Effect of farmyard manure and mineral fertiliser on the growth of maize (Zea mays L.) in a long-term experiment II. Using the hunt-parsons program for plant growth analysis

Abstract

In a long-term continuous maize experiment set up in 1959, the functional method of growth analysis was applied to investigate the effect of various levels of farmyard manure and mineral fertilisation on the growth of maize (Zea mays L.) and on the dynamics of the growth parameters over a 3-year period (2005–2007). The experiment involved two nutrient levels (based on the active agent equivalence principle): Level l: the NPK equivalent of 35 t ha−1 farmyard manure (FYM), applied in the form of FYM, FYM + mineral fertiliser or mineral fertiliser; Level 2: the NPK equivalent of 70 t ha−1 farmyard manure (FYM), applied in the form of FYM, FYM + mineral fertiliser or mineral fertiliser. The computerised growth analysis program elaborated by Hunt and Parsons (1974) was used to describe the effect of FYM and mineral fertiliser and to evaluate the results. This program fits functions to calculate the absolute growth rate (AGR), the relative growth rate (RGR), the net assimilation rate (NAR) and the leaf area ratio (LAR).The Hunt-Parsons program fitted a third-degree function to the dynamics of total dry matter production and second- or third-degree functions to that of the leaf area growth. The highest mean values of AGR were obtained in treatments with the higher level of mineral fertiliser alone or mineral fertiliser + FYM when the weather was favourable (2.05–2.31 g plant−1 day−1), and in treatments with the lower quantity of mineral fertiliser alone or mineral fertiliser + FYM in the case of dry weather (1.73–1.74 g plant−1 day−1). In 2005 and 2006 the absolute growth rate gave a good characterisation of the various fertiliser effects, which exhibited high values with significant differences, while in 2007 lower AGR values were obtained and no fertiliser effects were observed. In the dry year (2007) the maximum values of NAR and LAR were higher in all the treatments than in the wetter years (except at the lower rate of mineral fertiliser alone). In the case of NAR, the results obtained with the functional method of growth analysis, based on function fitting, were easier to interpret than those obtained using the classical method.It was concluded from the results that in long-term experiments the use of the functional method of growth analysis gave a more precise evaluation of the effects of fertiliser treatments and the year on the growth of maize in the vegetative growth stage and on the mean and maximum values of growth parameters.