Chilean Journal of Agricultural Research

ABSTRACT Primary risk to rice (Oryza sativa L.) production is salinity intrusion and water scarcity, leading to a shortage of irrigation water and yield reduction. We examine the impact’s effects of alternate wetting and drying (AWD) vs. continuous flooding (CF) and microbe application on yields of three rice cultivars (Ciherang, Inpari 34 Salin Agritan, Inpari 35 Salin Agritan) grown under slight and moderate soil salinity in the dry season (DS) 2017 and 2018. Under slight soil salinity, AWD and CF had nonsignificant difference in grain yield. Under a moderate soil salinity level, there was a substantial decrease in grain yield (8.2%), number of productive tillers, seeds panicle-1, and weight of 1000 grains with the plants grown under AWD. Increased soil salinity levels resulted in lower yield reduction with microbial than without microbial treatments. ‘Ciherang’ showed superiority over ‘Inpari 34’ and ‘Inpari 35’ under AWD at slight soil salinity. However, the yield reduction in the moderate salinity level was more remarkable for ‘Ciherang’ (18.1%) than ‘Inpari 34’ and ‘Inpari 35’ (9.7%) as salinity-tolerant varieties. The AWD used almost one-third less irrigation supplement than CF. This greatly assists small farmers in reducing the additional cost of pumping water. On average, AWD improved total water productivity by 32.7% under slight and 20.4% under moderate soil salinity over CF. Here, we lay out the potential for small farmers in slight salinity lowlands areas of the northern coast of Java to apply AWD during the DS. Farmers could manage water efficiently to prevent further yield loss and improve farm profitably.

ABSTRACT Rice-fish integrated farming model has become one of the main directions for sustainable agricultural development due to its good ecological and environmental effects and ability to produce green rice (Oryza sativa L.) that meets the market’s food safety needs. Its study characterizes soil bacterial community structure in this model for the improvement of planting and breeding technology and realization of ecological regulation. The community structure of soil microorganisms was compared between two models of rice-frog (black-spotted pond frog; Pelophylax nigromaculatus Hallowell, 1861) co-cropping (DW) and rice monoculture (DD) at tillering stage, full heading stage and maturity stage, to accumulate data for research on ecology of rice-frog integrated farming and provide a theoretical basis for optimization of this production technology. Main bacterial phyla occurring in rhizosphere soil of rice fields in both models under three stages were Proteobacteria, Chloroflexi, Acidobacteriota, Bacteroidota, Firmicutes, Actinobacteriota, Nitrospirota and Desulfobacterota. Compared to DD, DW group had more Actinobacteriota in the dominant phyla at maturity and less Desulfobacterota throughout the growth period. The main dominant genera were norank_f_Anaerolineaceae, norank_f_norank_o_norank_c_Thermodesulfovibrionia, norank_f_norank_o_SBR1031, norank_f_norank_o_Vicinamibacterales, unclassified_k_norank_d_Bacteria and Thiobacillus. There were five categories with significant difference, norank_f_Anaerolineaceae, norank_f_norank_o_SBR1031, norank_f__norank_o_Vicinamibacterales, Thiobacillus and unclassified_k_norank_d_Bacteria; all were higher in relative abundance in DW than in DD group. It indicates that rice-frog crop model promotes the growth of these five types of bacteria, which have a boosting effect on rice growth. The bacterial Chao index and Shannon index of rhizosphere soil of rice field increased after introduction of frog in DW group. The two models showed less variation in soil bacterial community structure in root system from full heading to maturity stage, and co-cropping model showed less variation compared to rice monoculture.

ABSTRACT The combined use of a microbial additive and a chemical additive in sorghum (Sorghum bicolor (L.) Moench) silages would reduce fermentation losses, favoring aerobic stability by modulating a favorable microbiome to control those losses. The purpose of this study was to evaluate the action of Lactobacillus buchneri and sodium benzoate on the fermentative profile, bacterial taxonomic diversity and aerobic stability of sorghum silages at different fermentation times. A completely randomized experimental design was adopted in a 4 × 4 factorial scheme, in order to evaluate four additives in sorghum silage (Control treatment, L. buchneri, sodium benzoate and L. buchneri combined with sodium benzoate) and four opening times (30, 60, 90 and 120 d fermentation), in five replicates. Silages inoculated with sodium benzoate showed higher pH values (3.70) at 90 d of fermentation, not differing (P > 0.05) from control (CTR) silage and the other silages. The largest lactic acid bacteria populations were observed at 120 d of fermentation in the silages inoculated with L. buchneri (9.06) followed by the silages inoculated with sodium benzoate and with the combination L. buchneri + sodium benzoate (8.37 and 8.85 log CFU, respectively) at 90 d of fermentation. For gas losses, in which silage treated with sodium benzoate showed lower values, with an average of 0.72% DM. The silages presenting a high DMR standard, ranging from 94.6% to 98.0%, with the exception of the CTR silages. Silages treated with L. buchneri showed higher values (98%) for the occurrence of the genus Lactobacillus in both fermentation times. The combined action of L. buchneri and sodium benzoate kept the Lactobacillus population stable at 30 and 120 d of fermentation. The combination of L. buchneri and sodium benzoate improved the fermentative profile and chemical composition of sorghum silages, reducing losses and increasing aerobic stability after 120 d of fermentation.

ABSTRACT The Peruvian Amazon has been significantly affected by land use and climate change, decreasing decomposition processes, which cause a significant depletion of soil C stocks. In this study, we estimated soil organic C (SOC) mediated by different plant covers in coffee (Coffea arabica L.) plantations and secondary forests in several districts of the San Martín Region, Peru. We calculated the critical threshold, saturation point, and the organic C deficit of these Amazonian soils. The association between geography, soil physical-chemical characteristics, and SOC was estimated through principal component analysis. Across all sites of the study, SOC stock had an average value of 69.19 t ha-1, with 48.95 t ha-1 constituting inorganic C. The highest SOC stock (225.28 t ha-1) was observed under secondary forest in the Jepelacio district. The SOC stocks were positively correlated with altitude and CaCO3 content only in secondary forests. The current measured amount of organic C within 15 cm soil depth was 28.5 g C kg-1, which is very low and close to the critical threshold (20.6 g C kg-1) -estimated based on its clay and silt contents. Our SOC stocks measurements indicated a worrisome situation, as they are close to the critical threshold, which exposes this area to a greater and stronger degradation.

ABSTRACT The root-knot nematode (Meloidogyne spp.) causes losses of up to 68% of tomato (Solanum lycopersicum L.) production, management practices are limited and toxic chemicals are mostly used. An integrated management alternative was evaluated based on the antagonist effect of native bacteria of the genus Bacillus on the nematode using four tomato germplasms, two commercial (susceptible and tolerant) and two wild (IAC 1687 and COLY 007). In the in vitro phase, strains B. infantis (GIBI 177), B. altitudinis (GIBI 187), B. pumilus (GIBI 195), B. amyloliquefaciens (GIBI 200) and B. pumilus (GIBI 206) were evaluated and the percentage of inhibition of nematode egg hatching at 9 d after inoculation and the percentage of mortality in juveniles at 72 h after incubation were determined. The results showed that all native strains presented a control effect under controlled conditions, but B. infantis being the bacterium with the highest selection index (0.65). In the field phase, a split-plot design was established, the main plot being the four-tomato genotype and the secondary plot the bacillus strain, and the percentage of severity, number of eggs and juveniles were evaluated. The tomato genotype with the best response to Meloidogyne spp. attack was IAC 1687, when obtaining values of 2088.8 ± 599.1 individuals 100 g-1 root. The bacterium that presented the best interaction with 3 of the 4 genotypes evaluated was B. pumilus (GIBI 206), in IAC 1687 with 1731.33 ± 1382. 57 individuals 100 g-1 root, in the resistant genotype with 16627 ± 4588.1 individuals 100 g-1 root and in the susceptible genotype with 3303.83 ± 1256.25 individuals 100 g-1 root. This study reports the use of tomato genetic resources and antagonist bacteria as a potential integrated management of the root-knot nematode.