengths than stored caryopses or nontreated controls, although optimal purpletop growth required that they be sowed moist, whereas optimal big bluestem growth required that they be dried-back before sowing. In greenhouse experiments, higher seeding rates were correlated with increased number of seedlings for nontreated or prechilled big bluestem and for prechilled purpletop, but not for nontreated purpletop, which had poor stand establishment at all seeding rates. The results indicate that prechilling of caryopses before incorporation into a warm-season grass seed mix increased seedling establishment of purpletop but not big bluestem.

EVALUATING PREPLANT MOISTURIZATION TECHNIQUES FOR IMPROVED FIELD PERFORMANCE OF SHRUNKEN-2 SWEET CORN.

Germination and stand establishment of shrunken-2 sweet corn is a major production-related problem, particularly during early spring in the upper Midwest U.S. Several potential physical and physiological factors have been identified as contributors to poor stand establishment. Poor pericarp integrity and high sucrose levels may lead to non-uniform moisturization and imbibitional injury. Studies were conducted to determine if the use of “controlled moisturization” preplant treatments reduced imbibitional injury and improved germination and seedling vigor. Both laboratory and field results will be discussed.

The placement of fertilizers: I. Root crops

Evidence is adduced to show that sowing the fertilizer in restricted zones or bands gives higher yields of swedes, sugar beet and mangolds than broadcasting and harrowing in fertilizers.Sowing fertilizer in bands at one or both sides of the seed is the most satisfactory method of application. The bands should be about l½ in. from the seed and an inch or so below it. Placing the bands much further away than 1½ in. gives inferior results.Sowing fertilizer in bands at both sides of the seed involves risk of bad sowing, as, on bad seed beds, clods may jam between the fertilizer coulters even if they are staggered. Sowing fertilizer in a single band at the side of the seed obviates this difficulty and sometimes gives higher yields. It is recommended that for swedes, mangolds and sugar beet, complete fertilizers should be sown in one band about 1 in. below and distant laterally about 1½ in. from the seed.On soils very deficient in one or more nutrients, sowing fertilizer in a band below, but not in contact with the seed, gives very good results, but on most soils it is likely to lead to a poor stand of plant and low yields.Sowing fertilizers in the drills in contact with the seed gives good results on soils acutely deficient in one or more nutrients, but it can only be recommended for specific fertilizers in restricted areas (e.g. super-phosphate can be used in this way for swedes on some soils in Wiltshire and Dorset) since it involves serious risk of impaired germination.