Phosphorus (P) losses from land-applied manure can contribute to nonpoint source pollution of surface waters. Dietary P levels influence P concentrations in animal manures and may affect P losses from land-applied manure. The objective of this study was to determine the effects of dairy diet P concentration on P losses in runoff from landapplied manure. Manures with P concentrations of 0.48 and 1.28 % P from two dietary P levels were applied to a silt loam soil 25 wet ton/a (36 and 96 lb P/a, respectively). The high P manure was also applied at 9.4 wet ton/a (36 lb P/a) to provide an equivalent P rate as the low P manure. Plots were subjected to simulated rainfall (2.83 in/hr) in June and again in October. Runoff was analyzed for dissolved reactive P (DRP), bioavailable P, total P, and sediment concentration. Natural runoff from the same plots was collected from November through May and analyzed for P as described above. At equivalent manure rates, DRP in June runoff from the high P manure was about 10 times higher (0.30 vs. 2.84 ppm) than the low P manure, and 4 times higher (0.30 vs. 1.18 ppm) when applied at equivalent P rates. Phosphorus concentrations in October runoff and November -May natural runoff were lower (0.02 -1.69 ppm), but treatment effects were the same as for June runoff. These results show that excess P in dairy diets increases the potential for P loss in runoff from land-applied manure. Furthermore, diet P effects on potential losses in runoff from land-applied manure should be considered in P-indexing and nutrient management planning.

Phosphorus losses from land-applied manure can contribute to that the average dairy diet in the USA is supplemented nonpoint source pollution of surface waters. Dietary P forms and levels influence P concentrations in animal manures and may affect P to contain 4.8 g P kg Ϫ1 , while only 3.8 g P kg Ϫ1 is needed losses from land-applied manure. The objective of this study was to for optimum milk production and reproductive effidetermine the effects of dairy diet P concentration on P losses in ciency. This is a 25% over-supplementation of dietary P, runoff from land-applied manure. Dairy manures from two dietary P based on National Research Council standards (Nalevels were applied (24 May 1999) at 56 wet Mg ha Ϫ1 to a silt loam tional Research Council, 1989). Valk et al. (2000) dissoil, to provide 40 and 108 kg P ha Ϫ1 , respectively. The high P diet cussed the possibility of decreasing P in dairy cow diets manure was also applied at 21 wet Mg ha Ϫ1 (40 kg P ha Ϫ1) to provide without negatively affecting performance and reproduca P rate equivalent to the low P diet manure. Plots were subjected tive ability, and cited the work of Brodison et al. (1989) to simulated rainfall (75 mm h Ϫ1) just prior to corn (Zea mays L.) showing that dietary P could be lowered from 6.5 to planting in June and again after harvest in October 1999. Runoff 4.5 g P kg Ϫ1 without consistently influencing milk prowas analyzed for dissolved reactive P (DRP), bioavailable P (BAP), total P (TP), and sediment concentration. Natural runoff from the duction or reproductive performance. One study has same plots was collected from November 1999 through July 2000 and shown that a 40% decrease in dietary P lowered exanalyzed for DRP. At equivalent manure rates, DRP concentration in creted P by 23% (Morse et al., 1992), and another study June runoff from the high P diet manure was ≈10 times higher (2.84 vs. reported that reduced dietary P levels lowered P excre-0.30 mg L Ϫ1) than the low P diet manure, and four times higher (1.18 tion by 30% (Metcalf et al., 1996). vs. 0.30 mg L Ϫ1) when applied at equivalent P rates. Phosphorus Phosphorus excretion in manure depends largely on concentrations in October runoff and November to July natural runoff the level of P intake (Ternouth, 1989; Morse et al., were lower (0.02 to 1.69 mg L Ϫ1), but treatment effects were the same 1992; Metcalf et al., 1996; Khorasani et al., 1997). If P as for the June runoff. These results show that excessive addition of Dairy (Bos taurus) diet P effects on P losses in runoff in no-till corn (Zea mays L.) were determined in a field experi

Our understanding of climatic conditions, and therefore forcing factors, in North America during the past two glacial cycles is limited in part by the scarcity of long, well-dated, continuous paleoclimate records. Here, we present the first, to our knowledge, continuous, millennial-resolution paleoclimate proxy record derived from millimeter-thick pedogenic carbonate clast coatings (pedothems), which are widely distributed in semiarid to arid regions worldwide. Our new multiisotope pedothem record from the Wind River Basin in Wyoming confirms a previously hypothesized period of increased transport of Gulf of Mexico moisture northward into the continental interior from 70,000 to 55,000 years ago based on oxygen and carbon isotopes determined by ion microprobe and uranium isotopes and U-Th dating by laser ablation inductively coupled plasma mass spectrometry. This pronounced meridional moisture transport, which contrasts with the dominant zonal transport of Pacific moisture into the North American interior by westerly winds before and after 70,000–55,000 years ago, may have resulted from a persistent anticyclone developed above the North American ice sheet during Marine Isotope Stage 4. We conclude that pedothems, when analyzed using microanalytical techniques, can provide high-resolution paleoclimate records that may open new avenues into understanding past terrestrial climates in regions where paleoclimate records are not otherwise available. When pedothem paleoclimate records are combined with existing records they will add complimentary soil-based perspectives on paleoclimate conditions.

Soil test phosphorus (STP) measurements are important for predicting crop P needs and for P loss risk assessments. Previous work indicates that the Bray P1 method extracts less P and does not correlate as well with Mehlich 3 or Olsen STP methods in alkaline or highly calcareous soils. This research was conducted to determine if the Bray P1 test is an appropriate method for the eastern red soil (ERS) region of Wisconsin, where pH typically ranges from 7 to 8 and soils are often calcareous. Soil samples (n = 113) from the ERS region and comparison soils (CS) from Iowa and Kansas (n = 38) with high pH and carbonate content were analyzed for P using the Bray P1, Mehlich 3, and Olsen methods and for soil pH and carbonate content. Results indicate that Bray P1 is strongly correlated with Olsen and Mehlich 3 for all samples in ERS regardless of carbonate content (R2 = 0.83 and 0.98, respectively), but only weakly correlated to Olsen and Mehlich 3 for Iowa and Kansas soils with carbonate contents ≥ 5 g kg−1 (R2 = 0.01 and 0.08, respectively). Further investigation indicated that carbonate in CS is calcitic while in ERS it is dolomitic. Because dolomite reacts much more slowly than calcite, Bray P1 is not neutralized in ERS during the 5 min extraction time. For soil with unknown carbonate content, a pH measurement on the Bray P1 filtrate can identify samples where Bray P1 is neutralized and an alternative P extractant should be used.

Phosphorus (P) is often supplied to field crops in organic forms such as manures or biosolids, but P availability and appropriate application rates may differ between sources. An incubation study was conducted using a Ringwood silt loam soil and seven P sources. The P sources were low, medium, and high P manure (feces) from a dairy feeding study, whole manure, fiber manure from a liquid-solid separator, biosolids from a municipal sewage treatment facility, and inorganic P applied as calcium phosphate (CaHPO 4 ). Phosphorus sources were applied at rates of 0, 101, 202, and 404 kg total P ha 21 and incubated at 258C. Five soil samplings were taken at 16-week intervals and analyzed for deionized water extractable P, Mehlich 3, Bray-Kurtz P1, ammonium oxalate extractable P, P saturation, bioavailable P, and anion exchange membrane extractable P. In general, the low P and fiber manures supplied the least available P, CaHPO 4 the most, and medium, high, whole, and biosolids contributed intermediate amounts of P as determined by the soil P tests. The 101 and 202 kg total P ha 21 rates did not differ from each other, but were significantly lower than the 404 kg total P ha 21 rate. Except for fiber at 101 kg total P ha 21 , all treatments significantly increased soil test P compared to the control. The amount of P available did not change over time except at the 404 kg total P ha 21 rate where available P usually increased with time. Correlations among soil P tests indicated significant positive relationships for each test. Bray -Kurtz P1 was most highly correlated to Mehlich 3 ðr 2 ¼ 0:92Þ and least correlated to anion exchange extractable P ðr 2 ¼ 0:13Þ: Bioavailable P and deionized water extractable P were similarly correlated to Bray -Kurtz P1 with relatively high r 2 values of 0.83 and 0.84, respectively. Ammonium oxalate extractable P and P saturation had lower r 2 values (0.78 and 0.74, respectively), but were still positively correlated to Bray -Kurtz P1 and could have useful predictive value. These results indicate P availability in soil varies with the type and composition of the P source. Strong correlations among agronomic and environmental soil P tests suggest that routinely used agronomic tests or the simple DI water extractable P test could be used in place of more time consuming and expensive environmental tests to assess the P status of soils and to determine risks of various fields to release P in runoff.