No abstract

No abstract

& Key message Combined drip irrigation and fertigation significantly increased stem volume and biomass production in a poplar plantation, and showed a cumulative effect over years. The promoting effects were mainly attributable to increased nitrogen and water availability in the surface soil through the combined management. & Context Fast-growing and high-yielding poplar plantations have been identified as major commercial forests in China. Intensive management of irrigation and fertilization can greatly increase productivity of plantations. Quantitative investigations on the cumulative effect of drip irrigation and fertigation over years are quite infrequent. & Aims We aimed to quantitatively evaluate the effects of drip irrigation and fertigation plans on tree growth and productivity in a poplar plantation, and to analyze their possible cumulative promoting effect over multiple years. & Methods Treatments including nine drip irrigation and fertigation combinations, and single furrow irrigation in spring as control, were conducted in a poplar plantation for three successive years. The combined treatments consist of three irrigation levels (WP −75 , WP −50 , and WP −25 , in ascending order) and three levels of nitrogen addition (N 60 , N 120 , and N 180 , in ascending order). Soil nitrogen and water content were measured throughout the 3 years. Based on tree surveys, tree growth, volume, and biomass production were evaluated each year. & Results Nitrogen and water availability in the surface soil increased in the drip irrigation-and fertigation-treated plots. Drip irrigation and fertigation treatments resulted in significant higher growth, stem volume, and biomass productions compared to control. Biomass increments in drip irrigation-and fertigation-treated plots were 4. 8-50.0, 5.3-26.5, and 4.3-52.2% higher than control in the three experimental years, respectively, with WP −25 N 180 and WP −50 N 180 recording the highest increments. Fertigation showed cumulative effects over multiple years and the positive effects increased with the dosage. However, irrigation showed little cumulative effect and the greatest effect was obtained under medium level. & Conclusion Combined drip irrigation and fertigation greatly promoted the plantation productivity. The combined management effect varied with application plans and plantation ages, and showed a cumulative effect over years.

& Key message Nitrogen addition through drip fertigation to a poplar plantation (Populus × euramericana BGuariento^) promoted fine root growth only in the early period. The relationship between root growth and soil N content was positive in the first 2 years, but became negative in the third year when the soil N availability had substantially increased. & Context Nitrogen (N) deficiency is common in forest soils, and N addition is sometimes applied in the case of intensive plantations. There is a need to better document the impact of N addition through the high-efficiency fertilization technique on fine root morphology and growth, given their importance for the uptake of nutrients and for tree growth. & Aims We aimed to quantitatively investigate the responses of fine roots in morphology and growth to N addition through surface drip fertigation over multiple years in a Populus × euramericana BGuariento^plantation. & Methods A field experiment that included four drip fertigation treatments with N addition levels (0, 60, 120, and 180 kg N ha −1 year −1 ) was conducted for three successive years. A coring method was used to sample soils and quantify the root morphological traits and soil N content along 0-60-cm profiles. & Results The root biomass density, length, surface area, specific length, and tissue density were significantly higher in the N addition treatments than those in the control after the first year, but the positive effect decreased in the second year. In the third year, root biomass in the N addition treatments was even lower by 11-39% than that in the control. The relationship between root growth and soil N content was also positive in the first 2 years and negative in the third year. & Conclusion N addition promoted fine root growth mainly in the shallow soil and in the early period of experiment. The relationship between root growth and soil N content became negative in the third year when the soil N availability had substantially increased. It is suggested that fine roots adjust their growth and morphology in response to N availability varying along the soil profile and with the fertilization duration.

No abstract