ABSTRACT For the synergistic improvement of soil fertility and rice yields in a cold region, we investigated the effects of plastic mulching with different straw incorporation rates on the rice yield and nitrogen use efficiency in a rice growing area of a cold region. The field experiment was conducted using the Jijing 88 rice cultivar, and set up four straw incorporated treatment: 20% (S1), 40% (S2), 60% (S3) and 100% (S4) under two conditions: mulching (M) and without mulching (NM). The results showed that under the same straw incorporation rates: (1) Plastic mulching increased the total soil nitrogen and organic matter contents while improving the grain yield; the yield increases were 2.8–14.9% in 2016 and 1.4–12.3% in 2017. (2) The mulched treatment improved the net photosynthetic rate, the maximum tiller number, the crop growth rate of the later growth stages, and the shoot dry weight. (3) The recovery efficiency, agronomic efficiency, and partial factor productivity of the nitrogen applications were all higher under the mulched treatment than under the non-mulched treatment. In a comparison of the different straw incorporation treatments, above three indicators consistently increased before they decreased, and significantly higher levels were reached under the 40% straw incorporation treatment with mulching than under the other treatments.

ABSTRACT Sugarcane (Saccharum L. spp. hybrids) is a globally important crop. While roots contribute to its net primary production, knowledge of sugarcane root growth is incomplete and limited in scope. The objective of this study was to determine cumulative root density (LA), root distribution, effective rooting depth (ERD), and root growth rate for four sugarcane genotypes across three crop cycles (plant cane [PC], first ratoon [FR], and second ratoon [SR]). The experiment was conducted in a rain shelter on four sugarcane genotypes (ROC22, YZ04-241, YZ05-194, and YZ05-51) using minirhizotron tubes to a soil profile depth of 1.08 m. Most roots in were found at 0–0.36 m-depth, and about 85.0% were within a 0–0.72 m depth in PC. In FR and SR, however, > 81.8% of roots were found at 0–0.54 m-depth regardless of genotype. The LA of ROC22 was often significantly higher than that of the other genotypes at depths < 0.54 m regardless of crop cycle. The genotype ROC22 had greater root length and faster root growth rate than YZ05-194 at 0.18–0.36 m in PC and FR, while SR YZ05-194 had slower root growth than the other genotypes at 0–0.18m. Ratooning ability of sugarcane genotypes may be related to these root growth attributes.

A elevação da quantidade de mudas de alta qualidade associada ao descarte das de baixa qualidade pode aprimorar os programas de seleção e melhoramento genético da cana-de-açúcar (Saccharum spp.). Este trabalho avaliou a capacidade do método Dynamic Technique for Order Preference by Similarity to Ideal Solution (DTOPSIS) de identificar famílias da cana-de-açúcar com elevada qualidade. As características avaliadas foram: Brix, aptidão para moagem, diâmetro do caule, altura e porcentagem de tecido parenquimatoso. Os dados foram coletados em dois experimentos com 17 famílias e duas cultivares incluindo cana soca e brota. O DTOPSIS estima o índice Ci que expressa a proximidade de uma solução particular à ideal. O Ci foi utilizado para avaliar a distância de cada família à família ideal. As demais mudas foram utilizadas em um programa tradicional de seleção. Os valores de Ci de cada família foram comparados às taxas de seleção de famílias obtidas pelo programa tradicional de seleção por meio da estimação das taxas de seleção nos estágios 1 a 4. Os resultados indicaram que os valores de Ci calculados a partir dos experimentos foram significativamente correlacionados (p<0,01) às taxas de seleção do estágio 2 (r=0,8059), estágio 3 (r=0,7967) e estágio 4 (r=0,8202). Os resultados também indicaram que clones com promissor uso apresentam elevados valores de Ci. Conclui-se, portanto, que o método DTOPSIS é apropriado para selecionar e descartar mudas de alta e baixa qualidade, respectivamente, podendo elevar a eficiência dos programas de seleção.

Enlarging the quantity of seedlings of elite families and discarding inferior sugarcane (Saccharum spp.) families could improve sugarcane breeding and selection efficiency. The feasibility of using the method Dynamic Technique for Order Preference by Similarity to Ideal Solution (DTOPSIS) method was explored to identify superior sugarcane families. Data on 5 traits: Brix, millable stalks per stool (MS), stalk diameter (SD), plant height (PH), and percent pith were collected from two family trials having 17 families and two check cultivars at two sites including plant-cane and first-ratoon crops. The rest of the seedlings were planted into field for routine selection in the regular program. The DTOPSIS method calculates a comprehensive index (Ci) which expresses the closeness of a solution to the ideal solution and was used in this study to test the distance of each family to the ideal family. The Ci of the families was compared to the family selection rate in the regular program by determining the selection rate at Stage 1 to Stage 4 for each family in the regular program. The result indicated that the Ci values calculated from family trials were significantly (p<0.01) correlated to the selection rate at Stage 2 (r=0.8059), Stage3 (r=0.7967), and Stage 4 (r=0.8202), and indicating that promising clones were selected from families with higher Ci values in the family trial. Thus, it could be feasible to use DTOPSIS to determine elite sugarcane families and to eliminate inferior families and thereby, increasing the variety selection efficiency.