Continuous Wheat in Semiarid Regions

Abstract

Continuous wheat (Triticum aestivum L.) cropping in semiarid regions results in variable dry matter production. As a consequence, the balance of soil organic carbon (SOC) may vary across time. The aim of this research was to assess the dynamics and long-term changes of physically and chemically extracted SOC fractions. Soil samples (0-to 5-, 5-to 10-, and 10-to 20-cm depths) from continuous wheat with (f) and without (nf) fertilizer (N + P) under conventional tillage ((CT) for 25 years) and no-tillage ((NT) for 6 years) were taken during the experiment. Mineralassociated ((MOC) 0-0.053 mm), fine particulate ((POC f ) 0.053-0.100 mm), and coarse particulate ((POC c ) 0.1-2.0 mm) SOC and humic substances were obtained. The SOC variability depended on water availability during fallow periods (SOC decomposition) or crop cycles (dry matter production). The mean wheat yields were 1.33 (nf) and 2.09 (f) Mg grain ha −1 , with an estimated carbon input of 1.64 (nf) and 2.20 (f) Mg C ha −1 year −1 . Losses from the initial level were higher in labile fractions, POC c (−75%) and POC f (−53%), than in MOC (−15%). Humic acids present slight differences in their structure and quantity as a result of long-term cropping. Conversion from CT to NT resulted in contrasting results. For an equivalent soil mass, fertilizer application increased SOC by 4.31 Mg ha −1 (under CT) and 7.29 Mg ha −1 (under NT). The SOC turned out to be higher under NT with fertilizer use and lower without application. No-tillage does not increase SOC content by itself; it must be combined with other agricultural practices such as fertilization and/or crop rotation.Values within each column followed by different letters are significantly different according to the LSD test (P < 0.05).Galantini et al.

Washing agents from sewage sludge: efficiency of Cd removal from highly contaminated soils and effect on soil organic balance

“…However, although some researchers have reported changes in soil properties after washing, they have analyzed mostly basic soil properties and soil fertility. Moreover, the reported organic balances were based only on total OM content, and changes in HS and their fractions were not documented, even though it is known that the quality of HS or of their fractions can be changed by soil management practices (Reddy et al 2014;Galantini et al 2014).…”

Quality and Quantity of Organic Fractions as Affected by Soil Depth in an Argiudoll under Till and No-till Systems

“…Taking into account that transformation of soil organic materials follows the POCc -POCf -MOC sequence [17,35], the relationship among these organic fractions can be used as an indicator of SOC dynamics (Table 1). In NT, the POCc:POCf:MOC ratio showed a slow increase of humified compounds with depth.…”

“…It is well-known that particulate organic matter (POM) is more sensitive in detecting short-term changes than mineral associated organic matter (MOM). However, POM content can be modified by weather conditions or crop cycles [15] and hence the separation of SOM in different sand sizes can help to distinguish time-weather variability from management variability [16,17].…”

Short-Term Effects of Changing Soil Management Practices on Soil Quality Indicators and Crop Yields in Greenhouses

“…Although total organic carbon is the most widely used indicator to assess soil quality, soil productivity and agricultural sustainability [24,25], it is generally accepted that the change in its content is not very sensitive in the short and medium term [26,27], so labile fractions-which often include particulate organic carbon (POC), light fraction (LF), and water-soluble organic carbon (WSOC) [28]-have been used as short-term indicators after changing soil management practices [29][30][31][32][33][34]. POC, LF and WSOC are three fractions considered active in the nutrient cycles, readily available for microbial breakdown and closely associated with nutrient supply to crops [35,36].…”