Wheat and maize-derived water-washed and unwashed biochar improved the nutrients phytoavailability and the grain and straw yield of rice and wheat: A field trial for sustainable management of paddy soils.

A field experiment was carried out to evaluate the effects of different biochars on grain yield and phytoavailability and uptake of macro- and micro-nutrients by rice and wheat grown in a paddy soil in a rotation. Soil was treated with i) maize raw (un-washed) biochar (MRB), ii) maize water-washed biochar (MWB), iii) wheat raw biochar (WRB) or iv) wheat water-washed biochar (WWB) and untreated soil was used as control (CF). Inorganic fertilizers were applied to all soils while biochar treated soils received 20 ton ha-1 of designated biochar before rice cultivation in rice-wheat rotation. The WRB significantly (P < 0.05) increased rice grain yield and straw by up to 49%, compared to the CF. Biochar addition, particularly WRB, significantly increased the availability of N, P, K and their content in the grain (26-37%) and straw (22-37%) of rice and wheat. Also, the availability and grain content of Fe, Mn, Zn, and Cu increased significantly after biochar addition, particularly after the WRB, due to WRB water dissolved C acting as a carrier for micronutrients in soil and plant. However, the water-washing process altered biochar properties, particularly the water extractable C, which decreased its efficiency. Both wheat- and maize-derived biochars, particularly the WRB, are recommended to improve nutrients availability and to improve grain yield in the rice-wheat rotation agro-ecosystem. These results shed light on the importance of crop straw transformation into an important source for soil C and nutrients necessary for sustainable management of wheat-rice agro-ecosystem. However, with the current and future alternative energy demands, the decision on using crop biomass for soil conservation or for bioenergy becomes a challenge reliant on regulatory and policy frameworks.

Evaluation of orange peel waste and its biochar on greenhouse gas emissions and soil biochemical properties within a loess soil.

The environmentally safe disposal of the large quantity of orange peels waste produced each day causes economic and environmental problems, which after conversion into biochar via pyrolysis technique might be used as an effective soil amendment. In this study, a 90-day incubation experiment was conducted to investigate the effects of orange peel waste and waste-derived biochar amendments on greenhouse gas emissions (GHG), soil biochemical properties, and soil enzyme activities. There were five treatments with different amendment levels: control without an amendment (Control), orange waste 1% (W1), orange waste 2% (W2), orange waste biochar 1% (B1), and orange waste biochar 2% (B2). The results showed that, compared with control, the amendments decreased cumulative N2O emissions by 59.2% (B2), 45.2% (B1), 20.6% (W2) and 10.2% (W1), respectively; and increased cumulative CH4 emissions by 81.7% (W1), 84.4% (W2), 75.8% (B1) and 74.9% (B2), respectively. Cumulative CO2 emissions decreased for the B1 (29.3%) and B2 (43.5%) over the waste treatments. While soil pH, SOC, nitrate nitrogen (NO3--N) and enzyme activities (urease and catalase) were significantly increased with the passage of time from the biochar amendments, ammonium nitrogen (NH4+-N) and invertase activities did not show this trend with time. Our study suggests that orange peel waste conversion to biochar should be a viable alternate method of disposal since land application resulted in reduced GHG and improvements in soil fertility.

Effects of Different Biochars on Wheat Growth Parameters, Yield and Soil Fertility Status in a Silty Clay Loam Soil.

The conversion of organic wastes into biochar via the pyrolysis technique could be used to produce soil amendments useful as a source of plant nutrients. In this study, we investigated the effects of fruit peels and milk tea waste-derived biochars on wheat growth, yield, root traits, soil enzyme activities and nutrient status. Eight amendment treatments were tested: no amendment (CK), chemical fertilizer (CF), banana peel biochar 1% (BB1 + CF), banana peel biochar 2% (BB2 + CF), orange peel biochar 1% (OB1 + CF), orange peel biochar 2% (OB2 + CF), milk tea waste biochar 1% (TB1 + CF) and milk tea waste biochar 2% (TB2 + CF). The results indicated that chlorophyll values, plant height, grain yield, dry weight of shoot and root were significantly (p < 0.05) increased for the TB2 + CF treatment as compared to other treatments. Similarly, higher contents of nutrients in grains, shoots and roots were observed for TB2 + CF: N (61.3, 23.3 and 7.6 g kg-1), P (9.2, 10.4 and 8.3 g kg-1) and K (9.1, 34.8 and 4.4 g kg-1). Compared to CK, the total root length (41.1%), surface area (56.5%), root volume (54.2%) and diameter (78.4%) were the greatest for TB2 + CF, followed by BB2 + CF, OB2 + CF, TB1 + CF, BB1 + CF, OB1 + CF and CF, respectively. However, BB + CF and OB + CF treatments increased ß-glucosidase and dehydrogenase, but not urease activity, as compared to the TB + CF amendment, while all enzyme activity decreased with the increased biochar levels. We concluded that the conversion of fruit peels and milk tea waste into biochar products contribute the benefits of environmental and economic issues, and should be tested as soil amendments combined with chemical fertilizers for the improvement of wheat growth and grain yield as well as soil fertility status under field conditions.

Co-Application of Milk Tea Waste and NPK Fertilizers to Improve Sandy Soil Biochemical Properties and Wheat Growth.

Desert soil is one of the most severe conditions which negatively affect the environment and crop growth production in arid land. The application of organic amendments with inorganic fertilizers is an economically viable and environmentally comprehensive method to develop sustainable agriculture. The aim of this study was to assess whether milk tea waste (TW) amendment combined with chemical fertilizer (F) application can be used to improve the biochemical properties of sandy soil and wheat growth. The treatments included control without amendment (T1), chemical fertilizers (T2), TW 2.5% + F (T3), TW 5% + F (T4) and TW 10% + F (T5). The results showed that the highest chlorophyll (a and b) and carotenoids, shoot and root dry biomass, and leaf area index (LAI) were significantly (p < 0.05) improved with all amendment treatments. However, the highest root total length, root surface area, root volume and diameter were recorded for T4 among all treatments. The greater uptake of N, P, and K contents for T4 increased for the shoot by 68.9, 58.3, and 57.1%, and for the root by 65.7, 34.3, and 47.4% compared to the control, respectively. Compared with the control, T5 treatment decreased the soil pH significantly (p < 0.05) and increased soil enzyme activities such as urease (95.2%), ß-glucosidase (81.6%) and dehydrogenase (97.2%), followed by T4, T3, and T2. Our findings suggested that the integrated use of milk tea waste and chemical fertilizers is a suitable amendment method for improving the growth and soil fertility status of sandy soils.

Beneficial effects of tobacco biochar combined with mineral additives on (im)mobilization and (bio)availability of Pb, Cd, Cu and Zn from Pb/Zn smelter contaminated soils.

The efficacy of tobacco biochar (TB) alone and in combined with mineral additives: Ca-hydroxide (CH), Ca-bentonite (CB) and natural zeolite (NZ), on immobilization of Pb, Cd, Cu and Zn, via reduce its (bio) availability to plants were investigated. The soils were collected from Tongguan contaminated (TG-C), Fengxian heavily contaminated (FX-HC) and Fengxian lightly contaminated (FX-LC) fields, Shaanxi province, China. The contaminated top soils were treated with low-cost amendments with an application rate of 1% and cultivated by Chinese cabbage (Brassica campestris L.) under greenhouse condition. Results showed that the all amendments (p < 0.05) potentially maximum reduced the DTPA-extractable Pb 82.53, Cd 31.52 and Cu 75.0% with TB + NZ in FX-LC soil, while in case of Zn 62.21% with TB + CH in FX-HC soil than control. The addition of amendments clearly increased dry biomass of Brassica campestris L. as compared with un-amended treatment (except TB + CH). Furthermore, these amendments markedly increased the uptake by plant shoot viz, Cd 10.51% with TB alone and 11.51% with TB + CB in FX-HC soil, similarly in FX-LC Cd increased 5.15% with TB + CH and 22.19% with TB + NZ, respectively. In same trend the Cu uptake in plant shoot was 19.30% with TB + CH in TG-C, whereas 43.90 TB + CH and 19.24% with TB + NZ in FX-LC soil. On the other hand as compared to control Cu accumulation in plant root was observed by TB, TB + CH and TB + CB treatments, while maximum uptake was 62.41% with TB + CH in TG-C soil. Consequently, except TB + CH treatment the chlorophyll content potentially increased in all amendment than control treatment, because of changes in soil EC, pH but increased CEC values after application of amendments. The results of this pot experiment are promising but they will further need to be confirmed with long-term field experiments.

Potential use of lime combined with additives on (im)mobilization and phytoavailability of heavy metals from Pb/Zn smelter contaminated soils.

This explorative study was aimed to assess the efficiency of lime alone and in combined with additives to immobilize Pb, Cd, Cu and Zn in soil and reduce their phytoavailability for plant. A greenhouse pot experiment was performed by using low and heavily contaminated top soils viz. Tongguan contaminated (TG-C); Fengxian heavily contaminated (FX-HC) and Fengxian low contaminated (FX-LC). The contaminated soils were treated with lime (L) alone and in combined with Ca-bentonite (CB), Tobacco biochar (TB) and Zeolite (Z) at 1% and cultivated by Chinese cabbage (Brassica campestris L). Results revealed that all amendments (p< 0.05) significantly reduced the DTPA-extractable Pb 97.33, Cd 68.06 and Cu 91.11% with L+TB, L+CB, L+Z in FX-LC soil and Zn 87.12% respectively, with L+CB into TG-C soil. Consequently, the application of lime alone and in combined with additives were drastically decreased the dry biomass yield of Brassica campestris L. as compared with control. Thus, these feasible amendments potentially maximum reduced the uptake by plant shoots upto Pb 53.47 and Zn 67.93% with L+Z and L+TB in FX-LC soil, while Cd 68.58 and Cu 60.29% with L+TB, L+CB in TG-C soil but Cu uptake in plant shoot was observed 27.26% and 30.17% amended with L+TB and L+Z in FX-HC and FX-LC soils. On the other hand, these amendments were effectively reduced the potentially toxic metals (PTMs) in roots upto Pb77.77% L alone in FX-HC, Cd 96.76% with L+TB in TG-C, while, Cu 66.70 and Zn 60.18% with L+Z in FX-LC. Meanwhile, all amendments were responsible for increasing soil pH and CEC but decreased soils EC level. Based on this result, these feasible soil amendments were recommended for long term-study under field condition to see the response of another hyper accumulator crop.