The Hertz Corporation

About: The Hertz Corporation is a based out in . It is known for research contribution in the topics: Population & Soil water. The organization has 9562 authors who have published 11044 publications receiving 447929 citations. The organization is also known as: Hertz Rental Car & Hertz Rent-a-Car.

The persistence of seeds of 16 weed species over six years in two arable fields

Abstract: Summary Two experiments have investigated the persistence of 16 arable, annual broad-leaved weed species over 6 years in a silty loam and a clay soil. Small plastic beads were included as an ‘inert’ comparison. Seeds were broadcast in October on to plots at the start of the experiment, and these were either tine cultivated or ploughed annually thereafter. Plots were sown with either spring or winter wheat. As far as possible, weed seeding was prevented each year. For some species, the seed decline appeared to be slower on the ploughed plots than on the tined plots and in the winter wheat compared with the spring wheat. Seed decline also tended to be slower on the clay soil at Rothamsted than on the silty loam at Long Ashton. Some species declined rapidly (e.g. Brassica napus, Chrysanthemum segetum, Galium aparine, Galeopsis tetrahit), with annual decline rates in excess of 58%, whereas others declined very little (e.g. Papaver rhoeas decline rate 9%). Most of the other species had decline rates between 20% and 40%. The results are discussed in relation to the development of population dynamics models to predict long-term consequences of alternative weed management strategies.

Diagnosing sulfur deficiency in field-grown oilseed rape (Brassica napus L.) and wheat (Triticum aestivum L.).

Abstract: The effects of increasing sulfur applications on field-grown oilseed rape (Brassica napus L.) and wheat (Triticum aestivum L.) were investigated in 1998 and 1999, and the critical values and efficiency of several diagnostic indicators for S deficiency were determined. Critical values for leaf concentrations of total S, sulfate and glutathione changed over time and were not suitable for diagnosing S deficiency early in the growth season. The N:S ratio was more reliable but involved two analytical measurements. A practical and reliable indicator for S deficiency was the malate:sulfate peak area ratio as measured by ion chromatography, which required only a single analysis and was independent of the time of sampling or calibration of the samples. A malate:sulfate ratio ≤ 1 indicated S sufficiency at the time of sampling, whereas a ratio > 1 suggested S deficiency at the time of sampling. The malate:sulfate ratio was reliable at growth stage 3.6–3.7 (flower stalks extending to first flowers yellow) for oilseed rape and at growth stage 22–25 (main stem and 2–5 tillers) for wheat, which was sufficiently early in the growth season to apply remedial sulfur fertilizer, if necessary.

Entropy and sustainability

Abstract: Summary Soil–plant systems exchange both energy and matter with their surroundings and are consequently open systems thermodynamically. They should therefore tend towards a steady state described by non-equilibrium thermodynamics and characterized by minimum production of entropy. The theory surrounding the principle of minimum entropy production provides a good analogue of the behaviour of natural and agricultural ecosystems subjected to perturbations. Entropy-increasing processes are those that degrade complex, ordered structures of large molecular weight to small molecules such as CO2, NH3 and H2O. Processes such as photosynthesis that build small molecules into larger ones lessen entropy. These ordering processes are permitted by thermodynamic work performed when heat is transferred from the sun. They depend critically on the capacity of the system for self-organization, which is identified with its biological potential. Several of the small molecules are environmentally undesirable in excess. This, together with the theoretical considerations above, suggests that minimum production of entropy should be a criterion of sustainability. It implies that agricultural systems should be allowed to become steady states where possible and that maintaining the biological potential is essential. An ‘audit of small molecules’ is suggested as a way of assessing sustainability.