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Featured researches published by J. S. Rowarth.


New Zealand Journal of Agricultural Research | 2010

The effect of biochars on maize (Zea mays) germination

Hf Free; C. R. McGill; J. S. Rowarth; M. J. Hedley

Abstract Biochar made from biosolids, corn stover, eucalyptus, fresh pine or willow pyrolysed at 550°C and incorporated into Manawatu fine sandy loam or Waitarere sand at rates from 0 to 10 t/ha did not significantly affect the germination or early growth (root and coleoptile length, and dry weight) of maize seeds. There were no interactions between type or rate of biochar with soil type. The results suggest that biochar incorporation prior to a maize crop should be investigated as a method of increasing stable soil carbon with the potential for mitigating carbon emissions.


New Zealand Journal of Agricultural Research | 1985

Release of phosphorus from sheep faeces on grazed, hill country pastures

J. S. Rowarth; A. G. Gillingham; R. W. Tillman; J. K. Syers

Abstract The breakdown of sheep faeces enclosed in mesh bags and placed on 3 slopes of varying steepness on grazed hill country was monitored in both winter and summer. Samples had completely decomposed within 28 days in winter, but lasted for over 75 days in summer. The rate of breakdown was most rapid on the flat camp site areas and slowest on steep slopes. The concentration of both total phosphorus (P) and water-extractable P in the dung samples remained relatively constant with time. Thus the major mechanism controlling movement of P from faeces into the soil was the rate of physical breakdown of the dung rather than the leaching of P from the dung sample. This contrasted with laboratory studies which demonstrate a high water-extractable P content in the dung samples at all stages of the trial. There was no detectable increase in water-extractable P levels in soil samples collected from immediately beneath the decomposing dung.


New Zealand Journal of Agricultural Research | 1990

Predicting the fate of fertiliser sulphur in grazed hill country pastures by modelling the transfer and accumulation of soil phosphorus.

S. Saggar; M. J. Hedley; A. G. Gillingham; J. S. Rowarth; S. Richardson; Nanthi Bolan; P. E. H. Gregg

Abstract A nutrient transfer model developed by Saggaret al. (1990) closely predicted the amounts of soil phosphorus (P) (0–150 mm depth) that had accumulated in the soil from fertiliser and excretal inputs in 20 pastoral farmlets grazed by sheep. The 20 farm1ets, located on hill country in the North Island of New Zealand, were grazed by sheep for 8 years (1980–87) with two grazing managements (continuous and rotational). Five rates of single superphosphate (SSP) were applied within each grazing management. The predictions of the transfer model explained 90% of the variations in soil P amounts between farmlets, and 88% of the variations between slope units across all farmlets. However, the model could predict accurately (within 10% error of prediction) the amounts of accumulated soil S in only those farmlets receiving up to 288 kg S/ha during the last 8 years. At higher levels of SSP fertilisation (–288 kg S/ha), the predicted amounts of soil S were up to 40% higher than the measured amounts of soil S. Th...


New Zealand Journal of Agricultural Research | 1988

Effects of season and fertiliser rate on phosphorus concentrations in pasture and sheep faeces in hill country

J. S. Rowarth; A. G. Gillingham; R. W. Tillman; J. K. Syers

Abstract The effects of different rates of superphosphate fertiliser (10, 20, 30, 50, and 100 kg/ha of P) and of slope (0 – 10, 11 – 20, 21 – 30, 31 – 40° and 41° +) on P concentrations in pasture were monitored on a seasonal basis for 3 years in hill country. Faecal P concentrations were also measured. Pasture P decreased with increasing slope. Pasture and faecal P concentrations increased with increasing fertiliser rate; both were highest in winter and spring and lowest in summer. A highly significant relationship (r = 0.94) existed between the P concentration in pasture on offer for grazing within a paddock and P concentration of the faeces deposited subsequently during the grazing period. This close relationship will facilitate attempts to model P return via the grazing animal and to assess the effects on P losses by animal transfer.


New Zealand Journal of Agricultural Research | 1992

Phosphorus balances in grazed, hill-country pastures: The effect of slope and fertiliser input

J. S. Rowarth; R. W. Tillman; A. G. Gillingham; P. E. H. Gregg

Abstract Data from measurements of phosphate (P) pools (plant P uptake, faecal P return,and total P in soil) in a large-scale, hill-country grazing trial were combined to give P balances for different slopes (0–10°, 11–20°, 21–30°, or 31°+) and different rates of P fertiliser addition (10, 20, 30, 50, or 100 kg/ha). The above-ground components of the P cycle indicated a P surplus on 0–10° slopes and a P deficit on all other slopes. Losses from slopes increased with increasing fertiliser addition, but in proportion to increasing plant P uptake so that P loss per stock unit was unaffected. When changes in soil P were considered, the P balances on slopes were found to be in deficit by approximately the amount of fertiliser P that was added annually.


New Zealand Journal of Agricultural Research | 1992

Effect of phosphate fertiliser addition and land slope on soil phosphate fractions

J. S. Rowarth; A. G. Gillingham; R. W. Tillman; J. K. Syers

Abstract A large-scale phosphate (P) fertiliser grazing trial at Whatawhata Research Centre, North Island, New Zealand provided quantitative information on the effect of slope on changes in the forms of P accumulating, or being depleted, in the soil. Changes in the size of P fractions (Olsenextractable, water-extractable, total, inorganic, organic, easily soluble, non-occluded, occluded, and calcium-bound) were monitored on three slope groups (0–10°, 11–20°, and 31–40°) topdressed annually at five different rates of P fertiliser applied as single superphosphate (10, 20, 30, 50, or 100kg P/ha) for 4 years. Olsen P and total and inorganic soil P increased with increasing rate of fertiliser addition and decreased with increasing depth and slope. Non-occluded P was the largest inorganic P fraction and appeared to be involved in active P cycling and P transfer. In contrast, calcium-bound P was less actively involved in P cycling and appeared to accumulate as residue from fertiliser.


New Zealand Journal of Agricultural Research | 2008

Agricultural intensification protects global biodiversity

J. S. Rowarth

Biodiversity—the term that refers to the variety of forms of life found in a particular location and which ranges in complexity from genes to at least phyla according to the location being considered (a study plot, region or the globe, for instance)—is commonly measured as the number of species in the area being considered, and is of intrinsic concern because of human impacts expressed as loss of species (Huston et al. 2003). The major role agriculture plays in biodiversity decline worldwide has been well documented (Millennium Ecosystem Assessment 2005). In New Zealand (barely m entioned in the millennium assessment) there is indisputable evidence that humans have reduced the acreage of native vegetation (to approximately 23% of its former area; mountainous areas are relatively preserved but there is little


New Zealand Journal of Agricultural Research | 2007

Effects of foliar and root applied nitrogen on nitrogen uptake and movement in white clover at low temperature

M. L. Castle; J. R. Crush; J. S. Rowarth

Abstract ‘Grasslands Huia’ white clover plants were grown at a constant root and shoot temperature of 8°C in a controlled environment room. Nitrate or urea labelled with 15N was applied to the foliage, foliage plus the roots, or to the roots only. After 21 days, plants supplied with foliar nitrogen (N) or with N to the foliage plus roots, produced significantly (P < 0.05) more lamina dry weight than plants supplied with N to the roots only. Plants supplied with N to the foliage contained significantly (P < 0.05) more lamina 15N than plants supplied with N to the foliage plus the roots or to the roots only. From 14 days onwards, plants supplied with foliar N, or N to the foliage plus the roots, had significantly (P < 0.05) higher leaf areas than plants supplied with N to the roots only, irrespective of the form of N applied. By 21 days, plants supplied with foliar nitrate or urea had significantly (P < 0.05) higher photosynthesis, transpiration, stomatal conductance rates, and lamina sucrose concentrations, than plants supplied with N to the roots. The experiment demonstrated the importance of N availability as a rate‐limiting factor on starch and sucrose synthesis and, in turn, on foliage growth at low temperatures in white clover.


Journal of Apicultural Research | 1990

Lead Concentration in Some New Zealand Honeys

J. S. Rowarth

SummaryThe concentration of lead in 59 samples of New Zealand honey taken from several enterprises in three localities in the North Island, and from different stages in processing, was analysed. No samples had lead concentrations higher than the legal limit of 2 μgg−1. No difference in lead concentration was found between honeys of the three districts (one of which was a zone of active mineralisation) but lead concentrations were found to be higher in all samples which had been stored in contact with lead solder.


New Zealand Journal of Agricultural Research | 1992

Phosphate balances in grazed, hill-country pasture: Implications for fertiliser recommendations

J. S. Rowarth; P. E. H. Gregg; R. W. Tillman

Abstract The effect of different rates of phosphate (P) fertiliser (10, 20, 30, 50, or 100 kg P/ha) on various P pools was monitored on four slope groups (0–10°, 11–20°, 21–30°, and 31°+) in a large-scale, hill-country grazing trial. The P pools involved were plant P, faecal P, and soil P (inorganic, organic, nonoccluded, occluded, calcium-bound, and Olsen). Plant availability of the soil P pools was investigated in an exhaustive cropping pot trial. Results from these trials were used to test some of the assumptions and predictions within the Computerised Fertiliser Advisory Scheme (CFAS) used by Ministry of Agriculture and Fisheries advisors to make fertiliser recommendations for many New Zealand farmers. Animal losses of P per stock unit were found to be slightly lower than predicted by the CFAS; estimates of soil losses were similar when based on increases in non-available inorganic P. The net effect was a slightly lower P requirement than suggested by the CFAS. Difficulties with making comparisons bet...

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