Whatawhata Research Centre Research Articles

Improving the economic and environmental performance of a New Zealand hill country farm catchment: 4. Greenhouse gas and carbon stock implications of land management change

ABSTRACT An integrated catchment management project was established at the Whatawhata Research Centre in the late 1990s to study the implications of land use and management change for a typical New Zealand hill country pastoral farm system. The main changes implemented on the 296 ha Mangaotama block in 2001–2002 included production forest plantation (147 ha), indigenous riparian planting (8 ha); intensification of livestock enterprises and spaced-tree planting. The purpose of this study was to estimate the greenhouse gas (GHG) balance for the catchment farm, incorporating recent measurement and modelling over a 100-year period (excl. soil carbon). The changes reduced the GHG intensity of the livestock enterprises from 25 to 15 kg CO2-e kg−1 product and turned the system from a net emission source (c. 1 kt CO2-e y−1) into a long-term net sink (−353 kt CO2-e y−1). This was mainly due to planting of Pinus radiata with high carbon assimilation rates, compared to the smaller areas and slower assimilation rates of indigenous trees (currently 5–17 t CO2-e ha−1y−1). Based on 100-year mean tree carbon stocks, it was estimated that the area of pine forestry required to achieve net zero emissions would be in the order of 36% of the catchment farm.

Trends in soil carbon and nutrients of hill-country pastures receiving different phosphorus fertilizer loadings for 20 years

There are few records of long-term trends in soil C and N in grazed pasture systems but recent measurements have demonstrated unexplained losses on New Zealand lowlands. To determine whether losses were also occurring in hill country pastures, we analyzed archived soil samples collected between 1983 and 2006 from two slope classes (steep and easy) at the Whatawhata Research Centre. Soils were Ultic Hapludand and Typic Haplohumult on the easy slopes (10–20°), and Typic Haplohumult on the steeper slopes (30–40°). Soil samples (0–75 mm) had been collected from paddocks that were fertilized with six different loading rates of P (ranging from 0 to 100 kg P ha−1 year−1 since 1985). This range of P loadings allowed us to determine whether P inputs would regulate trends in soil C and N. While there were significant temporal trends in C and N (P < 0.05), these were not unidirectional and trends were not dependent on P loading rate. On average, soil C initially increased during the first 6 years of the trial at 0.270% C year−1 (1.56 t ha−1 year−1) and 0.156% C year−1 (1.06 t ha−1 year−1) on easy and steep slopes, respectively. Subsequently, there was no significant trend in soil C on the easy slopes but soil C declined at −0.066% year−1 (0.45 t ha−1 year−1) on the steep slopes. Similarly, soil N increased between 1983 and 1989 at 0.025% N year−1 (144 kg ha−1 year−1) and 0.012% N year−1 (82 kg ha−1 year−1) on easy and steep slopes, respectively. Post-1989, small but significant losses of total N were measured on the steep slopes of 0.004% year−1 (27 kg N ha−1 year−1) (P < 0.05) with no trend on the easy slopes. Two potential causal factors for these decadal-scale patterns were identified, operating via changes in primary productivity. These were lower S inputs from 1989 due to a change in fertilizer type, and a series of relatively dry summers during the 1990s. These significant inter-annual trends in soil C and N complicate attempts to measure long-term changes in soil organic matter associated with land use change and management practices. This study has demonstrated the potential error associated with infrequent soil sampling to determine long-term trends in soil C and N; large gains or losses could have been detected at Whatawhata depending on when sampling started and finished. Understanding these long-term trends in soil organic matter dynamics and driving factors requires more long-term sampling trials.

Improving the economic and environmental performance of a New Zealand hill country farm catchment: 2. Forecasting and planning land‐use change

The second phase of a multi‐stakeholder, integrated catchment management project at the Whatawhata Research Centre is described. This project explored land use and management change options to improve the economic and environmental performance of the case study hill land catchment farm. Research observations, decision support models and expert stakeholder knowledge were used to develop and predict the outcome of various scenarios for the key performance indicators identified by the Catchment Management Group (CMG). These scenarios included Pinus radiata plantation forestry, livestock intensification and enterprise change, riparian revegetation, indigenous forest restoration and pastoral land stabilisation with erosion control plantings. The resulting predictions did offer scope for improving both the economic and environmental performance of the case study catchment farm, if the time scale for change was not a constraint. The CMG developed a new land‐use plan in order to meet the diverse economic and environmental goals they had originally identified for a “well managed hill land catchment”. The feasibility of this plan depended on significant capital investment in land use and enterprise change, and the outcomes were likely to take up to 30 years to manifest themselves in the key performance indicators.

Improving the economic and environmental performance of a New Zealand hill country farm catchment: 3. Short‐term outcomes of land‐use change

The third phase of a multi‐stakeholder, integrated catchment management project at the Whatawhata Research Centre is described. Land use and management changes were implemented to improve economic and environmental performance of the Mangaotama case study catchment farm. The major changes included: afforestation of 160 of the 296 ha catchment farm with pine and native trees, riparian management of the entire 20 km of stream network via fencing and/or forestry, restoration of 5 ha of existing native forest, and intensification of the remaining pastoral component to a high fecundity ewe flock and bull beef finishing. Marked improvements were observed in the key environmental and economic performance indicators. In particular, declines in sediment (76%) and phosphorus (62%) loads and faecal coliform (43%) levels were observed, native forest fragments showed early signs of recovery in terms of sapling numbers and vegetative cover, and the pastoral enterprise recorded increased per hectare production of lamb (87%) and beef (170%). There were implementation challenges with the better matching of land use to land capability, but this study demonstrated that significant progress can be made in the short‐term.

Whatawhata Catchment Management Project: the story so far

Changes in land use and management were applied to a 296 ha catchment farm at the Whatawhata Research Centre in 2000-2001 to improve its economic and environmental performance. The area had erosion and weed reversion challenges, poorly performing beef and sheep breeding enterprises, and degraded streams. Changes included conversion of the steepest land to plantation forestry; indigenous forest restoration; intensification of the farming enterprises onto easier terrain with better pasture production; changes in stock type; poplar planting for soil stabilisation; and exclusion of livestock from streams. Significant improvements have followed. The per hectare economic surplus for the pastoral enterprise improved from 30% below industry average to 13% above. The forestry enterprise will further improve economic performance in the long-term. There were reductions in the export of suspended sediment (76%), total phosphorus (62%), and total nitrogen (33%). Water clarity has increased, stream temperature has declined and stream invertebrate indices indicate improvements in the fauna. Keywords: agriculture, forestry, macroinvertebrates, riparian, water quality, nitrogen, phosphorus

Effects of variation in shade level, shade duration and light quality on perennial pastures

Two experiments examining the effect of artificial shade on pasture net herbage accumulation (NHA), botanical composition and soil characteristics were conducted between 1994 and 1999 at Whatawhata Research Centre. Both experiments included a range of shade levels (0–94%) and shade durations (3–12 months per year). Experiment 1 also included a light quality treatment, incorporating a range in the red:far red ratio (0.49–1.00). All three shading factors decreased annual NHA, with the most influential being the level of shade, which accounted for 68% of the variation and reduced NHA by 20–80% compared with open pasture. The second most influential factor was shade duration, which accounted for only 6% of the variation in NHA. Shading also led to changes in pasture botanical composition, most notably a decline in legume content in both experiments. There was no evidence that hairy pasture species (grasses or legumes) had any advantage over glabrous species under shade. At shade levels >60%, herbage nitrogen concentrations were elevated by 0.2 percentage points on a per unit dry weight basis, although reduced pasture NHA under higher shading meant lower demand for soil nitrogen. Potential nitrogen mineralisation measurements also indicated that nitrogen cycling is likely to be reduced under shading.

Long-term performance of white clover cultivars oversown into summer-dry hill country

The performance of three white clover cultivars (Huia, Tahora and Prop) was monitored in summerdry hill country at the Whatawhata Research Centre for 9 years. The cultivars were oversown into three steep north-aspect paddocks in autumn 1990. White clover abundance was measured every spring using line transects, and stolon fragments were sampled to determine the contribution of the cultivars to overall populations by allozyme electrophoresis on three occasions (1991, 1993, and 1994). White clover abundance declined from ~50% in the first year to ~4% in 1999. There were no significant differences in abundance between the three cultivar treatments after year 2. There were significant differences in the contribution of the cultivars to white clover populations after 5 years as follows: Huia 27%, Tahora 33% and Prop 56%. The implications of these results for introducing new white clover genotypes into summer-dry hill country are discussed. Keywords: 'Grasslands Huia', 'Grasslands Tahora', hill country, long-term, 'Prop', summerdry, white clover

Evaluation of a beef growth model for use in beef finishing decisions

A decision support computer program for beef finishing, called BoVision, is described. It is based on biological models of animal and pasture growth, and is designed to assist the user in making strategic and tactical decisions about their beef finishing operation. Examples of its uses are to answer questions regarding profitability of l-year versus 2-year-old cattle policies, the optimum stocking rate, and the profitability of local trade versus prime versus bull beef. BoVision can also be used to evaluate premiums required for out-of-season beef, the economics of nitrogen use and supplementary feeding. It can also be used to perform sensitivity analyses. An important aspect of the program's development process was the involvement of a group of beef finishing farmers. The animal growth and pasture intake models used are presented. This paper backgrounds the program's development, and evaluates its use in predicting Angus steer performance for a trial conducted at Whatawhata Research Centre. Performance for a Friesian bull trial is also evaluated. Implications for BoVision's use on farms are discussed. Keywords: animal growth, beef finishing, computer model

Pre- and post-weaning growth of beef calves reared by cows on one of five lifetime nutrition levels

The hypothesis that currently recommended liveweights for beef cows are too high was tested at Whatawhata Research Centre. Industry claims have been that high levels of reproductive efficiency can be achieved with cows running up to 20% lighter than current targets, and eating proportionately less pasture. We ran 150 Hereford x Friesian cows on 1 of 5 lifetime feeding levels or treatments. Average liveweights of the five treatments ranged from 470 to 390 kg at mating but pregnancy rate was not affected. Calf weaning weight was affected, however (P

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

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.

Group monitoring, a basis for decision making and technology transfer on sheep and beef farms

Group farm monitoring is a team approach to technology transfer involving farmers, consultants and researchers. Biological and financial components of farm production are monitored to provide data for decision making and a knowledge of the farm which is shared among the group.Scientists from the Whatawhata Research Centre (WRC) provide comparative information and relevant technology. Production gains on the monitor farms have been achieved within 3 years and further gains are possible. Group farmers benefit from renewed enthusiasm in farming and an increased interest in new technology. Key success factors are group ownership of decisions and outcomes and the credibility of consultants and scientists who are seen to stand by the technology delivered. MAF Technology consultants initiated farm monitoring in the Northland area and have benefited as have farmers through the WRC contact, which provides a broad spectrum of information from a multi-disciplined research group. Based on the Northland success, group farm monitoring has been accepted as a model for technology transfer throughout New Zealand. Keywords group farm monitoring, information, decision making, technology transfer

Long term effects of withholding phosphate application on North Island hill country: Whatawhata Research Centre

From June 1984 to May 1988 a large-scale grazing trial at Whatawhata Research Centre evaluated the effects of a halt to previous superphosphate fertiliser application on hill country production. Over the 4-years pasture production, pasture species composition, stock grazing days or Olsen P soil fertility status were little affected as a result of halting topdressing. Pasture production declined most on 'easy' ( lo-20° slope) slopes after a halt to fertiliser application. The decline was greatest (lo- 13 %) where previous rates of fertiliser had been high. Total production on 'steep' (30~40° slope) slopes did not decline significantly. However, at soil test (Olsen P) levels of less than 10 the pasture moss and dead matter content increased, indicating a deterioration in pasture quality. Legume content did not decline. Within the range of normal topdressing rates to hill country (O-30 kg P/ha/yr) Olsen P tests did not reflect topdressing differences or any effects of a halt to fertiliser application. At higher topdressing rates (50-100 kg Plhalyr) the effect of continued or discontinued topdressing was reflected predominantly in the O-3 cm soil depth. A halt to previous topdressing significantly reduced available grazing over the final 3 years. This decline reflected the decline in measured pasture production. Keywords Phosphate, fertiliser, hill country, residual effects

Effects of withholding fertiliser on pasture production and phosphate cycling in hill country

A large-scale phosphate (P) fertiliser grazing trial was carried out at Whatawhata Research Centre between 1980 and 1984. The effect of 5 fertiliser rates (10, 20 30, 50 or 100 kg P/ha) on pasture production, plant P uptake, dung P distribution, dung decomposition and Olsen P concentration were monitored on 4 slope groups (campsites, O-10"; easy, 1 I-20"; moderate, 21-30" and steep, 31" +). Soils collected from each slope and fertiliser treatment were used in a pot trial to investigate the size of the plant available P pool. Results can be used to interpret data from field trials where fertiliser has been withheld. Initially, pasture production or Olsen P will change little because the most productive areas of the paddock receive large amounts of dung P which buffer the effect of fertiliser withdrawal. On these areas P is cycled more rapidly than on steep slopes, further buffering the system against P deficiency. Small changes in Olsen P do not reflect the more rapid changes in inorganic P or plant-available P. As inorganic P becomes depleted, plant P uptake decreases. The associated decrease in dung P return and the slower rate of dung decomposition contribute to a slowing of the P cycle. The net effect is less feed and slower regrowth after grazing. Recovering from this state will require not only P fertiliser but also time for high producing pasture species to regenerate. Keywords phosphate cycling, topdressing, fertiliser, pasture production, hill country, dung

Effects of soil characteristics and spring management on the persistence of 'Grasslands Matua' prairie grass

'Grasslands Matua' prairie grass was direct drilled into easy hill county at Whatawhata Research Centre. Establishment was excellent, but persistence was poor in most paddocks after 2 years. Site conditions associated with a range of Matua populations were surveyed. Matua population decline was greatest during spring. Spring soil nitrogen levels were associated with persistence, implying that nitrogen application in late winter may enhance persistence. In a trial to assess the effect of spring management on tillering patterns, seed production and seedling vigour, October closing resulted in the highest seed production, seed vigour and highest tiller density after herbage removal. It is proposed that a springsummer hay making policy will enhance the vigour of the existing population and provide adequate reseeding for new plant recruitment. Keywords Matua, persistence, soil survey, nitrogen, tiller density, closing date

SIMULATED SOIL PROFILES AS A PLANT SCREENING TECHNIQUE

A novel, simple technique for screening plants using simulated hill soil protiles is described. Three large bins were constructed and a soil profile built up in each using layers of hill subsoil and topsoil compacted to field bulk density. 2100 ryegrass plants were transplanted at 5 cm spacing in each ot the three bins. This technique has enabled controlled manipulation of soil fertility, development of simulated pure ward conditions and identification of individual plants. It has been used successfully to screen the hill ryegrass collection held at Whatawhata Research Centre for response to nitrogen and drought. Keywords: hill soils, ryegrass. nitrogen, drought, plant screening, soil profiles