Maize leaf-removal: A new agronomic approach to increase dry matter, flower number and seed-yield of soybean in maize soybean relay intercropping system

Abstract

Shading conditions adversely affect flower-number and pod-number of soybeans under maize-soybean relay-intercropping (MSR). Here we reveal that leaf-removal from maize-canopy improves the photosynthetically active radiation (PAR) transmittance and dry-matter production (DMP) of soybean (especially during the co-growth phase), and compensates the maize seed-yield loss by considerably increasing soybean seed-yield. In a two-year experiment with MSR, maize-plants were subjected to different leaf-removal treatments to increase the PAR-transmittance of soybean; removal of the topmost two-leaves (R2), four-leaves (R4), six-leaves (R6), with no-removal of leaves (R0). Leaf-removal treatments improved the PAR-transmittance, photosynthetic-rate, and morphological-characteristics of soybean under MSR. At 90 days after sowing, the dry-matter of pods, and seeds was increased by 25%, and 32%, respectively under R6 than R0. Importantly, enhanced PAR-transmittance and DMP under R6 enabled soybean to initiate a greater number of flowers 182.2 plant−1 compared to 142.7 plant−1 under R0, and it also decreased the flower-abscission (by 13%, from 54.9% under R0 to 47.6% under R6). These positive responses increased the pod-number by 49% and seed-number by 28% under R6 than R0. Overall, under R6, relay-intercropped soybean produced 78% of sole-soybean seed-yield, and relay-intercropped maize produced 81% of sole-maize seed-yield and achieved the land equivalent ratio of 1.59.

Growth Rate, Dry Matter Accumulation, and Partitioning in Soybean (Glycine max L.) in Response to Defoliation under High-Rainfall Conditions

“…Thus, it is possible that with increased photosynthesis and light use efficiency, soybean plants with a little lower leaf area at R 3 , R 4 , and R 5 could save dry matter investment on the development and maintenance of extra vegetative parts. These dry matter savings could then be shifted to increase the final seed yield of soybean by increasing the pod initiation [ 5 ] and decreasing seed abortion [ 11 ].…”

“…In this study, a slight reduction in the leaf area of soybean plants at R 3 significantly increased the number of pods and seeds through increased pod initiation and decreased seed abortion, respectively, by maintaining enough supply of carbohydrates to reproductive parts. Thus, under high-rainfall conditions, soybean requires a higher supply of photoassimilates to reduce pod abscission and seed abortion because, with an adequate supply of assimilates, each initiated pod and seed can develop into a mature pod and seed at final harvest [ 11 ]. However, mutual shading of leaves significantly reduces the net photosynthetic rate and carbohydrate supply to developing pods in soybean, especially at the pod initiation and seed initiation stages [ 43 ].…”

“…Therefore, we can conclude that the improved seed yield of soybean in T 1 might be associated with the improved PAR transmittance and dry matter accumulation, leading to a higher partitioning of dry matter and nutrients to developing pods and seeds from R 3 to R 7 . Delayed leaf senescence maintained the continuous assimilate supply, which reduced the pod abscission and seed abortion rate in soybean plants [ 11 , 43 ]. Therefore, the slight defoliation significantly increased the final pod and seed number, which increased the final seed yield.…”

“…Therefore, modern and sustainable agronomic approaches are required now to fulfill the future demands for food crops [ 9 ], which we will face in the midcentury [ 10 ]. Thus, meeting the predicted world demand for food crops will require new crop production practices or methods beyond that employed in the green revolution [ 11 , 12 ].…”

Defoliation impacts on morpho-physiological attributes and yield of tomato

“…These results suggest that under normal condition, assimilate accumulation is operating below its maximum potential. When source-sink ratios of whole plants were lowered experimentally, net photosynthetic and net assimilation rates of the remaining leaves increased 10-20% in soybean (Raza et al, 2019) and 18% in maize (Liu et al, 2014). Other authors have found that partial defoliation of plants stimulated the photosynthetic rates of the remaining leaves (Silva et al, 2011;Verhuel, 2012).…”