Impact of maize cob and wood-derived biochar on soybean plant growth and soil aggregate structure in dry land
Authors: Ma Hua , Li Qirui , Bellingrath-Kimura Sonoko D. 
Published: March 2020

&lt;p&gt;Soil structure plays important roles in land degradation, soil fertility, and agricultural productivity and thus has great ecological importance. Soil aggregation is a crucial soil function for maintaining soil porosity and enhancing the stability of soil structure to prevent soil erosion. Biochar was reported to be a binding agent for organic matter in aggregate formation and thus alleviate aggregates degradation. Therefore, this study attempts&amp;#160;to a) investigate the impact of the biochar on soybean plant growth, plant nutrients content and soil chemical properties; b) analyze the effect of maize cob biochar (CB) and wood biochar (WB) on soil aggregate structure in vulnerable dry land area.&lt;/p&gt;&lt;p&gt;Field trial was performed on two sandy soil fields (at MLZ and BDG village)&amp;#160;and one loamy clay soil field (at RQ village) which located in Ningxia, China. Two treatments (20 t ha&lt;sup&gt;-1&lt;/sup&gt;&amp;#160;of CB&amp;#160;and WB application) and control were repeated 7 times. In this study, we analyzed biomass, grain yield, and nutrients content of soybean plant while soil nutrients&amp;#160;were&amp;#160;observed as well. Nine soil aggregate size classes (ASCs) were obtained&amp;#160;(&gt;10, 10-7, 7-5, 5-3, 3-2, 2-1, 1-0.5, 0.5-0.25 and &lt;0.25 mm)&amp;#160;through&amp;#160;dry sieving to analyze soil structure.&amp;#160;In addition, soil dry mean weight diameter (dMWD), dry geometric mean diameter (dGMD), and structure coefficient (Ks) were measured&amp;#160;to estimate the aggregate stability, erodible fraction, and agronomically valuable fraction. After that, redundancy analysis and ridge regression analysis were applied for further data processing.&lt;/p&gt;&lt;p&gt;Our results&amp;#160;indicated&amp;#160;&lt;strong&gt;a&lt;/strong&gt;&lt;strong&gt;)&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;bio&lt;/strong&gt;&lt;strong&gt;m&lt;/strong&gt;&lt;strong&gt;ass&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;and&lt;/strong&gt;&lt;strong&gt;&amp;#160;gr&lt;/strong&gt;&lt;strong&gt;ain&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;yie&lt;/strong&gt;&lt;strong&gt;ld&lt;/strong&gt;&lt;strong&gt;:&lt;/strong&gt;&amp;#160;both CB and WB significantly increased shoot biomass in loamy clay soil by 48.7% and 45.0%, respectively. In the two sandy soils, biochar indicated no significant enhancement on the plant growth and grain yield. Even though, the mean value of grain yield&amp;#160;increased by 29.7% and 35.1% with the CB and WB application in the MLZ field, respectively. CB application also increased the mean value of&amp;#160;grain yield by 34.2% in the BDG field. Although the data&amp;#160;shows insignificant difference with high standard errors due to field heterogeneity,&amp;#160;the mean values&amp;#160;can&amp;#160;still give insights&amp;#160;into&amp;#160;agricultural field practices;&amp;#160;&lt;strong&gt;b&lt;/strong&gt;&lt;strong&gt;)&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;soil&lt;/strong&gt;&lt;strong&gt;&amp;#160;ag&lt;/strong&gt;&lt;strong&gt;gre&lt;/strong&gt;&lt;strong&gt;gat&lt;/strong&gt;&lt;strong&gt;e&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;stru&lt;/strong&gt;&lt;strong&gt;c&lt;/strong&gt;&lt;strong&gt;ture&lt;/strong&gt;&lt;strong&gt;:&lt;/strong&gt;&amp;#160;soil type exerted stronger influence on soil aggregation and plant growth rather than biochar.&amp;#160;The sandy field in MLZ showed high soil loss potential by wind erosion referring&amp;#160;to a&amp;#160;low value of dGMD, and the loamy clay field showed the highest dMWD, dGMD and Ks values&amp;#160;for&amp;#160;an ideal aggregate structure for crop growth. Findings indicate that biochar had no significant influence on aggregate structure in both sandy and loamy clay soils;&amp;#160;&lt;strong&gt;c&lt;/strong&gt;&lt;strong&gt;) &lt;/strong&gt;&lt;strong&gt;soil&lt;/strong&gt;&lt;strong&gt;&amp;#160;nut&lt;/strong&gt;&lt;strong&gt;rients&lt;/strong&gt;&lt;strong&gt;:&lt;/strong&gt;&amp;#160;CB can significantly increase&amp;#160;soil total carbon content in RQ and BDG fields. Soil potassium content can be&amp;#160;enhanced by CB application in loamy clay soil.&lt;/p&gt;