Optimized multilateral crop trade patterns can effectively mitigate phosphorus imbalance among the involved countries.

Phosphorus imbalance for cropland can greatly influence environmental quality and productivity of agricultural systems. Resolving cropland phosphorus imbalance may be possible with more efficient multilateral crop trade within the involved trading countries; however, the driving mechanisms are unclear. This study calculates phosphorus budgets in China and five central Asian countries and proposes two optimal multilateral crop trade models to mitigate the phosphorus imbalance. Results show that the current trading pattern between China and Central Asia is causing a phosphorus imbalance intensification. Phosphorus surpluses in China and Uzbekistan are 41.7 and 8.9 kg/ha, while Kazakhstan, Kyrgyzstan, Tajikistan, and Turkmenistan exhibit phosphorus deficits with the negative value of -0.7, -1.2, -0.8, and -0.8 kg/ha, respectively. However, under the optimal multilateral crop trade patterns, phosphorus budget of China and Central Asia will become balanced. Phosphorus imbalance intensification for China is reduced to -2525 and -2472 kt under the single- and bilevel-objective-based crop trades. In Kyrgyzstan, it will drop 61.5 % and 50.0 % and change to 321 and 417 kt under the two optimal crop trades. Moreover, changes of phosphorus imbalance mitigations for other central Asian countries range from 11.9 % to 28.2 %. This provides a scientific basis when establishing policies for strengthening optimal multilateral crop trading across the world to promote global phosphorus management.

Optimal phosphorus management strategies to enhance crop productivity and soil phosphorus fertility in rapeseed-rice rotation.

Optimal phosphorus (P) managements can improve the crop yield without reducing soil P supply capacity over the long term. In this study, the rapeseed-rice rotation experiments were conducted to evaluate the effect of five optimal P fertilizer managements, including the addition of RA (rooting agents), PSB (phosphate solubilizing bacteria), CMP (calcium and magnesium phosphate fertilizer), DP1 (starter P) and DP2 (foliar fertilizer) with the reduction of 40% (in the 1st rapeseed season) and 75% (in the 2nd rapeseed season) P fertilizers of farmers' fertilizer practice (FFP) on crop productivity and soil P fertility in low and high P fertility soils. Seed yield, P partial factor productivity, and P recovery efficiency of both cultivars, Shengguang168 (SG168) and Zhongshuang 11 (ZS11), were significantly improved under optimal P managements, and the increase of them in low P fertility soil was more than that in high P fertility soil. Total P surplus was lower under optimal P managements than under FFP in both P fertility soils. The increasing amount of crop yields under optimal P managements for both cultivars was equivalent to that of 16.0-38.3 kg P2O5 hm-2 of P fertilizer application, and the order of the optimal P managements was as follows: RA > PSB > CMP > DP1 > DP2. In addition, the grain yield of rotated rice cultivar Longliangyou1212 (LLY1212) without P supply was not reduced in both fertility soils. Compared with low P fertility soil, yields of SG168, ZS11 and LLY1212 in high P fertility soil increased by 28.1%-71.7%, 28.3%-78.9% and 26.2%-47.2% at the same treatment, respectively. In summary, optimal P managements in the rapeseed season could stabilize the crop yield, promote P use efficiency and the capacity of soil P supply in the rapeseed-rice rotation, especially in low P fertility soil.

Optimizing phosphate fertilizer input to reduce phosphorus loss in rice-oilseed rape rotation.

Identifying the major sources and critical periods of P loss from agricultural fields provides important guidance for reducing P loss. A rice-oilseed rape rotation with no P fertilization (NP, control), medium P fertilization (MP, 90 kg P2O5 ha-1 season-1), and high P fertilization (HP, 180 kg P2O5 ha-1 season-1) was conducted from 2019 to 2021 in the middle Yangtze River Basin. Runoff and leaching P losses were measured simultaneously using runoff event monitoring and a percolation device. Applying P fertilizer increased the P concentration in the field ponding water and percolation water of the rice-oilseed rape rotation. During the rice growing season, total P (TP), dissolved P (DP), and particulate P (PP) concentrations in the field ponding water and percolation water peaked 1 day after P was applied, and then decreased rapidly. After 10 days of fertilization, P concentration in the field ponding water of the MP treatment decreased to a minimum and stabilized, while the HP treatment extended this period to 20 days. The highest P concentration in percolation water was observed at the first sampling during the oilseed rape season, and then it continued to decrease. Inputting P fertilizer increased P loss by 55.0-109.9% compared to the NP treatment, with annual P losses of 0.89-1.10 kg P ha-1, of which runoff loss accounted for 61.7-62.9%. Fertilization and precipitation resulted in varied P loss within and between seasons. Runoff from heavy precipitation during the rice season was the main source of P loss, while PP accounted for 54.7-77.6% of runoff P loss. The strong utilization of soil P by rice resulted in a lower demand for exogenous P fertilizer than oilseed rape. Excessive P input increased the soil P surplus and vertical migration. Therefore, reducing rice season P fertilizer inputs to achieve annual P balance in rice-oilseed rape rotation can effectively reduce soil P surplus and loss while ensuring crop P demand, and the initial 10 d after fertilization in the rice season was a critical period for reducing P runoff loss.

Characteristics and drivers of daily nitrogen and phosphorus losses from rice-rapeseed rotation systems in the middle reaches of the Yangtze River.

Crop production systems involving the use of high rates of fertilizer application caused significant losses of nitrogen (N) and phosphorus (P) to the environment, resulting in air pollution and water body eutrophication. Quantitating N and P losses and its drivers in crop production systems was critical for optimizing water and fertilizer management measures to mitigate the nutrient losses. However, N and P losses estimation remains highly uncertain in the field at event scale. We here quantify daily N and P losses and its drivers (daily N and P water input, N and P uptake, N and P water surplus, water loss, etc.) in rice-rapeseed growing systems by high-frequency field experiments at event scale in Central China. Results revealed that there were significant trade-off relationships between daily uptake and surplus for N and P during the whole growing stages both for rice and rapeseed. Although it was not significantly related in heading to mature stage for rapeseed, synergies between daily input or surplus and loss were found for N. Redundancy analysis revealed that water input and leaching loss contributed most for N and P loss in rice and rapeseed. The nutrient losses in easier stages should be reduced by postponing the base fertilizer and making it in line with the crop uptake. The study enhanced our knowledge of N and P losses mechanism for crop production systems and provided a scientific basis for optimization of water and fertilizer managements and N and P loss estimation models.

Modelling environmental technical efficiency and phosphorus pollution abatement cost in dairy farms.

The dairy sector is an important sector in Northern Ireland being the single largest contributor to its agricultural economy. However, the sector contributes more to soil phosphorus (P) surplus compared to other agricultural sectors. Consequently, the goal of this research is to analyse the environmental technical efficiency of dairy farms making use of a novel parametric hyperbolic distance function approach. The model is able to internalise P surplus as undesirable output in the dairy production process by treating desirable and undesirable outputs asymmetrically. The stochastic production frontier model is analysed simultaneously with an inefficiency model to explain variability in efficiency scores assuming the existence of heteroskedasticity in the idiosyncratic error term. Additionally, we estimated the shadow price and pollution cost ratio of P surplus in dairy farms. This paper contributes to the existing literature as it provides the first attempt to empirically estimate the pollution abatement cost of P surplus in dairy farms. Besides, the hyperbolic environmental technology distance function methodology employed to achieve the study objectives is less restrictive compared to the radial output/input distance function approach employed in previous studies. This allows for the estimation of a more robust environmental efficiency measure and shadow price of P surplus that is consistent with public policy goals that seek to simultaneously reduce pollution and increase production of desirable outputs. Our results showed that the average environmental technical efficiency estimates for dairy farms in Northern Ireland is 0.93 and the shadow price (marginal abatement cost) of P surplus evaluated at the mean is £12.29/kg. Intensification resulting in increased use of concentrates feed was found to be negatively related to environmental technical efficiency. We also found that age of the farmer and share of milk output have a positive relationship with environmental technical efficiency.

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The changing trend of soil available phosphorus (Olsen-P) content in soil and its relationship with soil phosphorus surplus and crop yield are fundamental when making appropriate phosphate fertilizer recommendations. In this paper, the influences of long-term fertilization on crops phosphorus uptake, soil phosphorus surplus, changing trend of soil available phosphorus content and relationships of soil available phosphorus content with soil phosphorus surplus and crop yield were investigated through 34 years (1981-2015) long-term trial in loessial soil region on the Loess Plateau. The experiment had a completely-randomized-block split-plot design in triplicate. Two main-plot treatments were no farmyard manure and farmyard manure (M), and four subplot treatments were CK (no fertilizer), N (application of chemical fertilizer N), NP (application of chemical fertilizer NP) and NPK (balanced application of chemical fertilizer NPK), respectively. The results showed that fertilization treatments and crop types significantly influenced uptake amount of phosphorus and soil phosphorus surplus. Averaged over time from 1981 to 2015, wheat mean phosphorus uptake amounts of CK, N, NP, NPK, M, MN, MNP and MNPK were 8.63, 10.64, 16.22, 16.21, 16.25, 17.83, 20.39 and 20.27 kg·hm-2, while rape phosphorus uptakeamounts of eight treatments were 4.40, 8.38, 15.08, 15.71, 10.52, 11.23, 17.96 and 17.66 kg·hm-2, respectively. The surplus amount of soil phosphorus significantly correlated with the amount of phosphorus applied to soil. When soil phosphorus surplus amount equal zero, wheat and rape phosphorus input amounts were 10.47 kg·hm-2 and 6.97 kg·hm-2, respectively. Soil phosphorus surplus amount significantly influenced the changing trend of available phosphorus content in soil. CK and N treatments had no phosphorus input, and soil available phosphorus content exhibited a declining trend, annually decreased by 0.16 mg·kg-1 and 0.15 mg·kg-1, respectively. In contrast, NP, NPK, M, MN, MNP and MNPK six treatments were applied with phosphate fertilizer every years, and available phosphorus content gradually increased along with the duration of trial, with annual increase by 0.02-0.33 mg·kg-1. Soil available phosphorus content significantly correlated with phosphorus accumulative surplus amount, and the linear models were y=0.012x+9.33 and y=0.009x+11.72 in manure and no manure treatments, respectively. In no manure treatments, wheat yields significantly positively correlated with soil available phosphorus content, however, in manure treatments, their relationships did not reach a significant level. The relationship of wheat grain yield with available phosphorus content could be significantly fitted by piecewise linear model, and available phosphorus agronomy threshold of wheat was 14.99 mg·kg-1. Rape grain yield also increased with increasing soil available phosphorus content, but the relationship was not significant. This indicated when soil available P content is higher than 14.99 mg·kg -1, application of phosphate fertili-zer should be reduced or even avoided for planting wheat in loessial soil region on the Loess Plateau.