Contrasting ability of deep and shallow rooting rice genotypes to grow through plough pans containing simulated biopores and cracks

Aims Cracks and biopores in compacted soil such as plough pans could aid deep rooting, mitigating constraints to seasonal upland use of paddy fields for rice production. This research investigated how soil macropores through a simulated plough pan affects root growth of contrasting deep and shallow rooting rice genotypes. Methods Deep rooting Black Gora and shallow rooting IR64 rice varieties were grown in packed cores of unsaturated soil in a controlled greenhouse. Simulated biopores and cracks (macropores) were inserted through the plough pan to form treatments with no macropores, biopores, cracks, and combined cracks and biopores. Different root parameters such as root length density (RLD), root volume, root diameter, number of root tips and branches were measured. The number of roots was calculated manually, including the number of roots growing through macropores in the plough pan layer. Results Plough pans with macropores had 25–32% more roots than with no macropores. RLD was 55% greater in the plough pan layer if cracks were present compared to biopores. Conversely, RLD was 26% less in subsoil if the plough pan had cracks compared to biopores. Different root parameters were greatly influenced by the presence of macropores in the plough pan, and deep-rooted Black Gora produced 81% greater RLD, 30% more root numbers and 103% more branching than the shallow rooted rice genotype IR64 within the plough pan layer. Conclusions Macropores greatly improve rice root growth through plough pans for a deep rooting but not a shallow rooting rice variety. Whereas cracks produce a greater number of roots in the plough pan, biopores result in greater root branching and root numbers deeper in subsoil.

Contrasting Ability of Deep and Shallow Rooting Rice Genotypes to Grow Through Plough Pans Containing Biopores and Cracks

Aims Cracks and biopores in compacted soil such as plough pans could aid deep rooting, mitigating constraints to seasonal upland use of paddy fields for rice production. This research investigated how soil macropores through a simulated plough pan affects root growth of contrasting deep and shallow rooting rice genotypes.Methods Deep rooting Black Gora and shallow rooting IR64 rice varieties were grown in packed cores of unsaturated soil in a controlled greenhouse. Artificial biopores and cracks (macropores) were inserted through the plough pan to form treatments with no macropores, biopores, cracks, and combined cracks and biopores. Different root parameters such as root length density (RLD), root volume, root diameter, number of root tips and branches were measured. The number of roots was calculated manually, including the number of roots growing through macropores in the plough pan layer.Results Plough pans with macropores had 25-32 % more roots than with no macropores. RLD was 55 % greater in the plough pan layer if cracks were present compared to biopores. Conversely, RLD was 26 % less in subsoil if the plough pan had cracks compared to biopores. Different root parameters were greatly influenced by the presence of macropores in the plough pan, and deep-rooted Black Gora produced 81% greater RLD, 30 % more root numbers and 103 % more branching than the shallow rooted rice genotype IR64 within the plough pan layer.Conclusions Macropores greatly improve rice root growth through plough pans for a deep rooting but not shallow rooting rice variety. Whereas cracks produce a greater number of roots in the plough pan, biopores result in greater root branching and root numbers deeper in subsoil.

Smash-ridging cultivation improves crop production

Smash-ridging cultivation is an efficient farming method that was recently developed in China. The technique involves vertically cutting by using a spiral drill, causing the soil to ‘suspend’ as ridges, thereby breaking through the traditional plough pan, and thickening the plough layer up to 30–50 cm. Smash-ridging cultivation has effectively improved soil quality and has increased the water and nutrient retention capacity. Loose soil enables the plant’s root system to optimally develop and more efficiently absorb nutrients. This facilitates the growth of the above ground parts of plant, leading to a significant increase in crop yield. This method has been successfully applied on 40 crops and tested in 26 provinces. The yield increase within a single season ranges from 10.0% to 54.8%. This technique may have a positive and extensive impact on food safety and agricultural production in China and the rest of the world.

INVESTIGATION AND ASSESSMENT OF SOIL DENSITY CHANGED BY REPEATED PASSES OF MIDDLE-WEIGHT TRACTORS WITH DIFFERENT DRIVE SYSTEMS

This work presents the investigation of the influence of repeated passes of medium-weight tractors with single wheels and additional wheels on the soil density to the depth of 0.4 m. The experiments were carried out in the Greater Poland Region (Poland), on light soil (Luvisol, loamy sand). The soil density was analysed in the arable layer at the two depths of 0.08–0.12 m and 0.18–0.22 m and in the plough pan at a depth of 0.30–0.34 m. The tractors weighing 52.1, 62.8 and 71.8 kN equipped with single wheels (standard wheels) and tractors weighing 52.1 and 71.8 kN equipped with additional wheels were used in the experiments. The research proved that repeated passes of the tractors with standard and addition wheels caused a linear or non-linear (logarithmic) increase in the soil density in the arable layer. Only light tractor 52.1 kN with dual wheels caused soil density increase in the hard pen. The above soil density changes inconsistent depend on the weight tractors and mean tractor pressure. Repeated passes of tractors with additional wheels resulted in lower soil density in the arable layer especially by second and third pass. A larger number of passes of middle-weight tractors with standard wheels as well with additional wheels increases the risk of reduced yield of cultivated plants.

Soil replacement combined with subsoiling improves cotton yields

Background Long-term rotary tillage has led to the deterioration of cotton production in northern China. This deterioration is due to the disturbance of topsoil, a dense plough pan at the 20–50 cm depth, and the decreased water storage capacity. A 2-yr field experiment was performed from 2014 to 2015 to explore a feasible soil tillage approach to halting the deterioration. The experiment consisted of four treatments: replacing the topsoil from the 0–15 cm layer with the subsoil from the 15–30 cm layer (T1); replacing the topsoil from the 0–20 cm layer with the subsoil from the 20–40 cm layer and subsoiling at the 40–55 cm layer (T2); replacing the topsoil from the 0–20 cm layer with the subsoil from the 20–40 cm layer and subsoiling at the 40–70 cm layer (T3); and conventional surface rotary tillage within 15 cm as the control (CK). Results The results indicated that the soil bulk densities at the 20–40 cm layer in T2 were 0.13 g·cm− 3 and 0.15 g·cm− 3 lower than those obtained from CK in 2014 and 2015, respectively. The total nitrogen (N) and the available phosphorus (P) and potassium (K) contents from the 20–40 cm layer in T2 and T3 were significantly higher than those in CK and T1. The amount of soil water stored in the 0–40 cm layer of T2 at the squaring stage of cotton was 15.3 mm and 13.4 mm greater than that in CK in 2014 and 2015, respectively, when the weather was dry. Compared with CK, T2 increased cotton lint yield by 6.1 and 10.2 percentage points in 2014 and 2015, respectively, which was due to the improved roots within the 20–60 cm layer, the greater number of bolls per plant and the higher boll weight in the T2 treatment. Conclusions The results suggested that soil replacement plus subsoiling would be a good alternative to current practices in order to break through the bottleneck constraining cotton production in northern China. Replacing the topsoil in the 0–20 cm layer with the soil from the 20–40 cm layer plus subsoiling at the 40–55 cm layer would be the most effective method.

Effect of subsoiling on tillers, root density and nitrogen use efficiency of winter wheat in loessal soil

A 2-year field experiment was carried out in loessal soil in a semi-humid climate to research winter wheat (Triticum aestivum L.) growth and nitrogen use efficiency. The result showed that subsoiling increased root penetration and promoted deep soil water absorption, which resulted in high resilience to the adverse dry climate. Soil NO₃^–-N residue throughout the profile was decreased but increased in rotary tillage. Grain yield was significantly increased by 21.9% and 11.3% in 2016 and 2017, respectively, mainly due to the significantly larger spikes per hectare and grains per spike. Nitrogen use efficiency was significantly improved by 26.7% in 2016 and 13.8% in 2017. For loessal soil in semi-humid climate, breaking the plough pan was necessary, and it was useful for the increase of grain yield and nitrogen use efficiency.