Changes of heavy metals in soil and wheat grain under long-term environmental impact and fertilization practices in North China

We evaluated the effects of long-term fertilization on heavy metals in soil and wheat grain under no-fertilizer control (CK), nitrogen, phosphorus, and potassium fertilizers (NPK), NPK plus straw (NPKS), and NPK plus manure (NPKM) treatments. Total lead (Pb) significantly increased in the CK over the initial soil. All fertilization treatments increased soil total arsenic (As) than CK, and the NPKM increased total cadmium (Cd), copper (Cu), and zinc (Zn) than NPK. All fertilization treatments increased soil available As and Cd than CK, and the NPKM increased available As and chromium (Cr) than NPK. The NPKS decreased grain As, Cd, Cu, and bran Cr, Zn, and Pb; but the NPKM increased grain Cr, Pb, and bran As, and Cu than NPK. Under current manure fertilization systems, the maximum bearing year of soil for As, Cr, Cd, Cu, Zn, and nickel (Ni) was 1136, 2990, 694, 1530, 910, and 1555 years, respectively.</p

Descriptive statistics for agronomic efficiency (AE), partial factor productivity (PFP) and recovery efficiency (RE) in the optimal treatment (OPT) and farmers’ practices (FP) for maize in different production regions of China.

<p>Error bars represent standard error.</p

Trend in grain yield for optimal management (OPT), farmers’ practice (FP), and control treatment without fertilization (CK) in the past decade across in maize grown regions in China.

<p>Yield data come from experiments collected by our research group from 2003 to 2012, error bars represent standard error.</p

Change in organic C and N concentrations and their C/N ratios in large macroaggregate (LM) fractions of control (CK), chemical fertilizer (NPK), and the combined manure and chemical fertilizer (MNPK, 1.5MNPK) treatments in the top 40 cm of the soil profile.

Values at each soil depth are the mean of three replicates. The horizontal lines denote the least significant difference values at the 0.05 level (LSD0.05) among different treatments at each soil depth. Symbols of aggregate fractions: see Fig 1 footnote.</p

Geographical distribution of the studied locations in the Northeast (NE), North-Central (NC), Northwest (NW), Southwest (SW) and the Middle and Lower Reaches of the Yangtze River (MLYR) of China.

<p>Geographical distribution of the studied locations in the Northeast (NE), North-Central (NC), Northwest (NW), Southwest (SW) and the Middle and Lower Reaches of the Yangtze River (MLYR) of China.</p

DataSheet_1_Effects of chicken manure substitution for mineral nitrogen fertilizer on crop yield and soil fertility in a reduced nitrogen input regime of North-Central China.pdf

Organic manure has been proposed to substitute part of the chemical fertilizers. However, past research was usually conducted in regimes with excessive nitrogen (N) fertilization, which was not conducive to the current national goal of green and sustainable development. Therefore, exploring the potential of organic fertilizer substitution for mineral N fertilizer under regimes with reduced N inputs is important to further utilize organic fertilizer resources and establish sustainable nutrient management recommendations in the winter wheat (Triticum aestivum L.) – summer maize (Zea mays L.) rotation system in North-central China. In this study, a 4-year field experiment was conducted to investigate the effects of different chicken manure substitution ratios on crop yield, N recovery efficiency (REN), soil N and soil organic matter contents, to clarify the optimal organic substitution ratio of N fertilizer under reduced N application (from 540 kg N ha−1 year−1 to 400 kg N ha−1 year−1). Six substitution ratios were assessed: 0%, 20%, 40%, 60%, 80% and 100% under 200 kg N ha−1 per crop season, respectively, plus a control with no N application from chemical fertilizer or chicken manure. Results showed that the highest yield was achieved under the 20% substitution ratio treatment, with 1.1% and 2.3% higher yield than chemical N alone in wheat season and maize seasons, respectively. At the chicken manure substitution ratios of 20% in wheat season and 20%-40% in maize season, the highest REN reached to 31.2% and 26.1%, respectively. Chicken manure application reduced soil residual inorganic N with increasing substitution ratio. All organic substitution treatments increased soil organic matter and total N content. Implementing 20% organic substitution in wheat season and 20%-40% in maize season under the reduced N application regime in the North-central China is therefore recommended in order to achieve high crop yields and REN, improve soil fertility and enhance livestock manure resource utilization.</p

Yield responses to applied N, P, and K for maize in different production regions of China.

<p>^a NE = Northeast; NW = Northwest; NC = North-Central China; SW = Southwest</p><p>^b 95% confidence interval in parentheses.</p><p>Yield responses to applied N, P, and K for maize in different production regions of China.</p

Variation in the indigenous nutrient supply for maize in Northeast (NE), North-Central China (NC), Northwest (NW) and Southwest (SW); INS, IPS, and IKS indicate indigenous N, P, and K nutrients supply, respectively.

<p>Solid and dashed lines indicate median and mean, respectively. The box boundaries indicate the upper and lower quartiles, the whisker caps indicate the 90^th and 10^th percentiles, and the circles indicate the 95^th and 5^th percentiles. Numbers in brackets denote the number of observations.</p

Yield gaps between attainable yield (YA) and farmers’ yield (YF) in experimental plots and 95% confidence interval (CI) in different production regions of China.

<p>^aNE = Northeast; NW = Northwest; NC = North-Central; SW = Southwest</p><p>^bSD = standard deviation</p><p>^c 95% confidence interval in parentheses</p><p>^d IV = inverse variance, is pre-calculated estimate of treatment effect and standard error of estimate</p><p>Yield gaps between attainable yield (YA) and farmers’ yield (YF) in experimental plots and 95% confidence interval (CI) in different production regions of China.</p

Fertilizer rates in control (CK), chemical fertilizer (NPK), and the combination of manure and chemical fertilizer (MNPK, 1.5MNPK) treatments for each crop.

Fertilizer rates in control (CK), chemical fertilizer (NPK), and the combination of manure and chemical fertilizer (MNPK, 1.5MNPK) treatments for each crop.</p