The use of plantain pasture in dairy systems can potentially reduce nitrogen (N) leaching losses via the lower N concentration in the urine (UNc) of cows. Reducing the urinary N load while cows graze pastures can reduce the risk of N leaching losses from urine patches. Research needs to demonstrate that these environmental benefits are not at the expense of milk production and farm profit. Three groups of 20 cows grazed in the following three pasture treatments: (i) plantain, (ii) plantain–clover mix (plantain, red [Trifolium pratense] and white clover), or (iii) ryegrass-white clover (wc) pastures, from spring to autumn for two years. Each year, pasture intake, diet quality, milk production and animal N (milk and urine) excretion were evaluated in spring, summer, and autumn. The cows grazing the plantain and plantain–clover mix pastures produced similar milk solids as cows grazing ryegrass–wc pasture but reduced their UNc during summer and autumn, when compared to those grazing the plantain–clover mix and ryegrass–wc pastures. Plantain reduced urinary N loads onto pastures by a greater number of urine patches with lower urinary N loading rates. The results demonstrate that plantain pastures do not diminish milk solids production from cows, and the lower UNc from summer to autumn could reduce N being lost to the environment.

The increasing number of satellite missions provides vast opportunities for continuous vegetation monitoring, crucial for precision agriculture and environmental sustainability. However, accurately estimating vegetation traits, such as nitrogen concentration (N%), from Landsat 7 (L7), Landsat 8 (L8), and Sentinel-2 (S2) satellite data is challenging due to the diverse sensor configurations and complex atmospheric interactions. To address these limitations, we developed a unified and physically based method that combines a soil–plant–atmosphere radiative transfer (SPART) model with the bottom-of-atmosphere (BOA) spectral bidirectional reflectance distribution function. This approach enables us to assess the effect of rugged terrain, viewing angles, and illumination geometry on the spectral reflectance of multiple sensors. Our methodology involves inverting radiative transfer model variables using numerical optimization to estimate N% and creating a hybrid model. We used Gaussian process regression (GPR) to incorporate the inverted variables into the hybrid model for N% prediction, resulting in a unified approach for N% estimation across different sensors. Our model shows a validation accuracy of 0.35 (RMSE %N), a mean prediction interval width (MPIW) of 0.35, and an R${}^2$ of 0.50, using independent data from multiple sensors collected between 2016 and 2019. Our unified method provides a promising solution for estimating N% in vegetation from L7, L8, and S2 satellite data, overcoming the limitations posed by diverse sensor configurations and complex atmospheric interactions.

Low pasture magnesium (Mg) intakes by grazing dairy and beef cows is a main cause of hypomagnesaemia in these animals soon after calving. Magnesium fertiliser application to pasture can increase pasture mixed‐herbage (hereafter “herbage”) Mg concentration and reduce the risk of this disorder. However, the effectiveness of Mg fertilisers is variable depending on fertiliser type and soil properties. A 32‐month Mg fertiliser field trial was conducted on dairy pasture on an Immature Orthic Pumice Soil (near Taupo, New Zealand; exchangeable Mg 0.4 cmol _c kg ^–1 , pasture Mg 0.13%) to compare the effectiveness of a range of Mg fertilisers in elevating herbage Mg concentration. The fertilisers used were ground serpentine rock, three acidulated serpentine rock products, Epsom salts, and E‐mag (magnesium oxide). All fertilisers were applied at 100 kg Mg ha ^–1 at the start of the trial. The trial also had two treatments where Epsom salts was applied at 25 and 50 kg Mg ha ^–1 and a treatment where serpentine rock was reapplied during the second and third year at 100 kg Mg ha ^–1 . Magnesium fertiliser treatments did not affect pasture dry matter yield significantly at any harvest, however, the effect of treatments on herbage Mg concentration was highly significant ( P < 0.001) at all harvests. The single application of serpentine significantly increased herbage Mg concentration at 10 harvests, with five of these harvests having Mg concentrations ≥ 0.20%, which is generally considered to be the minimum “threshold level” for stock health. In comparison, the Mg concentration in pasture not receiving Mg fertiliser remained below the minimum threshold level throughout the trial. Application of serpentine rock annually further increased herbage Mg concentration and accumulation. The herbage Mg concentrations for this treatment were similar to those of the Epsom salts (50 kg Mg ha ^–1 ) treatment at the majority of the harvests. These results indicate that the annual application of serpentine rock may have potential as an alternative strategy to the application of more soluble Mg sources for raising herbage Mg concentration to levels considered adequate to meet stock health requirements. The more soluble Mg fertilisers—Epsom salts, the two serpentine‐superphosphate products, and an acidulated serpentine rock plus reactive phosphate rock product—had the greatest effect on increasing herbage Mg concentration and accumulation. These treatments increased herbage Mg concentration to ≥0.20% within 3–6 months after application and for the majority of harvests over the rest of the trial period. The effect of E‐mag on herbage Mg concentration was similar to that of serpentine rock during the first year, but the subsequent performance of E‐mag was similar to the more soluble Mg fertilisers.

Research was conducted in the Manawatu region, New Zealand, to investigate the ability of Papakai tephra to remove phosphorus (P) from dairy farm mole and pipe drainage waters. The capacity of this tephra to adsorb P was quantified in the laboratory using a series of column experiments and was further evaluated in a field study. In a column experiment, the P adsorption capabilities of 2 particle size factions (0.25–1, 1–2 mm) of Papakai tephra were compared with that of an Allophanic Soil (Patua soil) known to have high P adsorption properties. The experiment used a synthetic P influent solution (12 mg P/L) and a solution residence time in the columns of c. 35 min. By the end of the experiment, the 0.25–1 mm tephra removed an estimated 2.6 mg P/g tephra at an average P removal efficiency of 86%. The 1–2 mm tephra removed 1.6 mg P/g tephra at an average removal efficiency of 58%. In comparison, the Patua soil removed 3.1 mg P/g soil at a P removal efficiency of 86%. Although, the Patua soil was sieved to 1–2 mm, this size range consisted of aggregates of finer particles, which is likely to have contributed to this material having a higher P adsorbing capacity. A field study was established on a Pallic Soil, under grazed dairy pastures, to compare drainage water P concentrations from standard mole and pipe drainage systems (control) and drainage systems incorporating Papakai tephra. The 2 tephra treatments involved filling mole channels with 1–4 mm tephra (Mole-fill treatment) or filling the trench above intercepting drainage pipes with ‘as received’ tephra (Back-fill treatment). Over an entire winter drainage season, the quantity of total P (TP) lost from the control treatment drainage system was 0.30 kg P/ha. The average TP losses for the Mole-fill and the Back-fill treatments were 45% and 47% lower than the control treatment, respectively.

Two field experiments were conducted in the Gisborne region of New Zealand to assess the effectiveness of four winter green‐manure crops (lupin, mustard/lupin mix, mustard, and annual ryegrass) for improving the short‐term nitrogen (N) availability of soils growing organic sweetcorn (Zea mays). Average soil mineral (0–15 cm) N in the control treatment (bare soil winter fallow) plots, measured at the time of sweetcorn emergence (late November 1997), was 50.4 kg N ha ^‐1 at Site A and 81.3 kg N ha ^–1 at Site B. Compared with the control (bare soil fallow) treatment, soil incorporation of the lupin and mustard/lupin mix treatments significantly increased soil mineral N by 30–45% at both trial sites at sweetcorn emergence. In contrast, the ryegrass treatment reduced soil mineral N levels by 33–43% at both sites. These treatment effects were related to green‐manure crop N concentrations just before soil incorporation. Sweetcorn N accumulation at final harvest was also significantly increased by soil incorporation of the lupin and mustard/lupin mix treatments and significantly reduced by the ryegrass treatment. Average sweetcorn ear yields in the control treatment plots at maturity were 16t ha ^–1 at Site A and 18 t ha ^–1 at Site B. However, ryegrass treatment significantly reduced sweetcorn ear yields by 64% at Site A and 48% at Site B, which was likely to have been caused by the lower soil mineral N levels attributed to soil incorporation of the ryegrass treatment. Although the lupin and mustard/lupin mix treatments increased soil N availability and uptake by sweetcorn, these treatments did not significantly improve sweetcorn ear yield. The lack of yield response was attributed to soil moisture limitations, which occurred in the latter part of the season and were likely to have restricted yield potential.