The responses of growing pigs to dietary lysine concentration, as influenced by food intake, sex (intact males and females) and live weight were investigated in a 4 x 2 x 2 x 2 factorial experiment involving 128 Large White pigs. Lysine concentrations were 7, 8, 9 and 10 g/kg air-dry food. The basal wheat-soya bean meal diet (14-0 MJ digestible energy per kg) was offered either ad libitum or on a restricted feeding scale to pigs from 20 to 85 kg live weight. During the 50 to 85 kg growth phase, the effects of proportionately reducing the lysine concentrations by 0-2 were investigated. Performance response was assessed in two ways; by analysis of variance for the 20 to 50, 50 to 85 and 20 to 85 kg phases, and by response surface analyses of data from successive 10-kg weight intervals.An initial analysis of variance indicated that food intake (of pigs fed ad libitum), daily gain and food conversion ratio varied with lysine concentration, but that the responses differed with food intake, sex and phase of growth.Analysis of the response surfaces delineated by lysine level and phase of growth indicated that for males and females with restricted food and males fed ad libitum, maximum daily gain was produced by feeding at least 10 g lysine per kg, declining to about 8 g/kg at 80 kg. With females fed ad libitum, maximum daily gain was obtained by feeding 9-9 g lysine per kg at 20 kg, declining to less than 5-6 g/kg at 75 kg.Carcass characteristics were largely unaffected by lysine concentration.
The effect of nitrogen (N) application level on fruit yield and quality, growth and nutrient uptake ofthe tomato cv. Flora-Dade was investigated in a sand culture experiment. Plants were harvested at regular intervals over a 16-week period and N levels (1.07, 5.36, 10.71 and 32.14 mmol L-1 of N as nitrate) were applied each day in a complete nutrient solution which was formulated to provide a stable and balanced nutrient supply. A response surface model fitted actual growth and nutrient uptake data quite precisely (R2> 0.96) over the range 1-32 mmol L-1 of N. From this model predicted growth and nutrient uptake rates were derived.At final harvest, increases in the level of applied N increased the number of fruit set and increased the dry weight of roots, leaf, stem and fruit. Fresh and dry weight of fruit responded to N up to 32 mmol L-I, whereas vegetative and root dry weight failed to respond beyond 11 mmol L-1 N. The firmest fruit with the highest dry matter content were grown at N levels of 11 and 32 mmol L-1. Fruit with the highest total soluble solids content were grown at N levels of 1 and 32 mmol L-I.Fruit dominated top growth over the last 6 weeks of the growth period, when the maximum predicted growth rate by tops of 151 g plant-' week-I was calculated to occur 10 weeks after transplanting at an N application level of 2 1 mmol L-1. Similar growth rates were predicted over the N range 18-32 mmol L-I, with rates increasing rapidly up to early fruit harvest and remaining high. Predicted nutrient uptake rates followed a similar response to growth rates. The maximum uptake rates (g plant-' week-') were 3.65 N, 6.19 potassium, 0.83 phosphorus, 2.03 calcium and 0.59 magnesium.We conclude that, in order to achieve optimum nutrition and hence maximum growth rates and quality oftomatoes under field conditions, the application of N and K fertilisers should be matched to the high demand which occurs over the fruit growth period.
The responses of growing pigs to dietary lysine concentration, as influenced by food intake, sex (entire male and female) and live weight were investigated in an experiment involving 128 pigs. The basal barley-soya-bean diet (14-2 MJ digestible energy (DE) per kg) was offered either ad libitum or according to a restricted feeding scale to both sexes from 20 to 85 kg live weight. The eight dietary lysine concentrations ranged from 8-0 to 12-2 g/kg during the 20 to 50 kg phase and from 6-4 to 9-8 g/kg during the 50 to 85 kg live-weight phase. Performance was assessed by response-surface analysis based on data from successive 10-kg live-weight intervals. Regression analysis was used to assess the response of carcass lean content after slaughter at 85 kg live weight.Daily gain of females fed ad libitum was curvilinear up to maxima of 0-72 and 0-69 g lysine per MJ DE during the 20 to 50 and 50 to 85 kg growth phases respectively. Daily gain response was small but linear up to the maximum dietary lysine concentration for all other combinations of sex and food intake.The response of carcass lean for males given food at a restricted level was linear up to the maximum dietary lysine concentration. For males given food ad libitum, carcass lean response was curvilinear with maximum lean content attained with 0-73 and 0-59 g lysine per MJ DE during the 20 to 50 and 50 to 85 kg live-weight phases respectively. Carcass lean content of females was not affected by lysine concentration within the range used.
Plants grown at 5 nitrate (N) levels ranging from 2-36 mmol L -1 for lettuce and 2-43 mmol L -1 for zucchini squash and potato were harvested over the growth period to maturity at a minimum of 2 week intervals. Gamma x cubic response surface models fitted actual dry matter growth data quite precisely (R2> 0.98) from which growth and dry matter partitioning could be derived.Total dry matter growth was very responsive to N and maximum growth was predicted to occur at an N level of 14.2 mmol L -1 for lettuce, 18.1 mmol L -1 for zucchini squash and 11.6 mmol L-1 for potato. Growth declined at higher N levels for all species. For zucchini squash, both high and low N levels which reduced growth increased partitioning of dry matter to fruit. For potato, partitioning of dry matter to tubers tended to increase at high levels of N, particularly at maturity. For lettuce, the N level producing the highest dry matter yield partitioned the highest ratio of dry matter to head.The highest fresh yields of zucchini squash fruit, lettuce head and potato tubers were recorded at N levels of 14, 5 and 11 and 7 mmol L -~ respectively. The effect of N on quality followed a similar trend.
Leaf emergence rates (LER, leaves/day) of 17 AAA genome banana cultivars (Musa sp., subgroups Gros Michel, Cavendish, Red/Green-red) were estimated using a model based on mean monthly air temperature (13.3-27.9�C), daylength (10.2-13.8 h day), age of planting (48-1361 days), plant density (1111-2222 mats/ha) and cultivar stature (0.88-4.15 m). The LER model involved the five factors in a multiplicative form and was developed initially for one set of 612 observations on all 17 cultivars at Alstonville, N.S.W. but at one density only. The model indicated that LER increased with increasing temperature up to an optimum of c. 28.5�C. LER increased during plant establishment to a maximum at 64 days, then decreased to a stable value with increasing age. LER increased with increasing daylength, but decreased with increasing stature. The model predicted LER without bias for 16 of the cultivars, but slightly over-predicted LER in winter for the only representative of the Gros Michel subgroup (Highgate).Examination of independent data from South Africa revealed that LER decreased with increasing plant density. After the LER model had been adjusted for this effect, it gave an excellent prediction of LER for 229 observations in 20 additional data subsets from Alstonville, Innisfail (Queensland), Burgershall (South Africa) and Azaguie (Ivory Coast), with LERobs = (1.03 � 0.04) LERpred. - (0.005 � 0.004) and coefficient of determination of 0.71. After pooling all 841 observations into one data set, the coefficients of all five factors of the LER model were re-estimated. There were only minor revisions to the coefficients previously obtained, but LER was predicted with slightly greater precision than in the validation test above.
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