Soil carbon sequestration in grazing systems : managing expectations

The inputs of C.M.G., M.H., and P.S. contribute to the project DEVIL [NE/M021327/1]. The input of P.S. also contributes to the following projects: U-GRASS [NE/M016900/1] and Soils-R-GRREAT [NE/P019455/1]. We thank the Centre of Organic Production and Consumption (EPOK) at the Swedish University of Agricultural Sciences for funding E.R.’s part of the research.Peer reviewedPostprin

Effect of different cleaning procedures on water use and bacterial levels in weaner pig pens

peer reviewedPork is one of the most globally eaten meats and the pig production chain contributes significantly to the water footprint of livestock production. However, very little knowledge is available about the on-farm factors that influence freshwater use in the pig production chain. An experiment was conducted to quantify the effect of three different washing treatments on freshwater use, bacterial levels [(total bacterial counts; TBC), Enterobacteriaceae and Staphylococcus] and cleaning time in washing of pens for weaning pigs. Three weaner rooms were selected with each room having 10 pens and a capacity to hold up to 14 pigs each. Pigs were weaned and kept in the pens for 7 weeks. Finally, the pens were cleaned before the next batch of pigs moved in. The washing treatments used were power washing and disinfection (WASH); presoaking followed by power washing and disinfection (SOAK), and presoaking followed by detergent, power washing and disinfection (SOAK + DETER). A water meter was used to collect water use data and swab samples were taken to determine the bacterial levels. The results showed that there was no overall effect of washing treatments on water use. However, there was an effect of treatment on the washing time (p<0.01) with SOAK and SOAK+DETER reducing the washing time per pen by 2.3 minutes (14%) and 4.2 minutes (27%) compared to WASH. Nonetheless, there was an effect of sampling time (before or after washing) (p<0.001) on the levels of TBC and Staphylococcus, but no effect was seen on Enterobacteriaceae levels. Thus, the washing treatments used in this study had no effect on the water use of the pork production chain. Although there was no difference in both water use and bacterial load, from a producer perspective, presoaking and detergent use can save time and labour costs, so this would be the preferred option

Manure as waste and food as feed : Environmental challenges on Chinese dairy farms

Rapid intensification and decoupling of animal and crop production have contributed to high nutrient losses to the environment from Chinese dairy farms and increasing food–feed competition. This study therefore aimed to understand nutrient management and food–feed competition on Chinese dairy farms. We used bottom-up data from a farm survey amongst 48 dairy farms in Henan, north-central China, between October and December 2020. Herd sizes ranged from 115 to 4289 heads, and 52% of the farms had no cropland or grassland. Farm characteristics were determined to quantify nitrogen and phosphorus flows on dairy farms. Subsequently, nutrient use efficiencies and human-edible protein conversion ratios (HePCR) were calculated and compared amongst farm typologies. We found that Chinese dairy farms largely rely on imported feed and are decoupled from crop production. On-farm croplands play a minor role in feed supply but are overloaded with cattle manure. Average nitrogen and phosphorus use efficiencies at farm level were 20% and 27%, respectively. The HePCR varied from 1.0 to 3.5, with an average of 2.3, indicating that food–feed competition commonly occurs. Farms with higher milk yields and moderate concentrate use performed better in nutrient use efficiencies and HePCR. This inefficient utilisation of nutrients highlights the urgency for developing farm-level guidelines of nutrient management that acknowledge farm differences. Our findings provide insights from both manure- and feed-management perspectives, which could help policy makers to support dairy farms to become more environmentally friendly and contribute to a circular food system

Reducing greenhouse gas emissions of New Zealand beef through better integration of dairy and beef production

Integrating dairy and beef production offers opportunities to reduce greenhouse gas (GHG) emissions of beef production, which is dominated by emissions related to maintenance of the breeding cow. This study aims to quantify the GHG reduction potential of the New Zealand (NZ) beef sector when replacing beef breeding cows and their calves with dairy beef animals. To this end, we combined a cattle herd model of NZ beef and dairy production with GHG emission calculations of beef production. We computed GHG emissions (to farm-gate stage) of the current amount of beef produced, while increasing the number of dairy beef calves at the expense of the number of suckler-beef calves. GHG emissions were 29% lower per kg carcass weight for dairy beef animals compared to suckler-beef animals. The average emission intensity decreased from 21.3 to 16.7 kg CO2e per kg carcass weight (−22%) as the number of suckler-beef animals declined to zero and dairy beef animals increased. Integrating dairy and beef production would enable the NZ beef sector to reduce annual GHG emissions by nearly 2000 kt CO2e (i.e. 22% of the total sector's emissions), while the dairy sector would improve their social licence to operate by reducing the number of surplus dairy calves slaughtered from 4-days old

Predicting nutrient excretion from dairy cows on smallholder farms in Indonesia using readily available farm data

Objective: This study was conducted to provide models to accurately predict nitrogen (N) and phosphorus (P) excretion of dairy cows on smallholder farms in Indonesia based on readily available farm data. Methods: The generic model in this study is based on the principles of the Lucas equation, describing the relation between dry matter intake (DMI) and faecal N excretion to predict the quantity of faecal N (QFN). Excretion of urinary N and faecal P were calculated based on National Research Council recommendations for dairy cows. A farm survey was conducted to collect input parameters for the models. The data set was used to calibrate the model to predict QFN for the specific case. The model was validated by comparing the predicted quantity of faecal N with the actual quantity of faecal N (QFNACT) based on measurements, and the calibrated model was compared to the Lucas equation. The models were used to predict N and P excretion of all 144 dairy cows in the data set. Results: Our estimate of true N digestibility equalled the standard value of 92% in the original Lucas equation, whereas our estimate of metabolic faecal N was –0.60 g/100 g DMI, with the standard value being –0.61 g/100 g DMI. Results of the model validation showed that the R2 was 0.63, the MAE was 15 g/animal/d (17% from QFNACT), and the RMSE was 20 g/animal/d (22% from QFNACT). We predicted that the total N excretion of dairy cows in Indonesia was on average 197 g/animal/d, whereas P excretion was on average 56 g/animal/d. Conclusion: The proposed models can be used with reasonable accuracy to predict N and P excretion of dairy cattle on smallholder farms in Indonesia, which can contribute to improving manure management and reduce environmental issues related to nutrient losses.</p

Freshwater use in livestock production—To be used for food crops or livestock feed?

Current approaches to estimate freshwater use in livestock production systems generally fail to consider the competition for water resources with alternative uses, such as production of food crops food or other ecosystem services. This article presents a new method to account for the competition for freshwater use between food crops and animal feed, while assessing freshwater use in livestock production systems. The developed water use ratio (WUR) is defined as the maximum amount of human digestible protein (HDP) derived from food crops from the consumptive water use (CWU) appropriated to produce 1kg of animal-source food (ASF) over the amount of HDP in that 1kg of ASF. The CWU for livestock production is first categorized according to the land over which it is consumed, based on the suitability of that land to produce food crops. Then, the method assesses food-feed competition by determining the amount of HDP that could have been produced from food crops, using the same CWU currently used to produce ASF. The method enables identification of livestock production systems that contribute to global food supply without competing significantly over water resources with food production, based on their CWU. Three beef production systems in Uruguay are used to illustrate the method. During the backgrounding and the finishing stages, which are analyzed in this study, cattle can be kept on natural pasture (NP), seeded pasture (SP) or in feedlots (FL). The following three systems were analysed: i) NP-NP, ii) SP-SP and iii) SP-FL. Results show that the NP-NP system uses the largest amount of water per kg of beef output. However, results also show that the SP-SP and SP-FL systems can potentially produce more HDP by growing food crops than by producing beef. Based on the traditional measure for water productivity, i.e. the quantity of CWU per kilo of beef produced, we would conclude that the NP-NP system is least efficient, whereas based on the WUR the NP-NP system is the only system producing HDP more efficiently than food crops. Sustainable intensification not only implies improving agriculture and livestock productivity per unit of resource used, but also improving the number of human beings nourished. Results from this study illustrate the importance of considering competition and trade-offs with other uses when evaluating water use efficiency of livestock systems to promote sustainable intensification

Yields and Nitrogen Dynamics in Ley-Arable Systems— Comparing Different Approaches in the APSIM Model

Nitrogen (N) dynamics in ley-arable cropping systems require better understanding in order to assess the potential of such systems to contribute to improved productivity and reduced nutrient losses in crop production. Large inputs of organic matter after termination of the ley phase result in increased mineralization and N availability to subsequent crops. The description and quan-tification of this residual N effect in ley-arable systems remains a major scientific challenge due to its variability and many influencing factors. Simulation modeling could contribute to improved understanding of N dynamics in ley-arable systems. The aim of this study was to evaluate the robust-ness of the Agricultural Production Systems Simulator (APSIM) to predict biomass yield, N yield, and N leaching of different forage maize systems in northwest Europe, while using two different approaches to predict the residual N effect. The evaluation was based on three field experiments covering plant phenology, biomass, N yield, and N leaching over several years. Model adjustments were necessary to describe mineralization of organic matter and release of N after ploughing of the grass leys. For this purpose, three scenarios were investigated by accounting for either (1) above-ground grass residues; (2) above-and belowground grass residues, both with the generic turnover approach in the model; or (3) N release depending on the carbon-to-N ratio of the residue compiled in a simple mineralization model (SMM). The results showed that APSIM-simulated biomass and N yield of maize were reasonable to poor across the different systems and sites, regardless of using the residue-related approach. The SMM performed more accurately compared to the generic turnover approach in predicting N leaching in a maize following a grass-clover ley. However, for all scenarios, APSIM had difficulties to predict a delay of N leaching observed in the experimental data after a pure ryegrass ley. In conclusion, the process description in APSIM related to organic matter mineralization in ley-arable systems under northwest European pedo-climatic conditions needs improved accounting of belowground grass residues, while the SMM is of added value to improve N mineralization patterns and leaching after a ley phase

Carbon footprint of five pig diets using three land use change accounting methods

The aim of our study was to estimate the carbon footprint (CFP) of five diets for fattening pigs in Europe, using three land use change accounting methods: (i) reference CFP excluding emissions from land use change (LUC); (ii) CFP taking into account emissions from direct LUC and (iii) CFP including total LUC risk. Total LUC risk comprises all emissions from land use change caused by commercial agriculture worldwide, allocated to products based on their land use. We compared a standard feed composition (STAND) with four alternative diets directed at reducing the CFP: in CROP diet we assumed an improved crop production through 10% increased crop yields or 10% decreased fertilizer use; in EU diet we excluded soybean products and used European grown feed ingredients only; in BY-P diet we maximized the use of by-products from food and bio-energy industry; and in N-LOW diet we limited crude protein content to 13% while adding synthetic amino acids. Our analysis showed that the method chosen to account for LUC has a major impact on the CFP of each diet and, therefore, affects mutual comparison of diets. Based on the reference CFP, CROP diet showed the lowest CFP, i.e. -6% compared to STAND. When accounting for direct LUC, EU diet had the lowest CFP, i.e. -15% compared to STAND, by avoiding soybean products. When accounting for total LUC risk, N-LOW diet had the lowest CFP, i.e. -9% compared to STAND. We discussed that each of the considered land use change accounting methods has specific strengths and limitations. As a result, we proposed two decision rules when formulating low CFP diets, i.e.: (1) avoid direct land use change as much as possible; and (2) within this precondition, minimize carbon footprint including total land use change risk to encourage the formulation of diets that combine a low reference carbon footprint with low land use requirements

Correcting fresh grass allowance for rejected patches due to excreta in intensive grazing systems for dairy cows

Dairy farms with intensive grazing systems combine grazing with supplemental feeding, which can be challenging because an incorrect balance between fresh grass allowance and feed supplementation results in inefficient use of the pasture, lower feed efficiency, and potential decreases in animal production. When estimating fresh grass allowance, we currently do not correct for the formation of rejected patches (RP) surrounding excreta, which can lead to overestimation of the potential fresh grass intake and hampers optimal grazing. In this study, therefore, we aim to quantify the formation of RP in intensive grazing systems and improve the quantification of fresh grass allowance. To do so, we studied 2 grazing systems (i.e., compartmented continuous grazing and strip grazing) that differ in key grazing characteristics, such as pre- and post-grazing heights and period of regrowth. The experiment was performed from April to October in 2016 and 2017 with 60 dairy cows at a fixed stocking rate of 7.5 cows/ha. Average pre-grazing grass height was measured with a rising plate meter. To quantify the formation of RP after grazing, individual grass height measurements were conducted after grazing and classified as RP or not, based on visual assessment. Our analysis showed that the average percentage of grassland covered with RP increased from around 22% at the end of May to around 43% at the end of July/beginning of August, and these percentages do not differ across grazing systems. The percentage of grassland covered with RP should be subtracted from the total grazed area to better estimate true fresh grass allowance.</p