D. A. Costall

Influence of fertiliser and grazing management on North Island moist hill country

Abstract A grazing trial was conducted on 99 ha of moist, low-fertility hill country near Woodville, New Zealand, during 1975-1981. Treatments were: low fertiliser (125 kg/ha/a superphosphate (9% P, 10% S)) and high fertiliser (average 630 kg/ha/a superphosphate, plus lime) application rates; and 3 grazing managements — rotational grazing by sheep and by cattle, and set stocking by sheep. Some replication was included in the design, 10 self-contained farmlets being used. Over a 6-year period stocking rate was increased from 6.5 to 12.0 and from 8.8 to 16.1 s.u./ha on low and high fertiliser farmlets respectively. Over this period, and also in the 3 previous years, herbage accumulation was measured, using grazing exclosures and a trim technique. November-April rainfall had a large effect on herbage accumulation rate (HAR) causing year-to-year variation of 23% about mean annual herbage accumulation. The high fertiliser treatment grew 9% more herbage than low fertiliser in the first year after differential a...

Influence of fertiliser and grazing management on North Island moist hill country 2. Pasture botanical composition

Abstract A grazing trial was conducted on 99 ha of steep, low fertility hill country in southern Hawkes Bay, during 1975–81. There were 2 fertiliser treatments: low (LF) and high (HF) superphosphate application (plus lime on HF), and 3 grazing managements — rotational grazing by sheep (RGS) or cattle (RGC), and set stocking by sheep (SSS). As part of a larger measurement programme, botanical composition of pastures was monitored over the 6-year period. HF pastures had a greater content of ryegrass (Lolium perenne L.) and legumes than LF pastures, and a smaller content of low fertility tolerant (LFT) grasses (e.g., browntop, Agrostis capillaris L.; sweet vernal, Anthoxanthum odoratum L.) and weed species. Ryegrass content of pasture under the 3 managements was in the order RGC > RGS > SSS. RGC pastures had a smaller content of LFT grasses, and a greater content of legumes than sheep-grazed pastures. SSS pastures were more weedy than those rotationally grazed. Slope and aspect of measurement site also infl...

Nitrogen concentration in the urine of cattle, sheep and deer grazing a common ryegrass/cocksfoot/white clover pasture

Abstract Total nitrogen (N) concentration in the urine of 12- to 18-month old female sheep, cattle and deer grazing a common pasture was measured in the morning, noon and evening for three consecutive days on two separate occasions in spring, and on a single occasion sampling in autumn. Mean (and range) of urine N concentrations for single urinations were 7.9 (1.4–17.8), 4.4 (0.9–13.2) and 4.1 (0.5–16.6) g N kg−1 fresh urine for sheep, cattle and deer, respectively. Wide ranges in urine N concentration were found within days, between days and between animals within the same species. Differences in urine N concentration between the three different species in any one measurement occasion were significant but inconsistent between measurement occasions. The results presented in this study may have implications for the development of process-based models capable of accounting for the spatially heterogeneous return of excretal N in grazed systems.

Riparian protection and on-farm best management practices for restoration of a lowland stream in an intensive dairy farming catchment: a case study.

Abstract Poor water quality (high concentrations of nitrogen (N), phosphorus (P), suspended solids (SS), and faecal bacteria) in Waiokura Stream, southern Taranaki, New Zealand, is attributed to diffuse and point source (PS) inputs from dairy farming. Trend analysis of concentration time‐series data (2001–2008) and annual yields (i.e., stream load divided by catchment area) showed that significant improvements occurring since 2001 may be attributed to changes in farming practices and riparian management. Yields of filterable reactive P, total P and SS declined by 25–40% as a result of increased riparian protection, a reduction in dairy shed effluent (DSE) pond discharges from 8 to 6 with conversion to land irrigation, and a 25% reduction in the average application rate of P fertiliser. Median annual Escherichia coli concentrations declined at a rate of 116 per 100 ml per year, as a result of fewer PS discharges and improved riparian management. Thus, improvements in stream water quality were attributed to adoption of on‐farm best management practices, fewer DSE discharges and riparian management involving permanent livestock exclusion from stream banks and riparian planting to mitigate runoff from pasture. During 2001–06, N fertiliser use increased by 30% and, with a 130% increase in supplementary cattle feed during 2003–08, led to an increase in average milk solids production 1021 to 1262 kg ha−1 during 2001–06 with the increased production likely associated with increased N leaching losses. Total N and nitrate‐N concentrations and yields increased during 2001–07 as a result of the intensification in land use and increased N cycling. Stream invertebrate surveys using the macroinvertebrate community index (MCI) metric showed little improvement in MCI during 2002–07, probably because of the relatively short timeframe of this study and because water temperatures were not a limiting factor for invertebrate communities. The absence of native forest streams in the proximity of Waiokura Stream that might act as sources of sensitive species to recolonise the restored stream should also be considered as a constraint to improvements in biological community structure.

Effects of fertiliser application on nutrient status and organic matter content of hill soils

Abstract Effects of two fertiliser treatments on soil characteristics were measured during 1972–87, within 10 grazed permanent‐pasture “farmlets”, on steep hill country in southern Hawkes Bay, New Zealand. The low fertiliser (LF) treatment received 125 kg ha‐1 superphosphate p.a., and the high fertiliser (HF) an average 625 kg ha‐1 p.a. for 5 years then 375 kg ha‐1 p.a. subsequently. Ground limestone was applied to HF in 1975 and 1979. Grazing pressure was the same across treatments. Soil fertility decreased with increasing slope of measurement site, and aspect had a less marked effect. Phosphorus initially accumulated mainly in inorganic forms, with organic P accumulating at a slower rate similar to that for organic S. Olsen P status reflected P application regime, although the responsiveness was lower than anticipated. Soil pH in the non‐limed LF treatment increased slightly over time, probably as a consequence of the decline in soil organic C. Soil total N (0–75 mm depth) remained constant in LF, but increased by 19 kg ha‐1 yr‐1 in HF soils. Soil carbon decreased in LF and HF by 200 kg C ha‐1 yr‐1 This suggests that soil organic matter may be decreasing in some New Zealand pastoral environments.

Urine distribution and grazing behaviour of female sheep and cattle grazing a steep New Zealand hill pasture

Much of the nitrogen (N) excreted by grazing animals is within highly concentrated urine patches. The N that is not used by plants is likely to be lost through leaching, emitted as N gases or added to the soil organic N pool. The present study used custom-made global positioning system (GPS) and urine sensors on 20 non-lactating ewes and 20 non-lactating beef heifers grazing steep hill country to determine potential critical source areas for N loss to the environment. Bite counters on four sheep and five heifers showed when and where animals were eating. Animals were monitored simultaneously on 0.5 ha adjacent paddocks over 8 days. Sheep and cows urinated a mean (±s.d.) of 21.2 ± 6.1 and 9.0 ± 3.0 times/day, respectively. Eating started soon after sunrise and increased during the day to reach a maximum in the hour before sunset, after which the eating activity of both species was near zero for most of the night, except for a short feeding period at around 0300 hours. The urination frequency of sheep increased as eating activity increased during the day, but this relationship was not seen in heifers. Land classified as easy hill country (≤12°) comprised 31% of the sheep paddock and contained 23% of the urination events. In contrast, although the easy hill country comprised 33% of the cattle paddock, 46% of the urine patches were in this area. Although aerial application of N mitigation products to whole paddocks or farms is uneconomic, the results of the present study suggest that mitigation products could possibly be cost-effectively targeted to easy contoured, cattle-grazed hill country areas accessible by farm vehicle.

Nitrogen leaching from sheep-, cattle- and deer-grazed pastures in the Lake Taupo catchment in New Zealand

A replicated grazing study measuring nitrogen (N) leaching from cattle-, sheep- and deer-grazed pastures was conducted to investigate the impact of different animal species on N leaching in the Lake Taupo catchment in New Zealand. Leaching losses of nitrate N from intensively grazed pastures on a highly porous pumice soil in the catchment averaged 37, 26 and 25 kg N/ha.year for cattle-, sheep- and deer-grazed areas, respectively, over the 3-year study and were not significantly different (P > 0.05). Leaching losses of ammonium N were much lower (3 kg N/ha.year for all three species of grazer; P > 0.05). Amounts of dissolved organic N leached were significantly higher than that of mineral N (nitrate N + ammonium N), and over the 3-year study averaged 44, 43 and 39 kg N/ha.year for cattle-, sheep- and deer-grazed areas, respectively (P > 0.05). On a stock unit equivalence basis (1 stock unit is equivalent to 550 kg DM consumed/year), cattle-grazed areas leached significantly more mineral N than sheep- or deer-grazed areas (5.5, 2.9 and 3.4 g mineral N leached/24 h grazing by 1 stock unit, for cattle, sheep and deer, respectively) (P < 0.001). Likewise, based on the amount of N apparently consumed (estimated by difference in mass of herbage N pre- and post-grazing), cattle-grazed pastures leached more mineral N than sheep- or deer-grazed pastures (123, 75 and 75 g mineral N/kg N apparently consumed for cattle, sheep and deer, respectively) (P < 0.01). This study gives valuable information on mineral N leaching in a high-rainfall environment on this free-draining pumice soil, and provides new data to assist in developing strategies to mitigate mineral N leaching losses from grazed pastures using different animal species.

Influence of fertiliser and grazing management on North Island moist hill country 4. Pasture species abundance

Abstract A grazing trial was conducted on steep, moist, low fertility hill country in the southern Hawkes Bay during 1975–81. There were 2 fertiliser treatments: low (LF) and high (HF) superphosphate application (plus lime on HF), and 3 grazing managements — rotational grazing by sheep (RGS) or cattle (RGC), and set stocking by sheep (SSS). Annual measurements of pasture species abundance (plant unit density and size) were made in each year during 1976–81. Density of plant units was greater in HF than LF (27.8 cf. 25.3 × 103/m2) pastures and, for the 3 different grazing managements, SSS > RGS > RGC (30.1, 25.2, and 17.1 × 103/m2 respectively). In addition, plant density decreased with increasing slope of measurement site, and was influenced by aspect. In most instances, lower plant unit density was compensated for by increases in plant unit size, in accordance with the ‘3/2 thinning law’. This did not occur under RGC because of severe treading damage, and the depression in herbage accumulation rate in th...

Influence of fertiliser and grazing management on North Island moist hill country 3. Performance of introduced and resident legumes

Abstract A grazing trial was conducted on 99 ha of steep, low fertility hill country in southern Hawkes Bay, during 1975–81. There were 2 fertiliser treatments: low (LF) and high (HF) superphosphate application (plus lime on HF), and 3 grazing managements — rotational grazing by sheep (RGS) or cattle (RGC), and set stocking by sheep (SSS). A white clover (Trifolium repens L.) similar to Kent wild white, and annual suckling clover (T. dubium Sibth.) were already present in the pastures in small amounts. ‘Grasslands Huia’ white clover, ‘Grasslands Turoa’ red clover (T. pratense L.), ‘Grasslands Maku’ lotus (Lotus pedunculatus Cav.), and Woogenellup subterranean clover (T. subterraneum L.) were oversown into the pasture in 1974. Huia, Turoa, and Grasslands 4703 lotus were oversown again in 1977. Woogenellup subterranean clover was found to be unsuited to the environment. Lotus plants established, but contributed little to total herbage accumulation. Red clover was most important in RGC pastures. Its contrib...

Field radiometer with canopy pasture probe as a potential tool to estimate and map pasture biomass and mineral components: A case study in the Lake Taupo catchment, New Zealand

Abstract Precision farming requires data on resource status at a very fine, within‐paddock scale which is impractical to collect by traditional sampling methods. This paper demonstrates the potential of a field radiometer in conjunction with a canopy pasture probe (CAPP) and global positioning system (GPS) to predict and map the spatial distribution patterns of herbage biomass and mass of nutrients, such as nitrogen (N), phosphorous (P), potassium (K), and sulphur (S) in hill country grassland. The accuracy of the calibration model using partial least squares (PLS) regression was assessed by using coefficient of determination (R 2) and the ratio of prediction to standard deviation (RPD). Continuum‐removed derivative reflectance (CRDR) data used in a PLS model gave an excellent prediction of the standing masses of N, P, and S (R 2> 0.895, RPD > 3.0). Both first derivative reflectance (FDR) and CRDR datasets gave a good prediction of standing biomass (R 2 > 0.857, RPD > 2.5). Although relatively lower prediction accuracy was shown in standing K, it may still be possible to make a quantitative prediction using CRDR and FDR (RPD > 2.2). The semivariograms parameter “range” of biomass was longer (58.7 m) than the ranges of the other parameters (10.6–17.4 m), suggesting that biomass values influenced neighbouring values of biomass over greater distances than the other pasture parameters (masses of N, P, K, and S).