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 Enquiries SEED News - jan/feb 2008
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This section is coordinated by the professors from the Federal University of Pelotas-Brazil, with the objective of answering the inquiries sent by the readers.
Send your question to e-mail: silmar@seednews.inf.br
"I am an Agricultural Biological Engineer responsible for the production of rice seeds and experiencing doubts as to which would be the best for the cylinder separator. Could you supply information on this issue?"
The cylinder separator removes material from the middle of the seed lot based on differences in seed length; for rice the normal size varies between 7.5mm and 10.0mm, depending on the type. For rice types with long grains it is suggested to use a size of 9.0mm to remove broken grains. Normal seeds will continue their flow within the cylinder, while the broken grains will drop from cylinder pockets while they turn
"I work with a farmer that is interested in growing species that can be used to produce biodiesel. Some time ago I came into possession of the brassicaceae Crambe abyssinica, whose seeds can have up to 40% oil. I was commissioned to study the possibility of producing seed of this species and to take the necessary steps to register and protect the cultivars eventually to be created and developed. Please explain what these steps would involve."
In general, many countries have established schemes to register cultivars so that they can be marketed, and schemes of protection for eventual revenues to cover for the expenses originated during the creation and development of the cultivars. In Brazil, the proceedings needed to register a cultivar are relatively easy, however, when it comes to protection the species it will be required, among other specifications, to be accompanied by a set of agronomic descriptors so as to identify and differentiate the varieties. In reference to this brassicacea species, these descriptors are yet to be defined in Brazilian.
"We are seed growers producing around 2000 tons of rice seeds annually. This year we experienced a 20% rejection of the seed lots due to low seed germination (less than 80%). I would appreciate your comments on the possible causes for this inconvenience."
Rice seeds are normally of high physiological quality due to factors such as post harvest seed dormancy, which minimizes the process of deterioration. Also, harvest is performed at a stage when seed moisture ranges between 20-24%, which helps to reduce field deterioration as seeds remain exposed to the environment for a short period. All these features considered, some abnormal event must have happened to your seeds, and most probably the drying process handled not properly could be one of the reason. Delays on the timing for seed drying and/or a very fast drying process may determine important quality losses. If the rice grains shows also show low industrial yield, then the most probable cause would be related to an high-speed drying process.
"I have found some contradicting information on the relationship between seed vigour and productivity. Could you comment on this issue?"
Many experiments have dealt with the effects of seed vigour on crop productivity but not all of them have found close relationships between both features. Meanwhile, all of the experimental work coincides in that high vigour seed yield better stands, whether in plant population per unit area or dry matter per plant. Furthermore, if we consider the new findings in seed science and technology, some of which have identified intrinsic factors affecting seed performance that can eventually mask the effect of vigour. Controlling other factors, it can be said that vigor does have a close relationship with productivity.
"I have been advised these past years on the need to engage in precision agriculture to maximize yield. Based on those suggestions, I have adopted certain schemes but am experiencing some difficulties to achieve uniform plant stands in my soybean crops. How could I improve this situation?"
The sowing process has had a fast evolution during the last years due to better planters in the market as well as new procedures to standardize the distance between lines. However, emergence within the sowing line is not always uniform, and its consequences on yield vary with the species considered. This heterogeneity can be charged to the sowing process, through factors such as planter speed or sowing depth. However, many times failure to achieve adequate stands can be the result of low quality seeds, which, to some extent can be balanced through higher sowing rates, which may not avoid stand heterogeneity and its impact on the crop yield. Using high quality seed helps plant stand uniformity.
"This year, upon harvesting wheat seed, we verified that none of our seed lots experienced sprouting. Does this indicate that the problem is solved?"
Pre-harvest spike germination or sprouting remains a threat to seed production of species such as wheat, in many regions in which harvest time coincides with the rain season. Meantime, some research programs have achieved success in inserting the dormancy trait into elite varieties, minimizing sprouting, which not only affects seed quality but that of grains for industrial use as well.
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