A two-year experiment was carried out at Shenyang Agricultural University’s research field area in China to evaluate the impact of the combined application of straw mulch (0 and 8 t ha⁻¹) and biochar (0, 4, 12, and 36 t ha⁻¹) on the morphological traits and grain development of rainfed maize during 2018 and 2019. The results showed that straw mulch and different biochar application rates significantly impacted the maize growth index. Compared to non-biochar-treated soils, the introduction of straw mulch improved plant height, stem diameter, leaf area index (LAI), leaves, stem, root, and crop growth rate (CGR), and dry weight of rainfed maize crop. The highest plant height, stem diameter, LAI, leaves, stem, root growth rate, CGR, and dry weight of rainfed maize crop were reported when soil was treated with a higher rate of biochar (36 t ha⁻¹). Biochar increased grain filling rate while decreasing grain filling duration in rainfed maize crops. Our results indicate that straw mulch and biochar-based soil management strategies can improve the rainfed maize growth with the environmental benefits of global warming mitigation. However, due to the wide range of biochar properties, the interactions between straw mulch and biochar should be given special consideration in the maize cropping system.

Phosphorus (P) application in the soil improves soil fertility and thus contributes to reproductive organ development, resulting in a higher cotton yield. However, the effect of increasing phosphorus rate on soil nutrient status, phosphorus-related enzyme activities, and its effects on crop productivity needs excellent attention. A consecutive two-year (2017-2018) field experiment containing three phosphorus levels [0 (P1), 100 (P2), and 200 (P3) kg P2O5 ha-1] was accomplished by maintaining three replications. During both cropping years, soil samples were gathered from the topsoil (0-20 cm) and subsurface (20-40 cm) during the harvesting stage of the cotton crop. Soil collected at topsoil showed a significant increase in available and total phosphorus contents and urease and acid, alkaline, and neutral phosphatase enzyme activities compared with the sub-soil. The soil nutrients, viz. ammonium, nitrate, total nitrogen, available potassium, and total potassium, were significantly higher in P3 at the topsoil compared to other treatments. Soil enzymes viz. urease and acid, alkaline, and neutral phosphatase activities in the P3 were improved compared to the P1 and P2 applications. On average, the activities of these enzymes were maximum in 2017 at both soil depths. Moreover, the maximum biomass accumulation was observed in vegetative (root, stem, and leaves) and reproductive (bur, lint, and seed) organs with P3 incorporation in the soil. Similarly, an increase in the phosphorus application rate significantly enhanced the plant biomass and seed cotton yield during the 2017 and 2018 cropping seasons. Conclusively, the findings of this study showed that the P3 (200 kg P2O5 ha−1) rate enhanced cotton productivity by improving the soil physicochemical properties, which alternately enhanced the phosphorus availability to the crop. Thus, changing these properties of the soil resulted in the enhancement of soil enzyme activities by increasing the cotton yield under field conditions.

Introduction: Biochar (BC) and nitrogen (N) application have the potential to increase grain yield and resource use efficiency in intercropping systems. However, the effects of different levels of BC and N application in these systems remain unclear. To address this gap, the study is intended to ascertain the impact of various combinations of BC and N fertilizer on the performance of maize-soybean intercropping and determine the optimum application of BC and N for maximizing the effect of the intercropping system.Methods: A two-year (2021-2022) field experiment was conducted in Northeast China to assess the impact of BC (0, 15, and 30 t ha^-1) and N application (135, 180, and 225 kg ha^-1) on plant growth, yield, water use efficiency (WUE), N recovery efficiency (NRE) and quality in an intercropping system. Maize and soybean were selected as materials in the experiment, where every 2 rows of maize were intercropped with 2 rows of soybean.Results and discussion: The results showed that the combination of BC and N significantly affected the yield, WUE, NRE and quality of intercropped maize and soybean. The treatment of 15 t ha^-1 BC and 180 kg ha^-1 N increased grain yield and WUE, while that of 15 t ha^-1 BC and 135 kg ha^-1 N enhanced NRE in both years. Nitrogen promoted the protein and oil content of intercropped maize, but decreased the protein and oil content of intercropped soybean. BC did not enhance the protein and oil content of intercropped maize, especially in the first year, but increased maize starch content. BC was found to have no positive impact on soybean protein, but it unexpectedly increased soybean oil content. The TOPSIS method revealed that the comprehensive assessment value first increased and then declined with increasing BC and N application. BC improved the performance of maize-soybean intercropping system in terms of yield, WUE, NRE, and quality while N fertilizer input was reduced. The highest grain yield in two years was achieved for BC of 17.1-23.0 t ha^-1 and N of 156-213 kg ha^-1 in 2021, and 12.0-18.8 t ha^-1 BC and 161-202 kg ha^-1 N in 2022. These findings provide a comprehensive understanding of the growth of maize-soybean intercropping system and its potential to enhance the production in northeast China.

Introduction: Intercropping and straw mulching are sustainable agricultural practices that can positively affect crop growth and development, especially together.Methods: A split-plot experimental design was used to investigate the effects of intercropping and straw mulching on crop growth, crop yield, nitrogen uptake, and photosynthetic characteristics. The main plot focused on three planting patterns: soybean monoculture (S), maize monoculture (M), and maize/soybean intercropping (I). The subplot structure consisted of four levels of straw mulching (0, 4.8, 7.2, 9.6 t ha^-1).Results: Interaction and variance analyses showed that straw mulching, intercropping, and their interaction had significant effects on plant height, stem diameter, leaf area index, chlorophyll content, nitrogen uptake, photosynthetic characteristics, and crop yield. Based on two-year averages for maize and soybean, the net photosynthetic rate (Pn) was up to 51.6% higher, stomatal conductance (Sc) was up to 44.0% higher, transpiration rate (Tr) was up to 46.6% higher, and intercellular carbon dioxide concentration (Ci) was up to 25.7% lower relative to no mulching. The maximum increases of Pn, Sc, and Tr of intercropped maize were 15.48%, 17.28%, and 23.94%, respectively, and the maximum Ci was 17.75% lower than that of monoculture maize. The maximum increase of Pn, Sc, and Tr of monoculture soybean was 24.58%, 16.90%, and 17.91%, respectively, and the maximum Ci was 13.85% lower than that of intercropped soybean. The nitrogen uptake of maize and soybean in the mulching treatment was 24.3% higher than that in the non-mulching treatment; the nitrogen uptake of intercropped maize was 34.2% higher than that of monoculture maize, and the nitrogen uptake of monoculture soybean was 15.0% higher than that of intercropped soybean. The yield of maize and soybean in the mulching treatment was 66.6% higher than that in the non-mulching treatment, the maize yield under intercropping was 15.4% higher than that under monoculture, and the yield of monoculture soybean was 9.03% higher than that of intercropped soybean.Discussion: The growth index and photosynthesis of crops are important parts of yield formation. The results of this study confirmed that straw mulching, intercropping, and their interaction can ultimately increase crop yield by improving crop growth, nitrogen uptake, and photosynthesis. This result can be used as the theoretical basis for the combined application of these measures in agriculture.