AGRONOMIJAS VÄSTIS - Latvijas LauksaimniecÄ«bas universitÄte

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<strong>AGRONOMIJAS</strong> VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008335,0085,00A D F co n ten t, g k ḡ 1315,00295,00275,00255,00235,00September 1 September 10 September 20 September 30Harvest timeCP content, g kg -180,0075,0070,0065,00September 1 September 10 September 20 September 30Harvest timeFigure 2. Changes in ADF (left) and CP (right) content in maize yield depending on harvest time( - 2005; 2006)CP content less than 90 g kg -1 was observed in both trial years (Fig. 2, on the right). Strong harvesttime effect (p
<strong>AGRONOMIJAS</strong> VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008The same was noticed for NDF and ADF content in 2006. In addition, concentration of fibrefractions is obviously lower in 2006 if compared with that in 2005 that could be attributed to moremature maize in the same harvest dates in 2006. Similar regularity for NDF and ADF contentdecrease was observed in 2005 from 1 till 20 September, but in the third ten-day period againincrease of these parameters were noticed. Before such phenomenon when NDF and ADF contentincrease at the end of season in Latvia was observed in 2002 (Gaile, 2004) when it was connectedwith maturity stage close to black layer. Darby and Lauer (2002) reported similar data. Situationwas absolutely another in 2005. Strong fall frosts were observed on 17, 18 September 2005, andmaize was frosted. Last ten-day period of September characterised with heavy dew every day,rainstorm in 28 September, and light rain in 30 September. Such wet conditions led to sugar leachfrom the frosted leaves and feed value of stover portion was reduced. NDF and ADF content instover portion during 10-12 days after frosts increased in so high level that grain portion could notdilute it and the whole plant NDF and ADF level also increased. In addition, mould can grow onfrozen leaves, and maize yield could be contaminated with mycotoxins. As fall frosts in differentparts of Latvia in September are usually observed, research of quality changes of frosted maize isneeded.ConclusionsDelayed harvest of maize till 20 September or even later (in 2006) resulted with higheryield, but growers have to consider that in some years (2005) yield increase could be stopped byfall frost.Delayed harvest of maize in September in Latvia resulted mainly in quality increase: DMcontent and corn-cob portion in the whole plant DM yield increased, but NDF and ADF content –decreased. CP content also decreased, but its decrease is unavoidable when we expect mentionedabove improvement of other quality parameters.Killing fall frosts can stop increase of yield and can cause quality decrease if maize is notharvested immediately after frosts. Further research of quality changes after frost are needed takinginto account mould produced micotoxins.AcknowledgementThe study was supported by the grant of Latvian Council of Sciences Num.05.1605.3.References1. Darby H. M., Lauer J.G. (2002) Harvest date and hybrid influence on corn forage yield, quality, andpreservation. Agronomy Journal, 94, 559-566.2. Gaile Z. (2004) Possibility to grow early maturity corn hybrids for energetically dense silage in Latvianconditions. Proceedings of the 4th International Crop Science Congress. – Australia, Brisbane, September 26– October 1. - 6 A4 pages, CD format and available at:www.cropscience.org.au/icsc2004/poster/2/1/3/394_gailez.htm accessed on 02.03.2006.3. Herbert S. J. (1997) Delay corn harvest for maximum yield. Crops, Dairy, Livestock News, Vol. 2:2.www.umass.edu/cdl/publications/c_corn_harvest.htm - accessed on 02.03.2006.4. Keady T.W.J. (2005) Ensiled maize and whole crop wheat forages for beef and dairy cattle: effect onanimal performance. Silage production and utilisation. In: Park R.S., Stronge M.D. (eds) Proceedings of theXIV International Silage, Conference, a satellite workshop of the XXth international Grassland Congress,Wageningen Academic Publishers, the Netherlands, 65-82.5. Lauer J (2003). Keys to higher corn forage yields.www.uwex.edu/ces/forage/wfc/proceedings2003/cornsilageyields.htm - accessed on 02.03.2006.6. Lewis A. L., William J.C., Cherney J.H. (2004) Hybrid, maturity, and cutting height interactions on cornforage yield and quality. Agronomy Journal, 96, 267-274.7. Little E.M., O’Kiely P., Crowley J.C., Keane G.P. Yield and composition of forage maize: interaction ofharvest date, cultivar and plastic mulch. In: Park R.S., Stronge M.D. (eds) Proceedings of the XIVInternational Silage, Conference, a satellite workshop of the XXth international Grassland Congress,Wageningen Academic Publishers, the Netherlands, 176.111
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