Additional Ton Research Articles

The path of carbon in photosynthesis—Back to the future

F ive to ten billion tons of carbon dioxide from fossil-fuel based energy production and from deforestation burnoff are entering the atmosphere annually. Suggested solutions to this massive accumulation include alternate energy sources, energy conservation, massive reforestation and, in the long term, increased use of natural carbon dioxide reservoirs such as the oceans. Relatively neglected in global planning efforts are the opportunities which may lie in the genetic engineering of the two key enzymes in photosynthetic carbon dioxide fixation, phosphoribulokinase (PRK) and ribulosebisphosphate carboxylase/oxygenase (Rubisco). Even the smallest increase in the efficiency of CO 2 fixation by Rubisco would remove significant amounts of CO 2 from the atmosphere. (A 1% increase on a worldwide basis would theoretically fix 1.5.109 additional tons of CO 2 per year. It is estimated that 1.5.1011 tons of CO 2 are sequestered annually by photosynthesis.) Present funding in this area is modest by any standards and it is surprising that a concerted research program to achieve both an understanding and enhancement of the Rubisco reaction has not been implemented nor, perhaps, even seriously considered at a national level. With this in mind, the purpose of this review is to detail the background and research which led to the first isolation and characterization

N2 fixation and its value to soil N increase in lupin, field pea and other legumes in south-eastern Australia

N2 fixation and its potential contribution to increasing soil total N were estimated in field-grown crops of lupin and pea in 21 trials at 10 locations in New South Wales and Victoria, during 1984 to 1987. Chickpea, faba bean and annual medic were included at some sites. Across experiments there were differences in annual rainfall (267 to 646 mm), soil N (0.02 to 0.20%), soil pH (CaCl2,4.3 to 8.0) and sowing date (24 April to 16 June). Most experiments were conducted on acidic (pH < 4.8) red-earth, the others on grey-cracking clay or sandy soil, both of higher pH The differing sites, seasons, and sowing time contributed to variation in legume biomass (2.02 to 14.33 t/ha) and total N (45 to 297 kg N/ha), and the amount of N harvested with grain (8 to 153 kg N/ha), which were related.Lupin fixed an average of 65% of total crop N, and pea 61%, but there was considerable variation about these averages (20 to 97%). Significant differences in % N2 fixation between legumes within sites were few. The amount of N2 fixed averaged 98.5 kg N/ha by lupin and 80.5 kg N/ha by pea, varying 26 to 288 kg N/ha and 16 to 177 kg N/ha, respectively. Variation in proportional and total N2 fixation was associated with biomass, soil mineral N, and sowing date. N2 fixation increased with more biomass and declined with higher soil mineral N, and later sowing (lupin). Each additional tonne of dry matter increased fixed N by c. 20 kg N/ha. Differences in amounts of fixed N between legumes within sites were due primarily to biomass differences.N2fixed by lupin contributed an average of 38.2 kg N/ha to soil N, and by pea, 17.9 kg N/ha. The contribution was variable, -41 to 135 kg N/ha (lupin) and -32 to 96 kg N/ha (pea), and correlated with proportional and total N2 fixation. Positive increase to soil total N occurred when lupin fixed at least 50% of its crop N, and pea 65%. This occurred in most crops. Legumes frequently used less of the available soil N than cereals.

Influence of some sward characteristics on the consumption of irrigated pastures grazed by lactating dairy cattle

AbstractPasture variables measured in eight experiments at Kyabram, Victoria were used to quantify factors influencing the consumption of irrigated pastures grazed by dairy cows. In addition, whether intake prediction equations based on sward characteristics could be developed and applied in the field was also considered.Herbage intake (DMI) was positively related to herbage allowance (HA) in all cases; however, the increase in daily DMI achieved for every additional kg herbage offered to a cow ranged from 015 to 0·35 kg. Herbage intake was also consistently related to residual herbage (RH). For every additional tonne herbage dry matter (DM) ha−1 remaining after grazing, each cow consumed increased daily amounts of herbage ranging from 3·2 to 5·1 kg DM. However, of the other pasture variables, herbage mass (HM), pasture type (PT) and digestibility of the herbage DM on offer (DMD) influenced herbage intake less consistently.When the data from all experiments were included together, DMI was influenced by sward characteristics in the following manner: image where LW = live weight of the cow (kg) and DE = duration of experiment (d).When RH was considered instead of HA, only 61% of the variability in intake was accounted for compared to 80% when HA was considered: image In both of these equations, two variables other than the sward characteristics were significant; these were LW and DE. The significance of these variables in these relationships are discussed together with the possibility of using them for predicting DMI in other environments. However, it is concluded that they do not have general applicability and it is suggested that they may be useful only in the environment in which they were generated.

Effects of pasture type and grazing management in autumn on the performance of dairy cows in late lactation and on subsequent pasture productivity

An experiment at Kyabram, Victoria, studied the effects of pasture allowance on the production of grazing dairy cows in late lactation (autumn). Cows strip-grazed paspalum dominant or ryegrass-white clover perennial pastures for 60 d from March to May. Mean pasture allowances were 23.2, 13.3 or 6.9 kg digestible dry matter/cow.d. Reduced pasture allowance during late lactation reduced milk yield and body condition. This occurred because pasture intake was positively related to pasture allowance. Each additional kilogram of dry matter (DM) eaten produced 0.93 kg milk and 0.045 kg milk fat. Cows grazing ryegrass-white . clover pastures produced more milk and milk products at equivalent DM intakes than did cows grazing paspalum dominant pastures, and they were in better condition. This was due to herbage quality: cows grazing ryegrass-white clover pastures were able to select higher quality diets than could those grazing paspalum dominant pastures. When the results were compared with those from two previous stall-feeding experiments, the marginal efficiencies for milk production in all experiments were not significantly different; an extra 1.19 kg fat corrected milk was produced for each additional kilogram of digestible dry matter of pasture eaten. . The pastures were not grazed from May to September but their growth and quality were measured during this period. The amount of pasture left at drying off influenced the growth and quality of the pastures throughout winter: daily growth declined by 3.31 kg DM/ha between May and July, and by 6 56 kg DM/ha between July and September, as herbage yield at drying off (May) increased by each additional tonne of DM per hectare. Also, the ryegrass-white clover pastures grew more herbage at equivalent DM yields than did the paspalum dominant pastures. The implications of these results for grazing management are discussed.