{"id":56,"date":"2018-10-01T04:00:28","date_gmt":"2018-10-01T04:00:28","guid":{"rendered":"http:\/\/agrispex.co.za.dedi30.cpt1.host-h.net\/?p=56"},"modified":"2018-10-09T04:22:32","modified_gmt":"2018-10-09T04:22:32","slug":"effektiwiteit-van-kan-teenoor-ureum-by-verskillende-tye-van-toediening-onder-droe-omstandighede-vir-mielies","status":"publish","type":"post","link":"https:\/\/agrispex.co.za\/af\/effektiwiteit-van-kan-teenoor-ureum-by-verskillende-tye-van-toediening-onder-droe-omstandighede-vir-mielies\/","title":{"rendered":"Effektiwiteit van KAN teenoor ureum, by verskillende tye van toediening, onder dro\u00eb omstandighede vir mielies","raw":"Effektiwiteit van KAN teenoor ureum, by verskillende tye van toediening, onder dro\u00eb omstandighede vir mielies"},"content":{"rendered":"

 <\/p>\n

\"\"<\/a>

Dr Erik Adriaanse<\/p><\/div>\n

ENGLISH:\u00a0Efficacy of LAN compared to urea under dry conditions for maize<\/a><\/strong><\/p>\n

Inleiding<\/strong>
\nStikstof (N) word normaalweg onder relatief ho\u00eb re\u00ebnval beter benut wanneer dit later toegedien word, teen 4 tot 8 weke na plant, in vergelyking met voorplant toedienings (Grove et.al.1980). Daarteenoor het toedienings teen 2 weke na plant ho\u00ebr opbrengs gelewer wanneer dit relatief droog is in vergelyking met toedienings teen 5 en 9 weke na plant (Adriaanse and Human 1993).<\/p>\n

\u0149 Nitraat-N: ammonium-N verhouding van 1:1 het ho\u00ebr opbrengs as \u0149 1:0 of 0:1 verhouding gelewer wanneer dit 2 weke na plant toegedien is (Adriaanse and Human, 1993). Soortgelyk is aangetoon dat kombinasies van nitraat en ammonium meer effektief was onder veldtoestande as enige van die twee vorms afsonderlik (Adriaanse, 1990 and Adriaanse and Human, 1991). Wanneer KAN in grondwater oplos is dit reeds in \u0149 1:1 nitraat-N: ammonium-N verhouding en gereed vir gewas-opname. In kontras hiermee is ureum nie tot dieselfde mate geredelik beskikbaar vir opname wanneer dit in grondwater oplos nie. Die tempo van direkte ureum-opname is stadiger as die van ammonium-N of nitraat-N. Ammonium-N sal ook direkte ureum-opname inhibeer. Selfs wanneer nitraat-N konsentrasies 25% minder is as ureum-N konsentrasies sal dit vinniger opgeneem word as ureum-N. Ureum word deur die proses van hidrolise slegs na ammonium omgeskakel en dan verder deur die proses van nitrifikasie na nitraat. Hierdie prosesse mag \u0149 paar dae tot verskeie weke duur. Lae temperature, nat toestande en lae pH sal hierdie prosesse vertraag. Verder is ureum meer toksies, meer loogbaar en meer vervlugtigend as KAN (Adriaanse 2012a).<\/p>\n

Verskeie studies het ho\u00ebr opbrengs vir KAN teenoor ureum aangetoon wanneer dit oor jare en oor lokaliteite vergelyk is (Adriaanse, 2012a, Adriaanse 2012b, Mangle and Hawkins, 1995, Levington Agriculture, 2009, ITGC, 2004, Avails, 1998).<\/p>\n

Die doel van die studie was om KAN en ureum met betrekking tot die volgende onder spesifieke dro\u00eb omstandighede te ondersoek:<\/p>\n

    \n
  1. Die optimum tyd vir N-toedienings.<\/li>\n
  2. Die effektiwiteit van KAN teenoor ureum oor N-peile wat drie weke voor-plant, met-plant en drie weke na plant langs die rye in die grond gebandplaas is.<\/li>\n
  3. Die effektiwiteit van KAN teenoor ureum by verskillende N-peile oor tye van toediening.<\/li>\n<\/ol>\n

    Materiaal and Metodes<\/strong>
    \nNavorsing deur die LNR-IGG in die Viljoenskroondistrik is oor \u2018n 3 jaar tydperk vanaf 1998 tot 2000 op dieselfde persele onderneem. Die grond was van die Avalon-grondvorm met \u2018n sagte plintiet laag wat wissel in diepte van 1.2 m tot 1.7 m. Die klei-inhoude vir verskillende diepte inkremente was 9.1 % van 0 tot 15 cm, 10.4 % van 15 tot 30 cm en 16.0 % van 30 tot 60 cm. Die proef is elke jaar voorafgegaan deur \u2018n rip-op-ry-bewerking tot op \u2018n diepte van 0.6 tot 0.7 m.<\/p>\n

    Behandelings het uit 5 stikstof-peile (35 tot 175 kg N\/ha, 3 tye van toediening (voor-plant, met-plant of na-plant) en 2 N-bronne (KAN of Ureum) plus 2 kontroles (0 kg N\/ha) bestaan wat faktoriaal gekombineer is in \u2018n ewekansige blokontwerp en twee keer herhaal is. Toediening was 3 weke voor-plant, met-plant of 3 weke na-plant 10 tot 15 cm vanaf die rye op \u2018n diepte van 10 cm met die hand. Behalwe in die geval van die kontrole, is 20 kg N van elke N-peil in die vorm van KAN saam met 30 kg P\/ha (Dubbelsuperfosfaat 20%) en 30 kg K\/ha (Kaliumchloriet) 5 cm weg en 5 cm dieper as die saad met \u2018n gespesialiseerde planter met planttyd gebandplaas. Die mielie-kultivar PANNAR 6479 is by ry-wydtes van 1.5 m geplant. Plantdatums was 18\/12\/97, 23\/11\/98 en 5\/12\/99 by effektiewe plantestande van 26 514, 27 083 en 25 069 plante\/ha onderskeidelik vir die drie seisoene.<\/p>\n

    Slegs die resultate van die laaste seisoen is geselekteer om die spesifieke effek van \u0149 dro\u00eb periode na plant te ondersoek. Behandelingseffekte oor seisoene is voorheen gerapporteer (Adriaanse 2012a, Adriaanse 2012b).<\/p>\n

    Re\u00ebnval<\/strong>
    \nRe\u00ebnvalverspreidingsverskille tussen seisoene word in Tabel 1 aangedui. Re\u00ebnval vir die groeiperiode van die eerste seisoen (1997\/98) was die laagste, gevolg deur die tweede seisoen (1998\/99) en dan die derde seisoen (1999\/00) wat die hoogste was. Die eerste effektiewe re\u00ebn het egter later na plant vir die laaste seisoen gekom as vir die ander seisoene. Verder hiertoe was die hoeveelheid effektiewe re\u00ebn, die maksimum re\u00ebn binne 30 dae na plant en die totale re\u00ebnval vir die 30 dae periode na plant baie laer vir die laaste seisoen in vergelyking met die eerste twee seisoene. Slegs die resultate van die laaste seisoen is daarom vir verdere bespreking geselekteer.<\/p>\n

    \"\"<\/a>

    Tabel 1: Re\u00ebnvalverspreidingsverskille tussen seisoene (LNR-IGG, Navorsingsverslag, 2000).<\/p><\/div>\n

    Resultate en bespreking<\/strong>
    \nOptimum tyd van N-toedienings
    \nDie mees effektiewe tyd van N-toediening vir beide N-bronne was 3 weke na-plant, gevolg deur voor-plant-toedienings en dan met-plant-toedienings wat minder effektief was (Figuur 1). Hierdie tendens was soortgelyk oor seisoene soos wat voorheen gerapporteer is (Adriaanse, 2012a; Adriaanse, F. G., 2012b.) behalwe vir KAN wat beter oor seisoene presteer het wanneer met-plant toegedien is teenoor voor-plant-toedienings.
    \nDie effektiwiteit van KAN teenoor ureum by tye van toediening oor N-peile.
    \nKAN was meer effektief as ureum oor N-peile veral vir met-plant-toedienings, maar ook vir voor-plant- en na-plant-toedienings (Figuur 1). Die opbrengs wat met KAN verkry is was 3.2 ton\/ha ho\u00ebr as wat met ureum vir met-plant-toedienings verkry is (Figuur 1). Ammoniak-vergiftiging weens die bandplasing van ureum by ry-wydtes van 1.5 m, wat ho\u00eb konsentrasies onder dro\u00eb toestande tot gevolg gehad het, was waarskynlik hoofsaaklik hiervoor verantwoordelik. Onvoldoende re\u00ebn na-plant sou die vertikale verspreiding van ureum beperk het en dit dus verder gekonsentreer het. Ammoniak-vervlugtiging van \u0149 diepte van 10 cm in \u0149 sanderige grond het waarskynlik ook tot die negatiewe effek van gekonsentreerde ureum bygedra.<\/p>\n

    Die risiko van \u0149 opbrengsverlies weens \u0149 dro\u00eb periode na plant sal verseker baie minder wees wanneer KAN by voorkeur bo ureum gebruik word (Figuur 1). Die uitstel van N-toedienings tot 3 weke na plant was ook betekenisvol beter as om alle N met-plant toe te dien vir beide N-bronne (Figuur 1). KAN-toedienings teen 3 weke na-plant was ook betekenisvol beter as ureum toedienings voor-plant (Figuur 1).<\/p>\n

    \"\"<\/a>

    Figuur 1. Opbrengs-reaksie op tye van toediening vir die 1999\/2000 seisoen oor N-peile (LNR-IGG, Navorsingsverslag, 2000). Kleinste betekenisvolle verskil (0.05) = 687 kg\/ha<\/p><\/div>\n

    Die effektiwiteit van KAN teenoor ureum by verskillende N-peile oor tye van toediening
    \nDie opbrengs-reaksie op ho\u00ebr N-peile was baie beter vir KAN as vir ureum (Figuur 2). Bandgeplaasde ureum-N toedienings van meer as 15 kg\/ha (35 minus 20 kg N\/ha in die plantmengsel) het baie minder opbrengs gelewer as KAN by vergelykbare N-peile (Figuur 2). Opbrengs by 155 kg KAN-N\/ha was 3.0 ton\/ha meer as met ureum by dieselfde N-peil (Figuur 2). Hierdie verskil word hoofsaaklik aan ammoniak-vergiftiging maar waarskynlik ook ammoniak-vervlugtiging weens gekonsentreerde ureum tydens dro\u00eb omstandighede toegeskryf.<\/p>\n

    \"\"<\/a>

    Figuur 2. Opbrengs-reaksie op N-peile vir KAN en ureum oor tye van toediening vir die 1999\/2000 seisoen. Met plant is 20 kg N\/ha van elke N-peil, behalwe die kontrole as KAN in die plantmengsel toegedien (LNR-IGG, Navorsingsverslag, 2000).<\/p><\/div>\n

    Gevolgtrekkings<\/strong><\/p>\n

    N-toedienings teen 3 weke na plant is meer effektief as 3 weke voor-plant en baie meer effektief as met-plant vir albei N-bronne.
    \nHo\u00ebr opbrengs vir KAN in vergelyking met ureum oor N-peile is vir alle tyd-behandelings verkry. Hierdie verskil in opbrengs was egter die grootste vir met-plant-toedienings. Die opbrengs wat so vir met-plant-toedienings met KAN verkry is was 3.2 ton\/ha of 177% meer as wat met ureum verkry is.
    \nKAN het baie beter op ho\u00ebr N-peile gereageer as ureum wanneer oor tye van toediening vergelyk is. Hierdie effek is by meer as 15 kg N\/ha waargeneem. Die opbrengs wat so met KAN by 155 kg N\/ha verkry is was 3.0 ton\/ha of 88% ho\u00ebr as wat met ureum by dieselfde N-peil verkry is.<\/p>\n

    Risikobestuur<\/strong><\/span><\/p>\n

    Risiko word verminder deur die meeste N na-plant toe te dien eerder as voor-plant of met-plant. In relatief dro\u00ebr dele (< 700 mm re\u00ebn \/jaar) is die aanbeveling 3 tot 4 weke na-plant en in relatief natter gebiede (>700 mm re\u00ebn \/jaar) 4 tot 6 weke na plant. Deur vooraf op die praktyk van na-plant toedienings vir die meeste N te besluit word die neem van risiko weens droogte uitgestel of verminder. Wanneer dit duidelik word dat die seisoen verder baie droog gaan wees kan N-peile afwaarts aangepas word of geen verdere N gegee word nie ten einde risiko van winsverlies te verminder.<\/span><\/p>\n

    Die risiko van \u0149 betekenisvolle opbrengsverlies weens \u0149 dro\u00eb periode na-plant is baie groter wanneer ureum as die hoof N-bron gebandplaas word in vergelyking met KAN. Hierdie risiko is vir verskillende tye van toediening van toepassing, maar veral vir met-plant toedienings. Hierdie risiko is ook oor tye van toediening vanaf relatief lae ureum-N-peile van toepassing.<\/span><\/p>\n

    Let Wel: Raadpleeg \u2018n gekwalifiseerde landboukundige vir meer lokaliteit spesifieke toepassings. Die resultate waarna in hierdie artikel verwys word, is onder spesifieke omstandighede verkry en daarom nie algemeen onder alle omstandighede toepasbaar nie.<\/strong><\/p>\n

    Verwysings<\/strong><\/p>\n

    ADRIAANSE F.G., 1990. Effects of nitrate: ammonium ratios, times of application and prolificacy on nitrogen response of Zea mays L. Ph. D. University of the Free State.<\/p>\n

    ADRIAANSE, F. G., & HUMAN J.J., 1991. The effects of nitrate: ammonium ratios and dicyandiamide on the nitrogen response of Zea Mays L. in a high rainfall area on an acid soil. Plant and Soil 135, 43-52.<\/p>\n

    ADRIAANSE, F. G., 2012a, Efficacy and application of nitrogen sources. The Fertilizer Society of South Africa Journal.<\/p>\n

    ADRIAANSE, F. G., 2012b. KAN of ureum : voor-plant, met-plant of na-plant S A
    \nGraan\/Grain. 5\/12.<\/p>\n

    ADRIAANSE, F. G., & HUMAN J.J., 1993. Effect of time of application and nitrate:
    \nammonium ratios on maize grain yield, grain N concentration and soil mineral N
    \nconcentration in a semi-arid region. Field Crops Research 34, 57-70.<\/p>\n

    AVAILS, 1998, Official advisory service, France<\/p>\n

    GROVE, T.L., RITCHEY, K.D.& NADERMAN, G.C.,1980. Nitrogen fertilization of maize on an oxisol of the Cerrado of Brazil. AGRON. J.,72:261-265<\/p>\n

    MANGIE & HAWKINS, 1995. Penchant Manual. Purdue University, West Lafayette Indiana, USA.
    \nITGC, 2004. Instituto T\u00e9cnicode Gesti\u00f3n del Cereal, Spain.
    \nLEVINGTON AGRICULTURE UK, 2009. In M. Basten. Fertiliser quality and the environment. The Fertilizer Society of South Africa Journal, 2009.<\/p>\n","protected":false,"raw":" \r\n\r\n[caption id=\"attachment_1270\" align=\"alignright\" width=\"150\"]    \"\"<\/a> Dr Erik Adriaanse[\/caption]\r\n\r\nENGLISH:\u00a0Efficacy of LAN compared to urea under dry conditions for maize<\/a><\/strong>\r\n\r\nInleiding<\/strong>\r\nStikstof (N) word normaalweg onder relatief ho\u00eb re\u00ebnval beter benut wanneer dit later toegedien word, teen 4 tot 8 weke na plant, in vergelyking met voorplant toedienings (Grove et.al.1980). Daarteenoor het toedienings teen 2 weke na plant ho\u00ebr opbrengs gelewer wanneer dit relatief droog is in vergelyking met toedienings teen 5 en 9 weke na plant (Adriaanse and Human 1993).\r\n\r\n\u0149 Nitraat-N: ammonium-N verhouding van 1:1 het ho\u00ebr opbrengs as \u0149 1:0 of 0:1 verhouding gelewer wanneer dit 2 weke na plant toegedien is (Adriaanse and Human, 1993). Soortgelyk is aangetoon dat kombinasies van nitraat en ammonium meer effektief was onder veldtoestande as enige van die twee vorms afsonderlik (Adriaanse, 1990 and Adriaanse and Human, 1991). Wanneer KAN in grondwater oplos is dit reeds in \u0149 1:1 nitraat-N: ammonium-N verhouding en gereed vir gewas-opname. In kontras hiermee is ureum nie tot dieselfde mate geredelik beskikbaar vir opname wanneer dit in grondwater oplos nie. Die tempo van direkte ureum-opname is stadiger as die van ammonium-N of nitraat-N. Ammonium-N sal ook direkte ureum-opname inhibeer. Selfs wanneer nitraat-N konsentrasies 25% minder is as ureum-N konsentrasies sal dit vinniger opgeneem word as ureum-N. Ureum word deur die proses van hidrolise slegs na ammonium omgeskakel en dan verder deur die proses van nitrifikasie na nitraat. Hierdie prosesse mag \u0149 paar dae tot verskeie weke duur. Lae temperature, nat toestande en lae pH sal hierdie prosesse vertraag. Verder is ureum meer toksies, meer loogbaar en meer vervlugtigend as KAN (Adriaanse 2012a).\r\n\r\nVerskeie studies het ho\u00ebr opbrengs vir KAN teenoor ureum aangetoon wanneer dit oor jare en oor lokaliteite vergelyk is (Adriaanse, 2012a, Adriaanse 2012b, Mangle and Hawkins, 1995, Levington Agriculture, 2009, ITGC, 2004, Avails, 1998).\r\n\r\nDie doel van die studie was om KAN en ureum met betrekking tot die volgende onder spesifieke dro\u00eb omstandighede te ondersoek:\r\n

      \r\n \t
    1. Die optimum tyd vir N-toedienings.<\/li>\r\n \t
    2. Die effektiwiteit van KAN teenoor ureum oor N-peile wat drie weke voor-plant, met-plant en drie weke na plant langs die rye in die grond gebandplaas is.<\/li>\r\n \t
    3. Die effektiwiteit van KAN teenoor ureum by verskillende N-peile oor tye van toediening.<\/li>\r\n<\/ol>\r\nMateriaal and Metodes<\/strong>\r\nNavorsing deur die LNR-IGG in die Viljoenskroondistrik is oor \u2018n 3 jaar tydperk vanaf 1998 tot 2000 op dieselfde persele onderneem. Die grond was van die Avalon-grondvorm met \u2018n sagte plintiet laag wat wissel in diepte van 1.2 m tot 1.7 m. Die klei-inhoude vir verskillende diepte inkremente was 9.1 % van 0 tot 15 cm, 10.4 % van 15 tot 30 cm en 16.0 % van 30 tot 60 cm. Die proef is elke jaar voorafgegaan deur \u2018n rip-op-ry-bewerking tot op \u2018n diepte van 0.6 tot 0.7 m.\r\n\r\nBehandelings het uit 5 stikstof-peile (35 tot 175 kg N\/ha, 3 tye van toediening (voor-plant, met-plant of na-plant) en 2 N-bronne (KAN of Ureum) plus 2 kontroles (0 kg N\/ha) bestaan wat faktoriaal gekombineer is in \u2018n ewekansige blokontwerp en twee keer herhaal is. Toediening was 3 weke voor-plant, met-plant of 3 weke na-plant 10 tot 15 cm vanaf die rye op \u2018n diepte van 10 cm met die hand. Behalwe in die geval van die kontrole, is 20 kg N van elke N-peil in die vorm van KAN saam met 30 kg P\/ha (Dubbelsuperfosfaat 20%) en 30 kg K\/ha (Kaliumchloriet) 5 cm weg en 5 cm dieper as die saad met \u2018n gespesialiseerde planter met planttyd gebandplaas. Die mielie-kultivar PANNAR 6479 is by ry-wydtes van 1.5 m geplant. Plantdatums was 18\/12\/97, 23\/11\/98 en 5\/12\/99 by effektiewe plantestande van 26 514, 27 083 en 25 069 plante\/ha onderskeidelik vir die drie seisoene.\r\n\r\nSlegs die resultate van die laaste seisoen is geselekteer om die spesifieke effek van \u0149 dro\u00eb periode na plant te ondersoek. Behandelingseffekte oor seisoene is voorheen gerapporteer (Adriaanse 2012a, Adriaanse 2012b).\r\n\r\nRe\u00ebnval<\/strong>\r\nRe\u00ebnvalverspreidingsverskille tussen seisoene word in Tabel 1 aangedui. Re\u00ebnval vir die groeiperiode van die eerste seisoen (1997\/98) was die laagste, gevolg deur die tweede seisoen (1998\/99) en dan die derde seisoen (1999\/00) wat die hoogste was. Die eerste effektiewe re\u00ebn het egter later na plant vir die laaste seisoen gekom as vir die ander seisoene. Verder hiertoe was die hoeveelheid effektiewe re\u00ebn, die maksimum re\u00ebn binne 30 dae na plant en die totale re\u00ebnval vir die 30 dae periode na plant baie laer vir die laaste seisoen in vergelyking met die eerste twee seisoene. Slegs die resultate van die laaste seisoen is daarom vir verdere bespreking geselekteer.\r\n\r\n[caption id=\"attachment_1394\" align=\"aligncenter\" width=\"820\"]\"\"<\/a> Tabel 1: Re\u00ebnvalverspreidingsverskille tussen seisoene (LNR-IGG, Navorsingsverslag, 2000).[\/caption]\r\n\r\nResultate en bespreking<\/strong>\r\nOptimum tyd van N-toedienings\r\nDie mees effektiewe tyd van N-toediening vir beide N-bronne was 3 weke na-plant, gevolg deur voor-plant-toedienings en dan met-plant-toedienings wat minder effektief was (Figuur 1). Hierdie tendens was soortgelyk oor seisoene soos wat voorheen gerapporteer is (Adriaanse, 2012a; Adriaanse, F. G., 2012b.) behalwe vir KAN wat beter oor seisoene presteer het wanneer met-plant toegedien is teenoor voor-plant-toedienings.\r\nDie effektiwiteit van KAN teenoor ureum by tye van toediening oor N-peile.\r\nKAN was meer effektief as ureum oor N-peile veral vir met-plant-toedienings, maar ook vir voor-plant- en na-plant-toedienings (Figuur 1). Die opbrengs wat met KAN verkry is was 3.2 ton\/ha ho\u00ebr as wat met ureum vir met-plant-toedienings verkry is (Figuur 1). Ammoniak-vergiftiging weens die bandplasing van ureum by ry-wydtes van 1.5 m, wat ho\u00eb konsentrasies onder dro\u00eb toestande tot gevolg gehad het, was waarskynlik hoofsaaklik hiervoor verantwoordelik. Onvoldoende re\u00ebn na-plant sou die vertikale verspreiding van ureum beperk het en dit dus verder gekonsentreer het. Ammoniak-vervlugtiging van \u0149 diepte van 10 cm in \u0149 sanderige grond het waarskynlik ook tot die negatiewe effek van gekonsentreerde ureum bygedra.\r\n\r\nDie risiko van \u0149 opbrengsverlies weens \u0149 dro\u00eb periode na plant sal verseker baie minder wees wanneer KAN by voorkeur bo ureum gebruik word (Figuur 1). Die uitstel van N-toedienings tot 3 weke na plant was ook betekenisvol beter as om alle N met-plant toe te dien vir beide N-bronne (Figuur 1). KAN-toedienings teen 3 weke na-plant was ook betekenisvol beter as ureum toedienings voor-plant (Figuur 1).\r\n\r\n[caption id=\"attachment_1396\" align=\"aligncenter\" width=\"711\"]\"\"<\/a> Figuur 1. Opbrengs-reaksie op tye van toediening vir die 1999\/2000 seisoen oor N-peile (LNR-IGG, Navorsingsverslag, 2000). Kleinste betekenisvolle verskil (0.05) = 687 kg\/ha[\/caption]\r\n\r\nDie effektiwiteit van KAN teenoor ureum by verskillende N-peile oor tye van toediening\r\nDie opbrengs-reaksie op ho\u00ebr N-peile was baie beter vir KAN as vir ureum (Figuur 2). Bandgeplaasde ureum-N toedienings van meer as 15 kg\/ha (35 minus 20 kg N\/ha in die plantmengsel) het baie minder opbrengs gelewer as KAN by vergelykbare N-peile (Figuur 2). Opbrengs by 155 kg KAN-N\/ha was 3.0 ton\/ha meer as met ureum by dieselfde N-peil (Figuur 2). Hierdie verskil word hoofsaaklik aan ammoniak-vergiftiging maar waarskynlik ook ammoniak-vervlugtiging weens gekonsentreerde ureum tydens dro\u00eb omstandighede toegeskryf.\r\n\r\n[caption id=\"attachment_1398\" align=\"aligncenter\" width=\"711\"]\"\"<\/a> Figuur 2. Opbrengs-reaksie op N-peile vir KAN en ureum oor tye van toediening vir die 1999\/2000 seisoen. Met plant is 20 kg N\/ha van elke N-peil, behalwe die kontrole as KAN in die plantmengsel toegedien (LNR-IGG, Navorsingsverslag, 2000).[\/caption]\r\n\r\nGevolgtrekkings<\/strong>\r\n\r\nN-toedienings teen 3 weke na plant is meer effektief as 3 weke voor-plant en baie meer effektief as met-plant vir albei N-bronne.\r\nHo\u00ebr opbrengs vir KAN in vergelyking met ureum oor N-peile is vir alle tyd-behandelings verkry. Hierdie verskil in opbrengs was egter die grootste vir met-plant-toedienings. Die opbrengs wat so vir met-plant-toedienings met KAN verkry is was 3.2 ton\/ha of 177% meer as wat met ureum verkry is.\r\nKAN het baie beter op ho\u00ebr N-peile gereageer as ureum wanneer oor tye van toediening vergelyk is. Hierdie effek is by meer as 15 kg N\/ha waargeneem. Die opbrengs wat so met KAN by 155 kg N\/ha verkry is was 3.0 ton\/ha of 88% ho\u00ebr as wat met ureum by dieselfde N-peil verkry is.\r\n\r\nRisikobestuur<\/strong><\/span>\r\n\r\nRisiko word verminder deur die meeste N na-plant toe te dien eerder as voor-plant of met-plant. In relatief dro\u00ebr dele (< 700 mm re\u00ebn \/jaar) is die aanbeveling 3 tot 4 weke na-plant en in relatief natter gebiede (>700 mm re\u00ebn \/jaar) 4 tot 6 weke na plant. Deur vooraf op die praktyk van na-plant toedienings vir die meeste N te besluit word die neem van risiko weens droogte uitgestel of verminder. Wanneer dit duidelik word dat die seisoen verder baie droog gaan wees kan N-peile afwaarts aangepas word of geen verdere N gegee word nie ten einde risiko van winsverlies te verminder.<\/span>\r\n\r\nDie risiko van \u0149 betekenisvolle opbrengsverlies weens \u0149 dro\u00eb periode na-plant is baie groter wanneer ureum as die hoof N-bron gebandplaas word in vergelyking met KAN. Hierdie risiko is vir verskillende tye van toediening van toepassing, maar veral vir met-plant toedienings. Hierdie risiko is ook oor tye van toediening vanaf relatief lae ureum-N-peile van toepassing.<\/span>\r\n\r\nLet Wel: Raadpleeg \u2018n gekwalifiseerde landboukundige vir meer lokaliteit spesifieke toepassings. Die resultate waarna in hierdie artikel verwys word, is onder spesifieke omstandighede verkry en daarom nie algemeen onder alle omstandighede toepasbaar nie.<\/strong>\r\n\r\nVerwysings<\/strong>\r\n\r\nADRIAANSE F.G., 1990. Effects of nitrate: ammonium ratios, times of application and prolificacy on nitrogen response of Zea mays L. Ph. D. University of the Free State.\r\n\r\nADRIAANSE, F. G., & HUMAN J.J., 1991. The effects of nitrate: ammonium ratios and dicyandiamide on the nitrogen response of Zea Mays L. in a high rainfall area on an acid soil. Plant and Soil 135, 43-52.\r\n\r\nADRIAANSE, F. G., 2012a, Efficacy and application of nitrogen sources. The Fertilizer Society of South Africa Journal.\r\n\r\nADRIAANSE, F. G., 2012b. KAN of ureum : voor-plant, met-plant of na-plant S A\r\nGraan\/Grain. 5\/12.\r\n\r\nADRIAANSE, F. G., & HUMAN J.J., 1993. Effect of time of application and nitrate:\r\nammonium ratios on maize grain yield, grain N concentration and soil mineral N\r\nconcentration in a semi-arid region. Field Crops Research 34, 57-70.\r\n\r\nAVAILS, 1998, Official advisory service, France\r\n\r\nGROVE, T.L., RITCHEY, K.D.& NADERMAN, G.C.,1980. Nitrogen fertilization of maize on an oxisol of the Cerrado of Brazil. AGRON. J.,72:261-265\r\n\r\nMANGIE & HAWKINS, 1995. Penchant Manual. Purdue University, West Lafayette Indiana, USA.\r\nITGC, 2004. Instituto T\u00e9cnicode Gesti\u00f3n del Cereal, Spain.\r\nLEVINGTON AGRICULTURE UK, 2009. In M. Basten. Fertiliser quality and the environment. The Fertilizer Society of South Africa Journal, 2009."},"excerpt":{"rendered":"  Dr Erik Adriaanse AFRIKAANS:\u00a0Effektiwiteit van KAN teenoor ureum, by verskillende tye van toediening, onder dro\u00eb omstandighede vir mielies Introduction Nitrogen (N) is normally more efficiently utilized when applied 4 to 8 weeks after planting under high rainfall conditions compared to pre-plant applications (Grove et. al., 1980). In contrast, most N applied 2 weeks after planting showed higher yields than later applications at 5 and 9 weeks after planting under relatively dry conditions (Adriaanse and Human 1993). For applications, 2 weeks after planting a nitrate-N: ammonium-N ratio of 1:1 resulted in higher yield than a 1:0 or 0:1 ratio (Adriaanse and Human, 1993). Similarly it was demonstrated that combinations of nitrate and ammonium were better than either ammonium or nitrate on their own under field conditions (Adriaanse, 1990 and Adriaanse and Human, 1991). When LAN dissolves in soil water it is already in a 1:1 nitrate-N: ammonium-N ratio and readily available for uptake. In contrast urea is not readily available for uptake to the same extent when dissolved in soil water. The rate of direct urea uptake is slower than for either ammonium-N or nitrate-N. Ammonium-N will also inhibit direct urea uptake. Even if nitrate-N concentration is 25% less than urea-N it will still be taken up quicker than urea-N. After hydrolysis, urea will firstly result in a 0:1 nitrate-N: ammonium-N ratio and only after nitrification will more ammonium be converted to nitrate. The time period for these processes to take place may vary from a few days to several weeks. Low temperatures, wet conditions and low soil pH will delay these processes. In addition urea is more toxic, leaches more and is more volatile compared to LAN (Adriaanse 2012a). Many studies have shown better yield responses to LAN compared to urea in long term trials over years as well as over different localities (Adriaanse, 2012a, Adriaanse 2012b, Mangle and Hawkins, 1995, Levington Agriculture, 2009, ITGC, 2004, Avails, 1998). The objectives of this study under a particular dry season were to determine: The optimum timing of N-applications. The efficacy of LAN compared to urea applied 3 weeks before planting, at planting and 3 weeks after planting over different N-rates as knifed in side dressings. To determine the efficacy of LAN compared to urea at different N-rates over time treatments. Materials and Methods Research done by the ARC-GCI in the Viljoenskroon district was carried out over a three year period from 1998 to 2000 on the same plots. The long term annual rainfall average for this area was 592 mm. The soil was from the Avalon form (RSA) or Luvisol (international) containing a soft plinthic layer, varying in depth from 1.2 m to 1.7 m. The soil clay content for different depth increments was 9.1 % from 0 to 15 cm, 10.4 % from 15 to 30 cm and 16.0 % from 30 to 60 cm. Under these specific conditions nitrogen will leach to reach the water in the water table, but it will also move upwards with the water table....","protected":false,"raw":""},"author":15,"featured_media":1397,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_en_post_content":" \r\n\r\n[caption id=\"attachment_1270\" align=\"alignright\" width=\"150\"]\"\"<\/a> Dr Erik Adriaanse[\/caption]\r\n\r\nAFRIKAANS:\u00a0Effektiwiteit van KAN teenoor ureum, by verskillende tye van toediening, onder dro\u00eb omstandighede vir mielies<\/a><\/strong>\r\n\r\nIntroduction<\/strong>\r\nNitrogen (N) is normally more efficiently utilized when applied 4 to 8 weeks after planting under high rainfall conditions compared to pre-plant applications (Grove et. al., 1980). In contrast, most N applied 2 weeks after planting showed higher yields than later applications at 5 and 9 weeks after planting under relatively dry conditions (Adriaanse and Human 1993).\r\n\r\nFor applications, 2 weeks after planting a nitrate-N: ammonium-N ratio of 1:1 resulted in higher yield than a 1:0 or 0:1 ratio (Adriaanse and Human, 1993). Similarly it was demonstrated that combinations of nitrate and ammonium were better than either ammonium or nitrate on their own under field conditions (Adriaanse, 1990 and Adriaanse and Human, 1991). When LAN dissolves in soil water it is already in a 1:1 nitrate-N: ammonium-N ratio and readily available for uptake. In contrast urea is not readily available for uptake to the same extent when dissolved in soil water. The rate of direct urea uptake is slower than for either ammonium-N or nitrate-N. Ammonium-N will also inhibit direct urea uptake. Even if nitrate-N concentration is 25% less than urea-N it will still be taken up quicker than urea-N. After hydrolysis, urea will firstly result in a 0:1 nitrate-N: ammonium-N ratio and only after nitrification will more ammonium be converted to nitrate. The time period for these processes to take place may vary from a few days to several weeks. Low temperatures, wet conditions and low soil pH will delay these processes. In addition urea is more toxic, leaches more and is more volatile compared to LAN (Adriaanse 2012a).\r\n\r\nMany studies have shown better yield responses to LAN compared to urea in long term trials over years as well as over different localities (Adriaanse, 2012a, Adriaanse 2012b, Mangle and Hawkins, 1995, Levington Agriculture, 2009, ITGC, 2004, Avails, 1998).\r\n\r\nThe objectives of this study under a particular dry season were to determine:\r\n
        \r\n \t
      1. The optimum timing of N-applications.<\/li>\r\n \t
      2. The efficacy of LAN compared to urea applied 3 weeks before planting, at planting and 3 weeks after planting over different N-rates as knifed in side dressings.<\/li>\r\n \t
      3. To determine the efficacy of LAN compared to urea at different N-rates over time treatments.<\/li>\r\n<\/ol>\r\nMaterials and Methods<\/strong>\r\nResearch done by the ARC-GCI in the Viljoenskroon district was carried out over a three year period from 1998 to 2000 on the same plots. The long term annual rainfall average for this area was 592 mm. The soil was from the Avalon form (RSA) or Luvisol (international) containing a soft plinthic layer, varying in depth from 1.2 m to 1.7 m. The soil clay content for different depth increments was 9.1 % from 0 to 15 cm, 10.4 % from 15 to 30 cm and 16.0 % from 30 to 60 cm. Under these specific conditions nitrogen will leach to reach the water in the water table, but it will also move upwards with the water table. Leaching of nitrogen is therefore restricted and movement of water in the sub soil is also much slower due to the higher clay content. Every year the trial was preceded by a rip on row tillage practice to a depth of 0.6 to 0.7 m.\r\nTreatments consisted of five N rates (35 to 175 kg N\/ha, three application times (before, at and after planting) and two N sources (LAN and urea) plus two controls (0 kg N\/ha). Treatments were arrangement in a factorial combination and a randomized block design with two replications. Applications were either, three weeks before, at or after planting, 10 to 15 cm from the row, at a depth of 10 cm, manually by hand. Except for the control, 20 kg N\/ha of each N rate was applied in the form of LAN together with 30 kg P\/ha (Triple Superphosphate 20%) and 30 kg K\/ha (Potassium Chloride) 5 cm away and 5 cm deeper than the seed with a specialized planter at planting. The maize cultivar PANNAR 6479 was planted at row widths of 1.5 m on 18\/12\/97, 23\/11\/98 and 5\/12\/99 to effective plant densities of 26514, 27083 en 25069 plants\/ha respectively for the three seasons. Only results from the last season\u2019s planting were selected due to a particular interest in effects of a dry spell that occurred after planting. Treatment effects over seasons have been reported previously (Adriaanse 2012a, Adriaanse 2012b).\r\n\r\nRainfall<\/strong>\r\nRainfall distribution differences between seasons are presented in Table 1. Total rain for the growing period of the first season (1997\/98) was the lowest followed by the second season (1998\/99) and then highest for the third season (1999\/00). The first effective rain did however come much later after planting for the last season compared to the previous seasons. In addition the quantity of first effective rain, maximum rain within 30 days after planting and total rainfall for a 30 day period after planting were much lower for the last season compared to the first two seasons. Only results from the last season were selected for further discussion.\r\n\r\n[caption id=\"attachment_1392\" align=\"aligncenter\" width=\"820\"]\"\"<\/a> Table 1: Rainfall distribution differences between seasons( ARC-GCI, Research Report, 2000).[\/caption]\r\n\r\nResults and discussion<\/strong>\r\n\r\nTiming of N-applications<\/strong>\r\nThe application of both N-sources 3 weeks after planting was most effective followed by applications before planting and then followed by applications at planting which was much less effective (Figure 1). This trend was similar to responses over seasons, as was previously reported (Adriaanse, 2012a; Adriaanse, F. G., 2012b.) except for LAN which performed better when applied at planting than before planting over seasons.\r\nLAN compared to urea for time treatments over N-rates\r\nLAN was more effective than urea over N-rates particularly for applications at planting but also for before and after planting applications (Figure1). A yield difference between LAN and urea of as much as 3.2 ton\/ha for applications at planting was observed (Figure 1). Ammonia toxicity due to the band placement of urea at row widths of 1.5 m, which resulted in high concentrations of urea under very dry conditions, was probably largely responsible for this. A lack of adequate rain after planting would also have resulted in a reduction in vertical spread of urea and thus would have concentrated it even more. Ammonia volatilization from a depth of 10 cm in a sandy soil could also have contributed to this negative result from concentrated urea.\r\n\r\nThe risk of a yield loss due to a dry spell after planting will clearly be significantly reduced when LAN is used in preference to urea (Figure 1). Delaying N-applications until 3 weeks after planting was also significantly better than applying all N at planting for both N-sources (Figure 1). LAN applications, 3 weeks after planting, were also significantly better than urea applications before planting (Figure 1).\r\n\r\n[caption id=\"attachment_1395\" align=\"aligncenter\" width=\"711\"]\"\"<\/a> Figure 1. Yield responses to times of applications for the 1999\/2000 season averaged over N-rates (ARC-GCI, Research Report, 2000).[\/caption]\r\n\r\nLAN compared to urea for N-rates over time of application<\/strong>\r\n\r\nOn average LAN was more effective than urea over time of application (Figure 2). Band placed urea-N applications > 15 kg\/ha (35 minus 20 kg N\/ha in the plant mixture) resulted in much lower yields than for LAN at comparable N-rates (Figure 2). Yield at 155 kg LAN-N\/ha was 3.0 ton\/ha more than with urea at the same N-rate (Figure 2). This difference is mostly ascribed to ammonia toxicity effects and possibly also ammonia volatilization resulting from concentrated urea applications.\r\n\r\n[caption id=\"attachment_1397\" align=\"aligncenter\" width=\"711\"]\"\"<\/a> Figure 2. Yield responses to N-rates averaged over times of application for the 1999\/2000 season. At planting 20 kg N\/ha of each N-rate, except the control was applied as LAN in the plant mixture (ARC-GCI, Research Report, 2000).[\/caption]\r\n\r\nConclusions<\/strong>\r\n