Quirine M. Ketterings

Reducing uncertainty in the use of allometric biomass equations for predicting above-ground tree biomass in mixed secondary forests

Abstract Estimates of forest biomass are needed for tracking changes in C stocks, as well as for other purposes. A common method for estimating forest biomass is through use of allometric equations which relate the biomass of individual trees to easily obtainable non-destructive measurements, such as diameter. A common form is B=aDb for biomass B, diameter D and parameters a and b. Field data collected in Sumatra and compared with previously published data show that the values of a and b vary between sites. This variation is likely to be the major source of uncertainty if biomass estimates are produced using equations that are not calibrated for individual sites. However, calibration by collection of B and D data for each site is unrealistic, requiring destructive measures. Methods of choosing values for a and b are, therefore, proposed that do not require destructive measurements. The parameter b can be estimated from the site-specific relationship between height (H) and diameter, H=kDc as b=2+c. The parameter a can be estimated from the average wood density (ρ) at the site as a=rρ, where r is expected to be relatively stable across sites. The allometric equation proposed is therefore B=rρD2+c.

Phosphorus indices: why we need to take stock of how we are doing.

Many states have invested significant resources to identify components of their Phosphorus (P) Index that reliably estimate the relative risk of P loss and incentivize conservation management. However, differences in management recommendations and manure application guidelines for similar field conditions among state P Indices, coupled with minimal reductions in the extent of P-impaired surface waters and soil test P (STP) levels, led the U.S. Natural Resources Conservation Service (NRCS) to revise the 590 Nutrient Management Standard. In preparation for this revision, NRCS requested that a review of the scientific underpinnings and accuracy of current P Indices be undertaken. They also sought to standardize the interpretation and management implications of P Indices, including establishment of ratings above which P applications should be curtailed. Although some states have initiated STP thresholds above which no application of P is allowed, STP alone cannot define a sites risk of P loss. Phosphorus Indices are intended to account for all of the major factors leading to P loss. A rigorous evaluation of P Indices is needed to determine if they are directionally and magnitudinally correct. Although use of observed P loss data under various management scenarios is ideal, such data are spatially and temporally limited. Alternatively, the use of a locally validated water quality model that has been shown to provide accurate estimates of P loss may be the most expedient option to conduct Index assessments in the short time required by the newly revised 590 Standard.

Spatial variability of soil pH and phosphorus in relation to soil run-off following slash-and-burn land clearing in Sumatra, Indonesia

Slash-and-burn land clearing on sloping land may lead to increased soil run-off following disappearance of the protective vegetative cover. In turn, soil run-off and redeposition affects soil fertility and spatial patterns of fertility parameters in a field. This study seeks to clarify the role of spatial patterns of post-burn dead biomass (necromass) in soil run-off and redeposition and their combined effect on spatial patterns in soil pH and resin-extractable P. The study is carried out on a post-productive rubber (Hevea brasiliensis) agroforest in Sumatra, Indonesia. Soils are classified as Dystric Fluvisols. After slash-and-burn of vegetation, the field was planted with rubber seedlings and rice (Oryza sativa). For comparison the adjacent rubber agroforest site was sampled. Soil run-off is expressed here as the quantity of downward moving soil that passed the specific location of a flow trap. Existing physical soil run-off barriers and crop performance were scored. Despite serious soil run-off from the steeper upper slopes little soil was actually lost because of the slope form of the field, presence of natural soil run-off barriers, and the planted crop. Spatial variability of soil pH decreased at the expense of small-scale, within-strata, variability mainly because of the patchy distribution of soil run-off barriers. Soil run-off, aggravated by slash-and-burn, did not result in development of a clear soil fertility gradient down slope. In areas of high soil run-off potential, clear burns should be avoided because soil run-off barriers like remnants of slash-and-burn and surface litter maintain the soil and its fertility.

Response of the Illinois Soil Nitrogen Test to liquid and composted dairy manure applications in a corn agroecosystem

Dairy manure is important for corn (Zea mays L.) production in New York. Optimizing corn yield while minimizing environmental loss with manure nutrients is often a challenge. A potential tool for improving N management is the Illinois Soil Nitrogen Test (ISNT), which estimates amino sugar N, a pool of potentially mineralizable N for corn uptake. The objectives of this study were to determine (1) the short-term effects of manure applications on ISNT-N, and (2) the longer-term impacts of annual additions of composted and liquid dairy manure on ISNT-N. A 6-wk incubation study showed that NH4-N from manure temporarily (< 2 wk) increased ISNT results. A 4-yr field study was conducted with annual spring applications of two rates of composted dairy manure (45 and 77 Mg ha-1) and two liquid dairy manure rates (63.5 and 180 kL ha-1). Results showed that ISNT-N slightly decreased over time in check plots (no manure or fertilizer additions) and that increases in ISNT-N over time in compost and liquid manure amended ...

CONVERSION OF MODIFIED MORGAN AND MEHLICH-III SOIL TESTS TO MORGAN SOIL TEST VALUES

In several states in the Northeastern U.S., the Morgan or Modified Morgan soil tests are used as the basis for both fertilizer recommendations and P runoff risk indices. However, private laboratories servicing these states typically use the Mehlich-III solution as their basic soil test extractant. To meet Natural Resources Conservation Service standards for nutrient management and to use land grant university research databases to derive recommendations, accurate conversions from Mehlich-III and Modified Morgan to Morgan are needed. A study was conducted in New York to: (i) develop models that convert Mehlich-III P, K, Ca, and Mg soil tests to Morgan equivalents; and (ii) evaluate the impact of the use of these prediction models on agronomic recommendations for corn and the New York P index. Soils from 235 locations (27 different New York soil types) were analyzed for pH, modified Morgan P, and Morgan-and Mehlich-III extractable P, K, Ca, Mg, Fe and Al. Multiple regression analysis was used to derive conversion models that fit the data. The models were validated, and the impact of their use on fertilizer recommendations was assessed using a set of >10,000 independently collected New York soil samples. Morgan and Mehlich-III extractable K, Ca, and Mg were correlated linearly with slopes approaching 1. For P, the best model fit was obtained using pH, Mehlich-III P, Ca, and Al as independent variables (r2 = 0.88). A slightly less reliable prediction was obtained without Al (r2 = 0.82). The use of Morgan equivalents did not alter the percentage of low, medium, high, and very high soils in the New York data set, nor did it affect the P index classification. Recommendations for corn derived from a database with independently collected Mehlich-III soil test data (without Al) were identical to those obtained using measured Morgan values for 57% of all samples. An additional 32% showed <10 kg P2O5 ha−1 difference. Eight percent predicted P applications that were 15–20 kg P2O5 ha−1 larger or smaller, whereas 3% showed deviations >20 P2O5 ha−1. Inclusion of Mehlich-III Al data is expected to improve the accuracy of the recommendations and assessment of the P index. We conclude that conversion equations can be used to derive accurate Morgan equivalents based on pH, Mehlich-III P, Ca, and Al, but the results need to be verified based on land use history.

Managing manure for sustainable livestock production in the Chesapeake Bay Watershed

Manure presents one of the greatest challenges to livestock (dairy and beef cattle, swine, poultry, equine, sheep, llamas, etc.) operations in the Chesapeake Bay Watershed, serving both as resource and liability. The Chesapeake Bay is threatened by excessive nutrient loadings, and, according to the US Environmental Protection Agency (USEPA), manure is the source of 18% of the nitrogen and 27% of the phosphorus entering the Chesapeake Bay annually (figure 1) (Chesapeake Bay Program 2010). Developing economical, practical, and effective manure management options for livestock producers will not only contribute to the restoration of the Chesapeake Bay, but will also provide a model for other areas where water quality and livestock production objectives must be balanced. The 166,000 km2 (64,000 mi2) Chesapeake Bay Watershed is home to 3.2 million animal units (animal unit = 454 kg [1,000 lbs] of livestock) generating roughly 36 million t (40 million tn) of livestock manure per year. In comparison, the 14 million humans who call the Chesapeake Bay Watershed home generate 3.6 million t (4 million tn) of waste annually (Brosch 2010; Blankenship 2005). The livestock manure contains approximately 259,000 t (285,000 tn) of nitrogen and 70,000 t (77,000 tn) of phosphorus. Most manure is…

Measuring And Predicting The Phosphorus Sorption Capacity Of Manure-amended Soils

An accurate measurement of the phosphorus (P) sorption capacity of soils is essential to understanding and managing P losses from manure-amended soils. Total P sorption capacity (PSC) was measured in Wellsboro (coarse-loamy, mixed, active, mesic Typic Fragiudept) and Oquaga (loamy-skeletal, mixed, superactive, mesic Typic Dystrudept) channery silt loam soils with varying histories of dairy (Bos taurus) and poultry (Gallus domesticus) manure addition. Batch isotherm analyses were conducted, from which Langmuir sorption maxima were estimated using two methods. Sorption maxima were used to determine the total PSC. Soils ranged in total P from 1080 to 2580 &mgr;g g−1 for dairy fields and 1654 to 11684 &mgr;g g−1 for poultry fields. The total PSC was poorly related to the total P levels in unamended soils (r2 = 0.42) but increased nonlinearly with total P in poultry and dairy soils (r2 = 0.85). Total PSC was well correlated to a single-point P sorption index in all soils (r2 = 0.74). The most accurate predictions of PSC were obtained using a model based on molar amounts of Mehlich-3 Fe, Al, and Ca (r2 = 0.83). When this model was used to calculate the degree of P saturation (DPS), the comparison of DPS with 0.01 M CaCl2 P showed that at DPS greater than 30%, 0.01 M CaCl2 P increased rapidly. We conclude that Mehlich-3 Fe, Al, and Ca data can be used to predict PSC and DPS across soils with widely varying manure management histories.

Plant and soil elemental status as influenced by multi-year nitrogen and potassium fertilization

Abstract Forage management of perennial grass grown under potassium (K)-limiting soil conditions is not well understood. Our objective was to evaluate the elemental status of shoots and roots of reed canarygrass (Phalaris arundinaceae L.) as well as the soil fertility profile (0–90 cm) after five years of differential nitrogen (N) and K fertilization in a two-cut management system. Three N (0, 112, or 224 kg N ha−1) and three K fertilizer treatments (0, 56, and 112 kg K ha−1) were split-applied to reed canarygrass on a Williamson silt loam (coarse-silty, mixed, active, mesic Typic Fragiudepts) soil type in central New York State. At the Fall harvest in the fifth year, plant samples from low and high K fertilized plots all at the high N fertilization rate were cut at a 10-cm stubble height and sectioned into 10 segments vertically through the canopy. In addition, forage, root and soil samples were taken from all treatments to evaluate the distribution of elements under low soil K availability. Above ground biomass samples were separated into leaf blade, stem plus sheath, and dead tissue, if present. This assessment was repeated at the first cutting in the sixth year. That same year, soil cores were taken to a depth of 90 cm, sectioned into 15 cm increments, and analyzed for soil fertility parameters. Dry matter (DM) yield and proportion of DM yield at first harvest were both significantly increased by N fertilization, but not affected by K fertilization in 2001. Elemental concentrations observed vertically through the plant canopy followed patterns controlled primarily by (leaf blade):(stem + sheath) DM ratio and the difference in concentration between leaf blade and stem + sheath. Five years of N and K fertilization of reed canarygrass resulted in an accumulation of plant available K in the top 15 cm of soil under no N and high K fertilization, while the high N/no K fertilization combination greatly depleted soil K in the top 15 cm. Decline in K availability under high N and no K fertilizer was compensated for by an increase in root biomass, particularly in the surface layer. Except for soil K, N and K fertilization did not have an effect on the availability or distribution over depth of other nutrients in the soil.

Emergence and Performance of Two Invasive Swallowworts (Vincetoxicum spp.) in Contrasting Soil Types and Soil pH

Abstract The alien invasive vines black and pale swallowwort are currently spreading across eastern North America, invading parklands, old fields, restored forest sites, and other natural areas. These plants spread by wind-borne seed and can form dense stands where they become established. Although their current geographic ranges overlap, there is little known overlap locally. Preliminary observations and anecdotal information have associated black swallowwort with low-pH inceptisols and pale swallowwort with high-pH alfisols. We conducted a common garden field experiment repeated over two years and a growth chamber germination experiment to assess whether seedling emergence and performance of these two swallowworts are affected by soil type and/or soil pH. Soil pH was artificially modified. In the common garden experiment, plants of both species grown on the Onondaga County soil type (an alfisol) produced a smaller root mass than on the Orange County soil (an inceptisol). Also, in one of two years more seedlings emerged and plants produced more follicles on the Onondaga County soil. Soil pH did not affect seedling emergence, although plants grown on low pH soils had a smaller root dry mass compared with plants grown on higher pH soils. Soil pH effects on stem length, stem dry mass, and follicle production were inconsistent among years. Species differences were also evident, with more pale swallowwort seedlings emerging than black swallowwort seedlings, whereas black swallowwort plants mostly had greater biomass and fecundity than pale swallowwort plants. In the growth chamber experiment, final percentage seed germination was greater on the Onondaga County soil than on the Orange County soil. The germination speed index as well as the probability to reach 50% germination for black swallowwort was higher on the Onondaga County soil than the Orange County soil, but only at lower pH levels. The germination speed index of pale swallowwort on the Orange County soil was higher than black swallowwort at low, but not high, pH levels. In contrast, black swallowwort had a higher probability of reaching 50% germination than pale swallowwort on the Orange County soil at higher pH levels. Contrary to our expectations, interactions between the two swallowwort species with their associated soil type or with their presumably preferred soil pH were weak, contradictory, or non-existent in both experiments. This suggests that these two species can colonize and grow well in a relatively wide range of soil pH conditions. From a management perspective, our results suggest that the current range and local overlap of these two species will continue to increase and that early detection rapid response (EDRR) programs should be established in susceptible regions not yet colonized by these two invasive vines. Nomenclature: Black (or Louises) swallowwort, Vincetoxicum nigrum (L.) Moench, syn. Cynanchum louiseae Kartesz & Gandhi, Pale (or European) swallowwort, Vincetoxicum rossicum (Kleopow) Barbar., syn. Cynanchum rossicum (Kleopow) Borhidi Management Implications: Black swallowwort (BSW) and pale swallowwort (PSW) have become an invasive weed problem in northeastern North America. Currently, there is little overlap at specific field sites of the two species. Anecdotal information has associated BSW with low-pH soils and PSW with high-pH soils. Using both a common garden field experiment and growth chamber study, we assessed whether seedling emergence and performance of these two swallowworts were affected by soil type and/or soil pH. We found that seedling emergence of BSW and PSW was generally not affected by varying levels of soil pH, although soil type could influence germination rates. Apart from root mass size, the effect of soil pH or soil type on subsequent growth, survival and reproduction of first-year plants was variable. There were more consistent differences between species, across soil type or pH range, with more PSW seedlings emerging than BSW seedlings, whereas BSW plants mostly grew larger and reproduced to a greater extent than PSW plants. Based on our findings in this study, it appears that these two species can colonize and grow well in a relatively wide range of soil pH conditions. From a management perspective, our results suggest that the current range and local overlap of these two species will continue to increase and that early detection rapid response (EDRR) programs should be established in susceptible regions not yet colonized by these two invasive vines.

Past and future phosphorus balances for agricultural cropland in New York State

New York State has a large dairy industry resulting in considerable amounts of manure being applied to cropland. Cropland phosphorus (P) balances (manure and fertilizer P minus crop P removal) combined with soil P assessments are illustrative of both challenges and opportunities for long-term sustainability of cropland management at the farm, county, and state scales. Our objectives were to (1) estimate state, regional, and county-level cropland P balances for NY in 2002, (2) evaluate P-balance trends over time (1987, 1992, 1997, and 2002), and (3) quantify the impact of improved herd nutrition and reduced fertilizer use on cropland P balances. Cropland P balances were derived from animal and cropland data from the Census of Agriculture and New York Agricultural Statistics Annual Bulletins and annual farm-use fertilizer sales data. In 2002, cropland P inputs were estimated at 12.7 and 20.9 million kg (28.1 and 46.1 million lb) of P for fertilizer and manure, respectively. Of the manure P, 69% originated from dairy cows. Crop P removal was 21.1 million kg (46.5 million lb), resulting in an overall P balance of +12.5 million kg (+27.6 million lb) or +8.0 kg P ha-1 (+7.2 lb P ac-1), a considerable improvement over 1987 when the statewide P balance was 24.4 million kg (+53.7 million lb) or 15.4 kg P ha-1 (+13.8 lb P ac-1). Without taking into account recent improvements in dairy herd nutrition (i.e., assuming a P excretion of 28 kg cow-1 [62 lb cow-1] per production period), the ratios of P in manure to P in crops were 1.10, 1.12, 1.00, and 0.99, for 1987, 1992, 1997, and 2002, respectively. Thus, the decrease in P balance from 1987 to 2002 reflected reduced fertilizer P use. When improvements in dairy nutrition were taken into account (a decrease in P excretion of dairy cows from 28 to 18 kg cow-1 [62 to 40 lb cow-1] per production period), the 2002 statewide P balance decreased from +8.0 to +4.8 kg ha-1 (+7.2 to +4.3 lb ac-1). This additional reduction illustrates the impact of precision feeding on overall cropland P balances. With a P excretion of 18 kg cow-1 (40 lb cow-1) per production period, increased yields in 2006 (reflected in crop P removal of 23,255 versus 21,104 Mg [25,639 versus 23,268 tn] in 2002) and reduced P fertilizer sales (10,508 versus 12,725 Mg [11,586 versus 14,030 tn] in 2002), the estimated P balance for 2006 amounted to +1.7 kg ha-1 (+1.5 lb ac-1). These assessments illustrate (1) the importance of precision feeding and cropland fertility management for the long-term sustainability of the dairy sector, and (2) the progress made through enhanced agricultural environmental management in New York.