scholarly journals Contamination of white clover seed crops by buried seed

1992 ◽  
pp. 139-141
Author(s):  
J.G.H. White ◽  
G.R. Edwards ◽  
K. Nicholson
Keyword(s):  
White Clover ◽  
Burial Depth ◽  
Hard Seed ◽  
Seed Loss ◽  
Cultivation Practices ◽  
Buried Seed ◽  
Direct Drilling ◽  
Clover Seed ◽  
Seed Crops ◽  
Practical Implications

The first study examined white clover seed loss in the offal trail of a header harvester. Seed counts in offal trails were 83 800/m* compared to intermediate areas at 22 500/m*. Consequent problems in sampling for buried seed are discussed. The second trial measured buried seed two years after a white clover seed crop. In the top 25 cm of soil 66 200 seeds/m* remained following conventional cultivation but only 26 000 occurred under direct drilling. With conventional cultivation 80% of seed was buried below 10 cm depth, but 63% of the buried seed was in the O-5 cm layer with direct drilling. In a third study the rate of hard seed breakdown was examined. Breakdown was rapid on the surface but after4 years 36% of seed survived at 10 cm depth and 65% at 20 cm buried. The practical implications on cultivation practices required to permit change of cultivars without contamination problems are discussed. Keywords Trijblium repens L., buried seed, offal trail, direct drill, conventional cultivation, burial depth

scholarly journals POSSIBLE SOLUTIONS TO CONTAMINATION OF WHITE CLOVER SEED CROPS BY BURIED SEED

1985 ◽  
Vol 2 ◽  
pp. 67-73
Author(s):  
P.T.P. Clifford ◽  
M.P. Rolston ◽  
W.M. Williams
Keyword(s):  
White Clover ◽  
Trifolium Repens ◽  
Cultural Practices ◽  
Seeding Rate ◽  
Hard Seed ◽  
Hard Seeds ◽  
Buried Seed ◽  
Trifolium Repens L ◽  
Clover Seed ◽  
Seed Crops

Buried hard seed from seed returned to the soil during harvesting and incorporated by cultivation, poses the greatest threat of contamination. When a different white clover (Trifolium repens L.) is sown, contamination will occur when hard seeds within the germinating zone soften and emerge. Harvest losses can return 40 to 210 kg/ha of hard seeds to the soil. Flowering management and efficient harvesting are necessary to minimise quantities of hard seed returned to the soil. For a buried seed load of 845/m* in the germinating zone of a cultivated seed bed at sowing in March, 8% of that seed load gave rise to establishing plants of which one-third (19/m') were surviving in mid-October. At closing the percentage crop contamination within the sown row was directly proportional to the within-row seeding rate of the sown cultivar. At wider-than-normal row spaces, (45 cm compared with 15 cm) either inter-row cultivation or spraying for removal of contaminants was necessary at closing to reduce contaminants to a density similar to that in 15 cm spacing treatments. Physical contamination of the harvested seedline, compared with levels present at closing, had doubled for normal, but trebled for wider-than-normal spacings. Lowest percentage physical contamination of a seedline gained was 13% for a 6 kg/ha seeding at 15 cm spacings. The results indicate that successful cultivar change on many areas will be difficult. A buried seed count is considered an essential guideline to aid choice of paddock. Future management systems now being developed, include the use of herbicides and direct drilling, and should help to minimise this problem. Keywords: White clover, Trifolium repens, seed production, contamination, cultivar change, harvest losses, hard seed, cultural practices.

scholarly journals CONTAMINATION OF WHITE CLOVER SEED CROPS BY BURIED SEEDS

1985 ◽  
Vol 2 ◽  
pp. 61-65
Author(s):  
J. A. Lancashire ◽  
M.P. Ralston ◽  
D.J. Scott
Keyword(s):  
New Zealand ◽  
White Clover ◽  
Picric Acid ◽  
Morphological Characteristics ◽  
Leaf Size ◽  
Genetic Contamination ◽  
Buried Seed ◽  
Growth Scores ◽  
Clover Seed ◽  
Seed Crops

Thirty five certified seed lines of 'Grasslands Pitau' white clover produced under OECD rules showed marked variations in growth and morphological characteristics according to their region of origin. Of lines grown in Oamaru district, South Canterbury, 90% were significantly different from a Pitau breeders (pre-basic) line in winter growth scores, leaf size and picric acid scores. 90% of lines grown in Marlborough were similar to a Pitau breeders line. Buried white clover seed counts were 260/m' (2 kg/ha) in Marlborough and 1060/m (7.5 kg/ha) in Oamaru. Plants grown from buried seed collected in Canterbury generally had smaller leaves, less winter growth and lower picric acid scores than Pitau. The additional possibility that natural selection of genotypes occurred because some crops of Pitau have been grown under climates and/or managements to which it is not adapted, is also discussed. Preliminary studies of 43 commercial lines of 15 cultivars from 4 countries grown outside New Zealand indicated that 3540% showed significant differences in winter growth and leaf size between lines of the same cultivar. New Zealand grown commercial lines of Huia obtained overseas showed good uniformity. It appears that there is a world-wide problem of genetic contamination in white clover cultivars. High buried seed loads are a potential long term source of contamination which is being exaggerated by the increasing numbers of cultivars. New Zealand has already moved to implement tighter certification standards than those recommended by OECD. Keywords: Trifolium repens, 'Grasslands Pitau', buried seed, seed certification, OECD, genetic contamination.

scholarly journals The key to successful second year white clover seed crops

1996 ◽  
Vol 6 ◽  
pp. 40-40
Author(s):  
B.L. Mccloy ◽  
S.R. White
Keyword(s):  
Seed Yield ◽  
White Clover ◽  
Block Design ◽  
First Year ◽  
Flower Number ◽  
Mature Flower ◽  
Second Year ◽  
Clover Seed ◽  
Seed Crops ◽  
Rotary Type

In recent years there has been an increase in the number of white clover seed crops taken for a second harvest. Traditionally yields from second year crops are substantially lower than first year crops. A trial was established investigating techniques to increase yields in second year crops. The trial was located in a dryland crop of white clover (cv. Grasslands Demand) 4 km east of Methven, mid Canterbury. It involved 10 herbicide treatments and 8 'inter-row' treatments arranged in a split block design. Number of mature flower heads were recorded on all treatments at harvest as an indirect estimate of yield. Additionally, selected treatments were cut and collected using a rotary type mower, threshed, and machine dressed for direct estimates of seed yield. Flower number and machine dressed seed yield were significantly (P

scholarly journals The incidence of insect pests and their Arthropod predators in 24 Canterbury white clover seed crops

1996 ◽  
Vol 6 ◽  
pp. 29-33
Author(s):  
Neil Schroeder ◽  
Peter Clifford
Keyword(s):  
White Clover ◽  
Seed Quality ◽  
Insect Pests ◽  
Arthropod Predators ◽  
Major Injury ◽  
Seed Fill ◽  
Clover Seed ◽  
Seed Crops ◽  
Early Late

Insect pests and their predators were sampled in Canterbury white clover crops during the 1994-95 season. Bluegreen aphid and potato mirids occurred early (late October to mid-November) during the season and were a potential cause of major injury to developing flowerheads. Australian crop mirid, wheat bug, brown shield bug, and spittle bugs occurred later in the season during January and were more likely to affect seed fill and resultant seed quality. Bluegreen aphids reached an overall maximum number of 800 per m2 during early December, while potato mirid nymphs and adults were found in significantly (P

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