Verwantskap tussen anorganiese grondstikstof en mielie-opbrengs met beheerde verkeer

[摘要] English: Nitrogen fertilizer recommendations for maize production in South Africa are basedon yield to be achieved. Inorganic soil nitrogen is seldom used. This approach causesdifficulties in the meaningful seasonal adoption in application rates to be made due tovariance in inorganic soil nitrogen due to climatic variations such as too much rain ordrought. Therefore the relationship between inorganic soil nitrogen and inorganic soilnitrogen with maize yield under controlled traffic practices was carried out.Data of fertilizer trials at Viljoenskroon on a Clovelly soil (1993/94 to 1997/98) and atHeidelberg on a Avalon soil (1991/92 to 1997/98) were used to determine therelationship between applied nitrogen and maize yield, applied nitrogen and inorganicsoil nitrogen as well as inorganic soil nitrogen and maize yield. At both localities thenitrogen rates were factorially combined with phosphor rates and replicated threetimes in a roosterontwerp. The grain yield was determined annually at bothlocalities. Soil samples were annually taken from two weeks after nitrogen sidedressing in a 300 mm band over the maize row (intra row samples) and before plant ina 1200 mm band between the maize rows (inter row samples) on each plot at bothlocalities. These samples were analysed to determine the amount of inorganicnitrogen in the row as well as total soil volumes.The relationship between applied nitrogen and grain yield was parabolic, betweenapplied nitrogen and inorganic soil nitrogen quadratic and between inorganic soilnitrogen and grain yield parabolic. These relationships had explained more varianceat Viljoenskroon than at Heidelberg throughout the study. According to the variance,the relationship of soil reaction on nitrogen application predicted by both localitiesover years was reliable. Plant reaction was predicted at by both localities over yearsby the relationship between soil nitrogen in the intra row maize rows and relativeyield. According to this nitrogen application recommendations can be made for theoptimum amount of soil nitrogen in the intra row for a certain relative maize yield.The amount of nitrogen required to raise inorganic nitrogen content of intra row soilto the desirable level was obtained by the use of the regression equation.The general practice for maize production in South Africa is that a third of thenitrogen is band placed at planting and the remainder applied four to six weeks afterplanting as top dressing. The abovementioned information could help the farmer tocalculate the amount of nitrogen that should be applied to adjust inorganic soilnitrogen levels before and/or during a specified season. This approach has theadvantage that where the maize yield varies according to inconsistent rainfall nitrogenapplications may be adjusted. It must be accentuated that this approach puts greaterdemands to farmers, soil annalistic laboratories and fertilizer providers. Over- andunder fertilization should considerable decreased due to this approach. More researchis however needed for exploitation in other ecotypes.

[发布机构] University of the Free State