Renzhi Zhang

Soil water content and photosynthetic capacity of spring wheat as affected by soil application of nitrogen-enriched biochar in a semiarid environment

A field trial was conducted to determine the effect of nitrogen-enriched biochar on soil water content, plant’s photosynthetic parameters, and grain yield of spring wheat at the Dingxi Experimental Station during the 2014 and 2015 cropping seasons. Results showed that biochar applied with nitrogen fertilizer at a rate of 50 kg ha–1 of N (BN50) increased soil water content in the 0–30 cm depth range by approximately 40, 32, and 53% on average at anthesis, milking, and maturity, respectively, compared with zero-amendment (CN0). Stomatal conductance and net photosynthetic rate after the BN50 treatment increased by approximately 40 to 50% compared to CN0. Soil water content and photosynthetic traits also increased in other treatments using straw plus nitrogen fertilizer, but to lesser extent than that of BN50. Grain yields were highest (1905 and 2133 kg ha–1 in 2014 and 2015, respectively) under BN50. From this, biochar appears to have a potential for its use with N-fertilizer as a cost-effective amendment for crop production in semiarid environments.

SOIL QUALITY INDICATORS AND CROP YIELD UNDER LONG-TERM TILLAGE SYSTEMS

Soil quality indicators (SQI) can be used as a synthetic tool for the assessment of the sustainability of agricultural systems. In this study, we developed SQI using minimum data set (MDS) and determined the response of SQI to long-term tillage systems. Field pea (Pisum sativum L.) and spring wheat (Triticum aestivum L.) were grown in alternate years at northwestern China, and soil attributes and crop productivity were measured 6 years after the initiation of the experiment. The MDS used to develop the SQI included soil physical (aggregate, bulk density, capillary porosity, field capacity), chemical (soil organic matter, total nitrogen, available phosphorus, available potassium) and biological (microbial count, microbial biomass, and the activities of catalase, urease, alkaline phosphatase, and invertase) properties. All the property variables were measured in each of the 0–5, 5–10 and 10–30 cm depths and those variables that contributed significantly to the SQI were selected to be included in the MDS. Amongst the measured variables, bulk density and microbial counts occurred in the MDS of all the three depths, suggesting that these two properties are highly affected by the tillage treatments. In the long-term field experiment, the no-till with stubble covering the soil surface treatment received the greatest SQI score and achieved the highest crop yield. Soil quality under tillage systems can be assessed adequately using MDS measured at the top soil (0–5 cm) layer in rainfed agro-ecosystems.

Evaluation of bacterial and fungal diversity in a long-term spring wheat – field pea rotation field under different tillage practices

Abstract: Soil management practices have the potential to modify the diversity and function of microbes in agricultural fields. The aim of this study was to investigate bacterial and fungal diversity in a 15 yr wheat–pea rotation tillage experiment. The treatments included conventional tillage with stubble removed, no-till with stubble removed, no-till with stubble retained (NTS), and conventional tillage with stubble incorporated. Illumina high-throughput sequencing platform was employed to sequence bacteria 16S rRNA (V3V4) and fungi internal transcribed spacer (ITS2) region genes in 0–10 cm and 10–30 cm of soil sampled. The dominant bacterial and fungal phyla identified at 97% similarity cutoff across both depths of treatments were Proteobacteria (26.3%), Actinobacteria (25.1%), Acidobacteria (15.0%), Gemmatimonadetes (8.8%), Ascomycota (85.8%), and Basidiomycota (8.0%). NTS had significantly (p < 0.05) higher microbial diversity indices, total organic carbon, soil microbial biomass carbon and nitrogen, NO3-N, and NH4-N at 0–10 cm depth. Tillage and stubble effects had a significant correlation with some phyla such as Proteobacteria, Actinobacteria, Gemmatimonadetes, JL-ETNP-Z39, Nitrospirae, Chloroflexi, Firmicutes, and other identified and unidentified minor microbial phyla. No-till and residue retention practices influenced fungal and bacterial species diversity through improved soil chemical properties, which have potential to affect the habitat and activity of soil microbes. Therefore, no-till and stubble retention could improve soil quality and promote sustainable agriculture in the rainfed Loess Plateau.

Effect of Conservational and Conventional Tillage Systems on Functional Soil Archaea Diversity in Wheat-Pea Rotation Field

Soil borne archaea in agricultural systems is crucial for cycling of nutrient such as Nitrogen, Carbon and Sulphur. The objective of the study was to assess the effect of different tillage systems on functional archaea diversity in a 15 years cereal-legume rotation field using Illumina sequencing platform for archaea 16S rRNA gene. The treatments in the study included conventional tillage with stubble removed (T), no-till with stubble removed (NT), conventional tillage with stubble incorporated (TS) and no-till with stubble retained (NTS). The results showed that the dominant soil archaea phyla was Crenarchaeota (> 96%), followed by Euryarchaeota with a lower abundance of NTS > TS > T for 16S rRNA number of OTUs, Shannon and Simpson indices calculated for the 0-10cm soil depth. Analysis of factor effect revealed that tillage but not stubble retention or their interaction significantly influenced (P < 0.01 and P < 0.05) 16S rRNA diversity. Non metric Multidimensional Scaling (NMDS) analysis clearly grouped the microbial communities according to depths. Linear Discriminant Analysis Effect Size (LEfSe) identified Crenarchaeota and Thaumarchaeota (to genus level) as significantly enriched clades in 0-10 cm depth of T while Euryarchaeota and Thermoplasmata were significantly enriched in TS. The conservational tillage systems (NT and NTS) promoted even distribution of archaea diversity while conventional tillage systems (T and TS) enriched the archaea communities identified in the study.