The effect of nitrogen fertilisation on the growth, yield and quality of swiss chard (Beta vulgaris var. cicla)

[摘要] English: The sustainability of subsistence farming associated with the health of rural communities'necessitated research on Swiss chard as it forms an integral part of food consumed by thepoor in developing countries. Two separate pot experiments were carried out during the2005/06 and 2006/07 seasons in the glasshouse of the Department of Soil, Crop andClimate Sciences at the University of the Free State. The objective of this study was todetermine the effect of nitrogen fertiliser on growth, yield and quality of Swiss chard.The first pot trial was conducted to evaluate the effect of five nitrogen levels (0, 50, 100,200, 400 kg N ha-1) and four application times on the growth, yield and quality of twoSwiss chard cultivars ('Fordhook Giant' and 'Rhubarb'). Two Swiss chard seedlingswere planted per pot, filled with topsoil of the fine sandy loam Bainsvlei form. Twoweeks after planting plants were thinned to one seedling per pot. Different nitrogenlevels were applied to the relevant pots as follows: once every second, fourth, sixth oreighth week. It was only the total dry mass per plant and total nitrogen content per leafof 'Rhubarb' plants that was significant higher than that of 'Fordhook Giant'. The otherparameters measured for the two cultivars did not differ significantly from each other.Nitrogen levels positively influenced the early growth, yield and quality parametersmeasured. It was the highest nitrogen level (400 kg N ha-1) that resulted in the highestnumber of leaves harvested, leaf fresh and dry mass, leaf area and leaf nitrogen content.Nitrogen application times significantly influenced only the early growth of Swiss chardplants and the nitrogen content of leaves. Early plant growth reacted better wherenitrogen was split into three equal applications (T4). The total nitrogen content of Swisschard leaves was significantly higher where nitrogen was split into five equal (T2) orthree equal (T4) applications.In the second pot trial the effect of different nitrogen sources applied at different levelson the growth, yield and quality of Swiss chard cultivars was determined. The responseof Swiss chard plants to nine nitrogen levels (0, 100, 200, 300, 400, 500, 600, 700,800 kg N ha-1) from six different nitrogen sources (ammonium nitrate, potassium nitrate,calcium nitrate, ammonium sulphate, urea ammonium nitrate and urea) were studied.Based on the findings of this study, nitrogen significantly influenced growth, number ofleaves harvested, leaf fresh and dry mass, leaf area and leaf nitrate content of 'FordhookGiant' plants with best results obtained at 800 kg N ha-1. Nitrogen sources did notinfluence either the total number of leaves harvested nor the fresh mass of harvestedSwiss chard leaves. In both cases, ammonium nitrate gave the best results and calciumnitrate the poorest. Urea influenced the leaf area positively followed by urea ammoniumnitrate, with calcium nitrate resulting in the smallest leaf area per plant. Dry mass ofSwiss chard leaves was also significantly higher where urea was used as nitrogen sourcecompared to where calcium nitrate was used. No significant differences amongst theother nitrogen sources. Ammonium nitrate and potassium nitrate significantly stimulatedthe accumulation of nitrate in Swiss chard leaves, whereas the other nitrogen sources didnot play any role in nitrate accumulation in the leaves of Swiss chard.

[发布机构] University of the Free State