Anning Zhu

Acid and Alkali Buffer Capacity of Typical Fluvor-Aquic Soil in Huang-Huai-Hai Plain

Soil acid and alkali buffer capacity, as a major indicator for evaluating its vulnerability and resistibility to acidification and alkalization, is an important factor affecting the sustainable agriculture, through knowledge on which soil acidification process can be predicted and modified. In this study, titration curve method was adopted to investigate the pH buffer capacity (pHBC) of fluvor-aquic soil, and separate titration curves were established by adding incremental amounts of either standardized hydrochloric acid (HCl) (0.12 mol L−1) or sodium hydroxide (NaOH) (0.10 mol L−1) to soil suspended in deionized water (soil:solution = 1:5). Soil pH was measured after 7 d resuspension and isothermal equilibrium (T = 25°C). Linear regressions were fitted to the linear portion of each titration curve and the slopes of these lines were derived as the soil pHBC. The results showed that significant correlations between the amounts of adding acid or alkali and each pH change were presented, and titration curve method was feasible for measurement of pHBC on typical fluvor-aquic soil in Huang-Huai-Hai Plain, and the coefficients of determination were higher than the similar researches on acid soil (R2 = 0.96). The slope-derived pHBC of acid and alkali were 158.71 and 25.02 mmol kg−1, respectively. According to the classification of soil buffer systems, the soil tested belongs to the calcium carbonate buffer system, carbonates contribute the most to pHBC, and the contribution of soil organic matter relatively less than it.

Changes in soil organic carbon and aggregate stability after conversion to conservation tillage for seven years in the Huang-Huai-Hai Plain of China

Abstract Soil aggregate stability and organic carbon (OC) are regarded as effective indicators of soil structure and quality. A long-term field experiment was established in 2006 to examine the influence of tillage systems on soil aggregation and OC in a sandy loam soil in the Huang-Huai-Hai Plain of China. The study involved eight treatments: plowing every year with (TS) and without residue (T), plowing every 2 years with (2TS) and without residue (2T), plowing every 4 years with (4TS) and without residue (4T), and no plowing with (NTS) and without residue (NT). In 2013, soil samples were collected at depths of 0–5, 5–10 and 10–20 cm, and separated into three aggregate-size classes: macroaggregates (>250 μm), microaggregates (53–250 μm) and the silt+clay fraction ( microaggregates>silt+clay fraction. In the 0–5 cm soil layer, concentrations of macroaggregate-associated OC in 2TS, 4TS and NTS were 14, 56 and 83% higher than for T, whereas T had the greatest concentration of OC associated with the silt+clay fraction in the 10–20 cm layer. Soil OC concentrations under 4TS and NTS were significantly higher (P

Arbuscular mycorrhizal fungal diversity, root colonization, and soil alkaline phosphatase activity in response to maize-wheat rotation and no-tillage in North China.

Monitoring the effects of no-tillage (NT) in comparison with conventional tillage (CT) on soil microbes could improve our understanding of soil biochemical processes and thus help us to develop sound management strategies. The objective of this study was to compare the species composition and ecological function of soil arbuscular mycorrhizal (AM) fungi during the growth and rotation of crops under NT and CT. From late June 2009 to early June 2010, 32 topsoil (0–15 cm) samples from four individual plots per treatment (CT and NT) were collected at both the jointing and maturation stages of maize (Zea mays L.) and wheat (Triticum aestivum L.) from a long-term experimental field that was established in an Aquic Inceptisol in North China in June 2006. The AM fungal spores were isolated and identified and then used to calculate species diversity indices, including the Shannon- Wiener index (H’), Evenness (E), and Simpson’s index (D). The root mycorrhizal colonization and soil alkaline phosphatase activity were also determined. A total of 34 species of AM fungi within nine genera were recorded. Compared with NT, CT negatively affected the soil AM fungal community at the maize sowing stage, leading to decreases in the average diversity indices (from 2.12, 0.79, and 0.82 to 1.79, 0.72, and 0.74 for H’, E, and D, respectively), root mycorrhizal colonization (from 28% to 20%), soil alkaline phosphatase activity (from 0.24 to 0.19 mg/g/24 h) and available phosphorus concentration (from 17.4 to 10.5 mg/kg) at the maize jointing stage. However, reductions in diversity indices of H’, E, and D were restored to 2.20, 0.81, and 0.84, respectively, at the maize maturation stage. CT should affect the community again at the wheat sowing stage; however, a similar restoration in the species diversity of AM fungi was completed before the wheat jointing stage, and the highest Jaccard index (0.800) for similarity in the species composition of soil AM fungi between CT and NT was recorded at the wheat maturation stage. Our results also demonstrated that NT resulted in the positive protection of the community structure of AM fungi and played an important role in maintaining their functionality especially for maize seedlings.

Application of a high-temporal resolution method to estimate ammonia emissions from farmland

A viable method—open-path tunable diode laser absorption spectroscopy (OPTDL) in conjunction with a backward Lagrangian stochastic (bLS) dispersion model—has been used for micrometeorological monitoring of ammonia fluxes. In this technique, the gas concentration measured with the OPTDL sensor is used to infer the surface emission rate with the aid of dispersion model calculations. On the basis of numerous assessment experiments and field trials, several beneficial strategies for using the OPTDL technique properly to monitor atmospheric NH3 concentrations in the field have been summarized. Theoretically, the location of the concentration measurement can be anywhere in the emission plume, but in practice, the concentration measurement position must be carefully selected to avoid making measurements which are on the periphery of the downwind plume or are affected by obstructions. To obtain accurate estimates, periods with low friction velocity or extreme atmospheric stability, where Monin–Obukhov similarity theory-based relationships are invalid, or unrepresentative estimates due to unsuitable wind direction, should be excluded. A validation experiment showed that there was no significant difference between the ammonia emission rates obtained by the micrometeorological mass balance method and those obtained by the bLS model combined with the OPTDL technique. This study also indicated the potential of the bLS and OPTDL technique for investigation of diurnal emission patterns and environmental influences.

Nitrate accumulation and leaching potential reduced by coupled water and nitrogen management in the Huang-Huai-Hai Plain

Irrigation and nitrogen (N) fertilization in excess of crop requirements are responsible for substantial nitrate accumulation in the soil profile and contamination of groundwater by nitrate leaching during intensive agricultural production. In this on-farm field trial, we compared 16 different water and N treatments on nitrate accumulation and its distribution in the soil profile (0-180cm), nitrate leaching potential, and groundwater nitrate concentration within a summer-maize (Zea mays L.) and winter-wheat (Triticum aestivum L.) rotation system in the Huang-Huai-Hai Plain over five cropping cycles (2006-2010). The results indicated that nitrate remaining in the soil profile after crop harvest and nitrate concentration of soil solutions at two depths (80cm and 180cm) declined with increasing irrigation amounts and increased greatly with increasing N application rates, especially for seasonal N application rates higher than 190kgNha-1. During the experimental period, continuous torrential rainfall was the main cause for nitrate leaching beyond the root zone (180cm), which could pose potential risks for contamination of groundwater. Nitrate concentration of groundwater varied from 0.2 to 2.9mgL-1, which was lower than the limit of 10mgL-1 as the maximum safe level for drinking water. In view of the balance between grain production and environmental consequences, seasonal N application rates of 190kgNha-1 and 150kgNha-1 were recommended for winter wheat and summer maize, respectively. Irrigation to the field capacity of 0-40cm and 0-60cm soil depth could be appropriate for maize and wheat, respectively. Therefore, taking grain yields, mineral N accumulation in the soil profile, nitrate leaching potential, and groundwater quality into account, coupled water and N management could provide an opportunity to promote grain production while reducing negative environmental impacts in this region.

Effects of soil properties and depth on fruit tree chlorosis in the loess region in Northern China

Abstract The loess region in northern China is an important area of apple (Pyrus malus L.) and pear (Pyrus communis L.) production due to its favorable soil and climate. In recent years, as the apple and pear production in this region rapidly increased, more orchards experienced iron deficiency chlorosis. However, information on soil nutrient status and fruit tree chlorosis of this region is scarce. In this research, we collected soil and fruit tree leaf samples from 25 pear and apple orchards (10 chlorotic orchards and 15 nonchlorotic orchards). Soil samples were collected at depths of 0–20 cm, 20–40 cm, 40–60 cm, and 60–80 cm. Soil organic matter, total nitrogen (TN), alkali‐hydrolyzable N, Olsen‐phosphorus (P), ammonium acetate‐potassium (K), DTPA‐iron (Fe), and less than 0.01‐mm soil particle content were analyzed, soil bulk density of 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm were also determined. Leaf samples were analyzed for chlorophyll content. Comparison of soil properties was performed between chlorotic orchard soils and nonchlorotic orchard soils; stepwise multiple regression was performed between leaf chlorophyll content and soil properties. The results indicated that those orchard soils were rich in P and K but deficient in Fe. Chlorotic orchard soils contained more K, bicarbonate and less than 0.01‐mm soil particles, and less DTPA‐Fe in certain layers than those of nonchlorotic orchard soils. Leaf chlorophyll content negatively correlated with soil bicarbonate, alkali‐hydrolysable N, and ammonium acetate‐K and positively correlated with TN, DTPA‐Fe, and bulk density at certain depths. Most of these soil properties that have a significant difference between these two kinds of orchard soils or affect leaf chlorophyll content occur below 40 cm in the soil profile. These results suggested that high bicarbonate content and low available Fe content in soils were the primary causes for fruit tree chlorosis in the loess region. Shallow groundwater table in the chlorotic orchards and root growth impairment in the surface soil because of tillage are supposed to be the reason why deeper depth in soil profile play an important role in fruit tree chlorosis in this region.

An ammonia sensor with high sensitivity in farmland based on laser absorption spectroscopy technology

High nitrogen fertilizer input is the main manner to maintain the high-yield crops in farmland in China. The average application quantity of nitrogen fertilizer in China is significantly higher than some developed countries in the world. However, the nitrogen fertilizer utilization efficiency is very low. Thus, high sensitivity sensing and on-line monitoring ammonia concentration were needed to quickly acquire the soil nutrient information and to get the nitrogen fertilizer utilization efficiency. A high sensitivity ammonia concentration sensor used in farmland has been developed based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology, high frequency modulation technique and long optical path technique. TDLAS is a method to obtain the spectroscopy of gas molecule single absorption line in the characteristic absorption spectrum region as the characteristic of the distributed feed back (DFB) laser with narrow line width and tunability. A sensor array formed with three ammonia concentration sensors by distributed sensing technique was used for ammonia volatilization experiment in a wide range of farmland. It was verified that the performance consistency of the three ammonia sensors was good and the sensor array realized the regional ammonia concentration monitoring. Continuous measurement results showed that the ammonia concentration influenced by the volatile source location, wind direction, weather and other factors, and it was positively correlated with the ammonia volatilization rate. The ammonia sensor array is suitable for continuously ammonia volatilization monitoring in a wide range of farmland environment with its high sensitivity, rapid response time without gas sampling.