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Fertilizer Inputs (fertilizer + input)
Selected AbstractsConsequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheepGRASS & FORAGE SCIENCE, Issue 2 2004P. Dennis Abstract Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid-Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha,1), sheep stocking densities (12 or 9 ewes ha,1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty-one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands. [source] Differential Regulation of Five Pht1 Phosphate Transporters from Maize (Zea mays L.)PLANT BIOLOGY, Issue 2 2006R. Nagy Abstract: Maize is one of the most important crops in the developing world, where adverse soil conditions and low fertilizer input are the two main constraints for stable food supply. Understanding the molecular and biochemical mechanisms involved in nutrient uptake is expected to support the development of future breeding strategies aimed at improving maize productivity on infertile soils. Phosphorus is the least mobile macronutrient in the soils and it is often limiting plant growth. In this work, five genes encoding Pht1 phosphate transporters which contribute to phosphate uptake and allocation in maize were identified. In phosphate-starved plants, transcripts of most of the five transporters were present in roots and leaves. Independent of the phosphate supply, expression of two genes was predominant in pollen or in roots colonized by symbiotic mycorrhizal fungi, respectively. Interestingly, high transcript levels of the mycorrhiza-inducible gene were also detectable in leaves of phosphate-starved plants. Thus, differential expression of Pht1 phosphate transporters in maize suggests involvement of the encoded proteins in diverse processes, including phosphate uptake from soil and transport at the symbiotic interface in mycorrhizas, phosphate (re)translocation in the shoot, and phosphate uptake during pollen tube growth. [source] Amino acid 15N in long-term bare fallow soils: influence of annual N fertilizer and manure applicationsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2008R. Bol Summary Long-term dynamics of amino acids (AAs), from a bare fallow soil experiment (established in 1928 at INRA-Versailles, France), were examined in unamended control (Con) plots and plots treated with ammonium sulphate (Amsul), ammonium nitrate (Amnit), sodium nitrate (Nanit) or with animal manure (Man). Topsoil (0,25 cm) from 1929, 1963 and 1997 was analysed for C, N and 15N content and distribution of 18 amino acids recovered after acid hydrolysis with 6 m HCl. With time, soil N, C and AA content were reduced in Con, Amsul, Amnit and Nanit, but increased in Man. However, the absolute N loss was 3,11 times larger in Man than Nanit, Amsul, Amnit and Con, due to the much higher N annual inputs applied to Man. From 1929 to 1997 in Con, Amsul, Amnit and Nanit the whole soil and non-hydrolysable-N pool ,15N increased associated with the loss of N (indicative of Rayleigh 15N/14N fractionation). No ,15N change from 1929 to 1997 was found in the hydrolysable AA-N (HAN) pool. Fertilizer N inputs aided stabilization of soil AA-N, as AA half-life in the mineral N fertilizer treatments increased from 34 years in 1963 to 50 years in 1997. The ,15N values of alanine and leucine reflected both source input and 15N/14N fractionation effects in soils. The ,15N increase of ornithine (,6,) was similar to the whole soil. The ,15N change of phenylalanine in Con (decrease of 7,) was related to its proportional loss since 1929, whereas for Amsul, Amnit, Nanit and Man it was associated with isotope effects caused by the fertilizer inputs. However, the soil ,15N value of most individual amino acids (IAAs) did not significantly change over nearly 70 years, even with mineral or organic N inputs. We conclude for these bare fallow systems that: (i) ,15N changes in the whole soil and non-hydrolysable AA pool were solely driven by microbial processes and not by the nature of fertilizer inputs, and (ii) without plant inputs, the ,15N of the HAN pool and (most) IAAs may reflect the influence of plant,soil interactions from the previous (arable cropping) rather than present (fallow) land use on these soil ,15N values. [source] Nonlinear response of N2O flux to incremental fertilizer addition in a continuous maize (Zea mays L.) cropping systemGLOBAL CHANGE BIOLOGY, Issue 10 2005Claire P. McSwiney Abstract The relationship between nitrous oxide (N2O) flux and N availability in agricultural ecosystems is usually assumed to be linear, with the same proportion of nitrogen lost as N2O regardless of input level. We conducted a 3-year, high-resolution N fertilizer response study in southwest Michigan USA to test the hypothesis that N2O fluxes increase mainly in response to N additions that exceed crop N needs. We added urea ammonium nitrate or granular urea at nine levels (0,292 kg N ha,1) to four replicate plots of continuous maize. We measured N2O fluxes and available soil N biweekly following fertilization and grain yields at the end of the growing season. From 2001 to 2003 N2O fluxes were moderately low (ca. 20 g N2O-N ha,1 day,1) at levels of N addition to 101 kg N ha,1, where grain yields were maximized, after which fluxes more than doubled (to >50 g N2O-N ha,1 day,1). This threshold N2O response to N fertilization suggests that agricultural N2O fluxes could be reduced with no or little yield penalty by reducing N fertilizer inputs to levels that just satisfy crop needs. [source] Consequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheepGRASS & FORAGE SCIENCE, Issue 2 2004P. Dennis Abstract Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid-Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha,1), sheep stocking densities (12 or 9 ewes ha,1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty-one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands. [source] | |||||||||||||