Soil organic carbon and iron oxides affects soil aggregate stability under straw returning and potassium fertilizer in a rice--rape cropping system

Soil organic carbon (SOC) and iron (Fe) oxides are known to affect the formation and stability of soil aggregates. However, the effects of SOC and Fe oxides on soil aggregates stability under straw returning and potassium (K) fertilizer application in paddy–upland rotation systems are less well-studied. This study primarily investigated soil aggregates dynamics and their stability indices (mean weight diameter, MWD; geometric mean diameter, GMD), and soil binders (SOC and iron oxides) after rice and rape harvests under four treatments: F1，mineral nitrogen (N) and phosphorus (P) fertilizer; F2, mineral NPK fertilizer; F3, mineral NP fertilizer with straw returning; F4, mineral NPK fertilizer with straw returning in rice–rape cropping system. Straw returning treatments (F3 and F4) significantly (P <0.05) increased MWD and GMD, but the effect of K is not obvious. The soil aggregates stability was higher after the rape harvest than rice harvest, but SOC content was the opposite. Straw input can increase the contents of SOC, alkane-C and aromatic-C concentrations, especially in >0.25 mm aggregates. Long-term straw incorporation significantly increased the amorphous (Feo) and complex iron oxides (Fep) concentrations. SOC and Fep in bulk soil and >5 mm aggregates were significantly related with MWD, and significant relationship was observed between MWD and Feo in <5 mm fractions. Thus, the high levels of SOC, alkane-C, Feo and Fep in soil after straw returning were responsible for the aggregate stability, but the effect of potassium application is not obvious in a rice–rape cropping system.

Responses of Garlic Quality and Yields to Various Types and Rates of Potassium Fertilizer Applications

Potassium (K) is a critical plant nutrient that determines quality in a myriad of crops and increases production yields. However, excessive application of various types of K fertilizers can decrease both the food quality and yields, which translates as economic losses and food safety issues. The objectives of this study were to 1) elucidate the impacts of different application rates of various K fertilizers on garlic, with the aim to identify the optimal and most economical K fertilizer dosage and 2) compare the effects of applying two common K fertilizers (KCl and K2SO4) on garlic, to determine the optimal combination. From 2018 to 2020, we utilized two distinct K-fertilized fields to conduct our experiments. The results revealed optimal KCl fertilization increased the biomass and vegetation index in garlic, and promoted the transfer of nitrogen, phosphorus, and potassium nutrients from the stem and leaf to bulb, thereby increasing bulb production. The application of KCl fertilizer increased the number of cloves, the diameters of the cloves and bulbs, and reduced variations in bulb size. In addition, the application of KCl fertilizer improved the nutritional quality (Vitamin C, soluble sugar, soluble protein, and allicin) of the garlic and reduced the accumulation of nitrate. However, excessive KCl fertilizer cause decreased yields, appearance traits, and nutritional quality. Applying the same rate of K fertilizer in the form of K2SO4 in isolation increased the garlic yield by only 0.1% to 22.5% when compared with KCl fertilizer. However, the results were not always significant. In this study, the highest yields, appearance traits, and nutritional quality were achieved with the ratio of K2SO4: KCl = 3:1. Consequently, to ensure the highest economic value (considering the market prices of K fertilizer, garlic sprouts, and bulbs), the authors recommend a K fertilizer rate of 252.5 kg·ha−1 K2O, with K2SO4 accounting for 61.6% for garlic production in field.

Alternative products to control late season diseases in soybeans

ABSTRACT: In the last crop seasons, the complex of late season diseases (CLSD) of soybean (Glycine max L. (Merrill)), has been causing considerable reductions in the crop yield. Currently, there are no cultivars resistant to all pathogens that causes CLSD. The present study evaluated the effect of applying the acibenzolar-S-methyl resistance inducer, alternative products and fungicide on the severity of CLSD in the soybean cultivar BMX Potência RR during the 2013/2014 and 2014/2015 crops, in the field. The treatments for the experiments were: 1 - control (water); 2 - acibenzolar-S-methyl; 3 - calcium; 4 - micronutrients: copper, manganese and zinc; 5 - micronutrients: manganese, zinc and molybdenum; 6 - nitrogen-potassium fertilizer; 7 - Ascophyllum nodosum and 8 - azoxystrobin + cyproconazole with the addition of the adjuvant. Four applications of alternative products and two of fungicide were carried out in both harvests. A diagrammatic scale assessed the severity of CLSD at the phenological stage R7.1. The acibenzolar-S-methyl resistance inducer, alternative products (macro and micronutrients) and A. nodosum had no effect on the severity of CLSD in the two harvests. The fungicide (azoxystrobin + cyproconazole) reduced the severity of CLSD and prevented damage to productivity in both experiments.

Design and Experimental Research of Variable Formula Fertilization Control System Based on Prescription Diagram

In order to solve the problems such as the inability to automatically mix a variety of solid fertilizers and the unreasonable fertilizer amount, improve fertilizer utilization, and reduce production costs, this study designs a variable formula fertilization control system based on a prescription diagram, including pressure sensor, speed sensor, servo motor, fertilizer discharge actuator, Programmable Logic Controller (PLC controller), vehicle control terminal, etc. Based on pre-loaded soil prescription diagram and combining fertilizer pressure and ground wheel speed detection information, the system obtained a formula fertilization control strategy through calculation to realize the function of fast and automatic formula of nitrogen, phosphorus, and potassium fertilizers and precise variable fertilization. The experimental study on the performance of the variable formula fertilization control system showed the following: the measurement error range of the pressure sensor was 0.005~0.03%; the relationship between the motor speed and the amount of nitrogen, phosphorus, and potassium fertilizer discharged was calibrated. Three gears were established for the motor speed: low (10 r/min), medium (30 r/min), and high (50 r/min); the measurement accuracy of the speed sensor was above 98%. The test verified that the control accuracy of the variable formula fertilization system reached more than 95%, which met the requirements of fast automatic formula and precise variable fertilization and had good practicability and economy.

The Growth and Production of Three Sweet Potato Varieties as Affected by Dosage of Potassium Fertlizer on the Ultisols of Bengkulu Province

This study aims to study the interaction between varieties and the correct dose of potassium fertilizer, determine the right dose of potassium fertilizer and the appropriate variety of sweet potato in Ultisol. In this study, the research design used was a completely randomized block design (RAKL) with two (2) factors with three replications. The first factor is three varieties of sweet potato, namely Cilembu, Atin 3, and Beta 1. The second factor is the dose of KCl fertilizer which consists of 4 levels of dosage, namely 0 kg ha-1, 150 kg ha-1, 300 kg ha-1, and 450 kg ha-1 KCl fertilizer. The results showed no significant interaction between the dose of KCl fertilizer and the three varieties of sweet potato. The Antin 3 variety produced the most extended tendril length compared to the other two varieties. The lowest number of branches was produced by Beta 1 variety. The Cilembu variety produced the most significant tuber weight per plot and estimated weight per plot. The Cilembu variety is proven to have the highest level of sweetness.

Growth, Fruit Yield and Proximate Composition Responses of Hot Pepper (Capsicum annuum L; Rodo Variety) to Potassium Fertilizer Application at Ado-Ekiti, Nigeria

Potassium (K) fertilizer application, as a component of the improved technologies necessary to maximize crop yield and quality, is often used to correct the plant, soil and environmental factors that limit K availability. The effects of 0, 30, 60 and 90 kg K2O ha-1 were studied on hot pepper (Capsicum annuum L; Atarodovariety) in 2014 and 2015 on the Teaching and Research Farm, Ekiti State University, Ado-Ekiti Nigeria in a Randomized Complete Block Design with four replicates. Each K rate was mixed with 75 kg N and 25 kg P2O5 ha-1 and applied 2 weeks after transplanting 5-week old seedlings spaced 60 cm × 40 cm apart. The data of growth parameters were collected at 2 weeks after treatment (WAT) and fortnightly till 10 WAT, number and weight of ripe fruits and fruit proximate composition. The plant height, number of leaves, leaf area and dry matter increased with age and K rates to highest values at 10 WAT and 90 kg K2O ha-1 in both years. The number of fruits, fruit and seed yield ha-1, fruit size, fruit length and breadth and pericarp thickness increased linearly from the control to the highest values at 90 kg K2O ha-1.The number of fruits and yield at 90 kg K2O ha-1 were 1.253×106, 14.24 t ha-1; and 3.73×106, 14.94 t ha-1 in 2014 and 2015, respectively but the 60 kg K2O ha-1 gave the highest agronomic efficiency. The slight increase in fruit moisture content would not predispose fruits to deterioration while the crude protein and fat, carbohydrate and ash contents, vitamin C and mineral nutrients increased significantly making K application necessary to balance the fertilizer protocol for optimum hot pepper production.

Influence of Rainfall and Water Deficit in the Efficiency of Potassium Fertilizer on the Productivity of Oil Palm (Elaeis Guineensis Jacq.), Grown in Southeastern Côte d’Ivoire

In Côte d’Ivoire, palm oil occupies a preponderant position in agricultural production, in the economy, as well as consumer fats. Yield remains low, even with improved plant material being popularized whose productivity is estimated at more than 25 tons/ha/year. Trials have been set up in La Mé and Ehania (South-east Côte d’Ivoire), to help improve oil palm productivity, through a comparative study of the efficiency of potassium fertilization applied according to the locality. The experiments were conducted in Fisher blocks, including 5 treatments and 4 repetitions. The treatments included 5 doses of potassium fertilizer (T1, T2, T3, T4, T5) corresponding, respectively, to 1; 1.5; 2; 2.5; 3 kg KCl/tree/year. The results showed that the rainfall recorded in the locality of Ehania was significantly higher than that of La Mé. The average annual rainfall was 2000 mm of water in Ehania against, approximately, 1700 mm of water in La Mé. The yield and its components (weight of the bunch and number of bunches) were gradually improved according to the locality of cultivation by the different doses of fertilizer applied. This improvement was significantly higher on the Ehania plantation compared to that of La Mé. This improvement was approximately 30% and 27% compared to the standard dose of 1 kg KCl/tree/year, respectively, in Ehania and La Mé. It appears that the locality intervenes in the efficiency of potassium fertilizers, in the improvement of yield and its components. Rainfall appears, as, a main factor of productivity observed on the plot of the oil palm. Strict compliance with the choices of suitable areas, combined with reasoned potassium fertilization, will allow a better expression of the production potential of new oil palm plant material, currently being popularized.

The Effect of Foliar Application of K2SO4 or KH2PO4 on Skin Color of the ‘Kyoho’ Grape

Anthocyanins in red grape skin have a positive effect on fruit color and human health. The effect of foliar potassium application on anthocyanin accumulation in grape skin is not well understood. The study aimed to better understand the mechanism of anthocyanin accumulation in grape skin in response to foliar sprays of K2SO4 and KH2PO4. In this study, we investigated the effects of foliar application of KH2PO4 (T2), K2SO4 (T1) and distilled water (CK) on the skin color of ‘Kyoho’ grapes at mid-ripe and mature stages. At 90 and 110 days after full bloom (DAFB), T2 had the greatest total soluble solids (TSS), flavonoid and total anthocyanin contents, followed by T1 and CK. At two stages, the titratable acid content decreased and the juice pH increased under T2 treatment relative to CK. T1 and T2 had lower lightness (L*) than CK, and the color index of red grapes (CIRG) under T1 and T2 increased at two stages compared to CK. KEGG metabolic pathway analysis revealed that flavonoid biosynthesis was the most significantly enriched pathway in CK vs. T2 at 90 and 110 DAFB. At 90 DAFB, T2 had higher expressions of phenylalanine ammonia-lyas (PAL), cytochrome P450 CYP73A100 (CYP73A), 4-coumarate: CoA ligase (4CL), chalcone synthase (CHS), flavanone 3-dioxygenase-like (F3H) and UDP glucose: flavonoid 3-o-glucosyl transferase (UFGT) than CK and T1. Foliar application of potassium fertilizer may accelerate anthocyanin accumulation by altering the transcript levels of PAL, CYP73A, 4CL, CHS, F3H, and UFGT of the flavonoid biosynthesis.