Ligeng Jiang

Changes in soil microbial properties with no-tillage in Chinese cropping systems

No-tillage (NT) has revolutionized agricultural systems because it has potential benefits including soil conservation and reduced production costs though saving in fuel, equipment, and labor. Soil quality is of great importance in determining the sustainability of land management systems, and soil microbial properties are becoming increasingly used to assess the effect of farming practices on soil quality due to their quick response, high sensitivity, ecological relevance, and capacity to provide information that integrates many environmental factors. In China, research and application of NT have developed quickly since 1970s. Numerous studies have been conducted in this country to evaluate the effect of NT on soil microbial properties. From these studies, it is evident that NT can lead to an increase in soil microbial size or activity or both and a consequent increase in soil microbial biomass in upland cropping systems. However, there are still several issues that remain unaddressed or inadequately specified. Further investigations are needed (1) to determine the effect of NT on soil microbial diversity by using molecular biological techniques in both upland and rice-based cropping systems; (2) to fully understand the changes of soil microbial properties with NT in rice-based cropping systems, especially for double rice cropping systems; and (3) to clarify the relationship between rhizosphere microbial properties and crop growth in NT rice cropping systems.

Root Morphology Was Improved in a Late-Stage Vigor Super Rice Cultivar

This study aimed to test the hypothesis that root morphology might be improved and consequently contributing to superior post-heading shoot growth and grain yield in late-stage vigor super rice. A pot experiment was carried out to compare yield attributes, shoot growth and physiological properties and root morphological traits between a late-stage vigor super rice cultivar (Y-liangyou 087) and an elite rice cultivar (Teyou 838). Grain yield and total shoot biomass were 7–9% higher in Y-liangyou 087 than in Teyou 838. Y-liangyou 087 had 60–64% higher post-heading shoot growth rate and biomass production than Teyou 838. Average relative chlorophyll concentration and net photosynthetic rate in flag leaves were 7–11% higher in Y-liangyou 087 than in Teyou 838 during heading to 25 days after heading. Y-liangyou 087 had 41% higher post-heading shoot N uptake but 17–25% lower root biomass and root-shoot ratio at heading and maturity than Teyou 838. Specific root length and length and surface area of fine roots were higher in Y-liangyou 087 than in Teyou 838 at heading and maturity by more than 15%. These results indicated that root-shoot relationships were well balanced during post-heading phase in the late-stage vigor super rice cultivar Y-liangyou 087 by improving root morphology including avoiding a too great root biomass and developing a large fine root system.

Nitrogen Uptake and Utilization by No-Tillage Rice under Different Soil Moisture Conditions – A Model Study under Simulated Soil Conditions

Abstract Most of the existing studies regarding water-saving cultivation on rice are based on tillage rice, rather than no-tillage rice. The purpose of this study was to quantify the effects of nitrogen fertilizer on no-tillage rice cultivation undervarious soil moisture conditions, in order to determine the suitable soil moisture content for rice production by no-tillage cultivation. Pot experiments were conducted in the early seasons of 2010 and 2011. In each season, a hybrid rice cultivar, Jiyou716, was planted under the soil moisture contents of 95 – 100% (W100), 80 – 85% (W85) and 65 – 70% (W70). 15N was used as the nitrogen fertilizer. Yield, dry matter accumulation, nitrogen concentration and 15N abundance of maturity were determined for each sample. The nitrogen loss of basal N-fertilizer (BF) and tillering N-fertilizer (TF) in W70 was 22 – 24% and 18 – 45% larger than in W100, respectively, resulting i reduction in nitrogen uptake and total nitrogen accumulation in plants. The yield of rice by no-tillage in W70 was 47 – 42% lower in 2011 and 2010. There was no significant difference between W85 and W100 in yield, nitrogen uptake and utilization in no-tillage cultivation. It was concluded that the N uptake and yield were decreased by decreasing soil moisture contents to 70% of saturation in no-tillage cultivation. Soil content of around 85% was proposed as a suitable condition without a large reduction in the yield and N use in water-saving cultivation, although a field test is essential for practical use.

Continuous applications of biochar to rice: Effects on nitrogen uptake and utilization

Improving soil quality is critical for increasing rice yield, and biochar could be a beneficial soil amendment for high yield. This study was conducted to determine the effects of continuous (repeated seasonal) applications of biochar on nitrogen (N) uptake and utilization in rice. A fixed field experiment was done in Yongan Town, Hunan Province, China, in six continuous seasons (the early and late rice-growing seasons from 2015 to 2017). Results showed that biochar application did not significantly affect soil N uptake in the first four seasons. The effect of biochar application on fertilizer N uptake was not significant in three of the first four seasons. In the fifth and sixth seasons, biochar application resulted in 14–26% increases in soil N uptake but 19–26% decreases in fertilizer N uptake. Soil N availability did not explain the increased soil N uptake with biochar application. The decreased fertilizer N uptake with biochar application was attributed to both decreased fertilizer N availability and increased N loss through ammonia volatilization. As a consequence of a compensation between the increased soil N uptake and the decreased fertilizer N uptake, the effect of biochar application on total N uptake was not significant in the fifth and sixth seasons. However, biochar application led to 7–11% increases in internal N use efficiency in the fifth and sixth seasons and 6% increase in grain yield in the sixth season. Our study suggests that the effects of repeated seasonal applications of biochar on N uptake and utilization in rice depend on the duration of biochar application. Longer continuous applications of biochar can increase internal N use efficiency and grain yield in rice with insignificant change in total N uptake.