Soil enzymatic activity as affected by long term application of farm yard manure and mineral fertilizer under a rainfed soybean–wheat system in N-W Himalaya

Long-term experimental sites are expected to provide important information regarding soil properties as affected by management practices. This study was designed to examine the effects of continuous fertilization, and manuring on the activities of enzymes involved in mineralization of C, N, and P on a long term (33 years) field trial under sub-temperate conditions in India. Treatments at the site included application of recommended doses of nitrogen and phosphorus (NP), nitrogen and potassium (NK), nitrogen, phosphorus and potassium (NPK), farmyard manure (FYM) with N (N + FYM), FYM with NPK (NPK + FYM) and un-amended control (C). The study was done under rainfed soybean–wheat rotation. Manure application increased soil carbohydrate, dehydrogenase, acid and alkaline phosphatases, cellulase, and protease activity significantly. Urease activity was not influenced by the manure treatment and the activity was highest in controls. Both acid and alkaline phosphatase activities were negatively influenced by chemical fertilizer treatment. Almost all the enzymes studied were significantly correlated with soil C content. The results suggest that application of FYM directly or indirectly influences the enzyme activity and it in turn regulates nutrient transformation.     

Critical carbon inputs to maintain soil organic carbon stocks under long‐term finger‐millet (Eleusine coracana [L.] Gaertn.) cropping on Alfisols in semiarid tropical India

Enrichment of soil organic carbon (SOC) stocks through sequestration of atmospheric CO₂ in agricultural soils is important because of its impacts on adaptation to and mitigation of climate change while also improving crop productivity and sustainability. In a long‐term fertility experiment carried out over 27 y under semiarid climatic condition, we evaluated the impact of crop‐residue C inputs through rainfed fingermillet (Eleusine coracana [L.] Gaertn.) cropping, fertilization, and manuring on crop yield sustainability and SOC sequestration in a Alfisol soil profile up to a depth of 1 m and also derived the critical value of C inputs for maintenance of SOC. Five treatments, viz., control, farmyard manure (FYM) 10 Mg ha^–1, recommended dose of NPK (50 : 50 : 25 kg N, P₂O₅, K₂O ha^–1), FYM 10 Mg ha^–1 + 50% recommended dose of NPK, and FYM 10 Mg ha^–1 + 100% recommended dose of NPK imposed in a randomized block design replicated four times. Application of FYM alone or together with mineral fertilizer resulted in a higher C input and consequently built up a higher C stock. After 27 y, higher profile SOC stock (85.7 Mg ha^–1), C build up (35.0%), and C sequestration (15.4 Mg C ha^–1) was observed with the application of 10 Mg FYM ha^–1 along with recommended dose of mineral fertilizer and these were positively correlated with cumulative C input and well reflected in sustainable yield index (SYI). For sustenance of SOC level (zero change due to cropping) a minimum quantity of 1.13 Mg C is required to be added per hectare per annum as inputs. While the control lost C, the application of mineral fertilizer served to maintain the priori C stock. Thus, the application of FYM increased the C stock, an effect which was even enhanced by additional amendment of mineral fertilizer. We conclude that organic amendments contribute to C sequestration counteracting climate change and at the same time improve soil fertility in the semiarid regions of India resulting in higher and more stable yields.     

Buffalo heifers selected for lower residual feed intake have lower feed intake,better dietary nitrogen utilisation and reduced enteric methane production

This study was conducted to evaluate the utilisation of the residual feed intake (RFI ) as a feed efficiency selection tool and its relationship with methane emissions. Eighteen Murrah buffalo (Bubalus bubalis ) heifers were fed ad libitum with total mixed ration (TMR ) for 120 days. Based on linear regression models involving dry matter intake (DMI ), average daily gain (ADG ) and mid‐test metabolic body size (MBW ^0.75), heifers were assigned into low and high RFI groups. The RFI varied from ?0.09 to +0.12 kg DM /day with average RFI of ?0.05 and 0.05 kg DM /day in low and high RFI heifers respectively. Low RFI heifers ate 11.6% less DM each day, yet average daily gain (ADG ) and feed utilisation were comparable among low and high RFI groups. Low RFI heifers required significantly (p  < .05) less metabolizable energy for maintenance (ME m) compared to high RFI heifers. Apparent nutrient digestibility showed non‐significant difference (p >  .05) among low and high RFI groups. Although the nitrogen balance was similar among heifers of low and high RFI groups, nitrogen metabolism was significantly higher (p  > .05) in high RFI heifers. Comparison of data from heifers exhibiting the low (n  = 9) and high (n  = 9) RFI showed that the low RFI heifers have lower enteric methane production and methane losses than high RFI heifers. In conclusion, results of this study revealed that selection of more efficient buffalo heifers has multiple benefits, such as decreased feed intake and less emission of methane.     

Influence of irrigation frequencies and phosphate fertilization on actual evapotranspiration rate, yield and water use pattern of rajmash (Phaseolus vulgaris L.)

The hypothesis was tested, whether soil wetness and phosphorus status could regulate the evapotranspiration rate (ET_R), which is of special interest in the lower Gangetic Plain. Rajmash was grown during November-February of 2003-2004 and 2004-2005 on a sandy loam soil, and was irrigated when cumulative pan evaporation (CPE) attained the value of 33 mm (CPE₃₃); 44 mm (CPE₄₄) and 66 mm (CPE₆₆). Four levels of phosphate application were 0 kg P₂O₅ ha⁻¹ (P₀); 30 kg P₂O₅ ha⁻¹ (P₃₀); 60 kg P₂O₅ ha⁻¹ (P₆₀) and 90 kg P₂O₅ ha⁻¹ (P₉₀). Seed yield under CPE₃₃ was 1.37 Mg ha⁻¹ and reduced by 18% and 35%, respectively under CPE₄₄ and CPE₆₆. Continuous increasing trend in yield was recorded with an increase in phosphate level (PL). Irrespective of growth stages, similar trends were recorded for leaf area index (LAI). Maximum variation in LAI among the treatments was recorded at 60 days after sowing. On average, actual ET_R was 1.37 mm day⁻¹ under CPE₃₃ and declined by 13% and 16% under CPE₄₄ and CPE₆₆, respectively. Variation in ET_R under different PL was highest under CPE₃₃ and lowest under CPE₄₄. Except P₉₀, irrespective of PL, highest value of water use efficiency (WUE) was obtained under CPE₄₄. However, magnitude of net evapotranspiration efficiency (WUE_ET) and irrigation efficiency (WUE_I) attained the highest level under CPE₃₃ regime. All water use indices showed an increasing trend with the increase in phosphate level from 0 to 90 kg ha⁻¹. Impact of phosphorus on various parameters was pronounced under CPE₃₃.     

Simultaneous detection of stone fruit tree viruses by one-step multiplex RT-PCR

A protocol of multiplex RT-PCR in a one-tube system for the detection of the most common stone fruit trees viruses [e.g., plum pox virus (PPV), prune dwarf virus (PDV), and Prunus necrotic ringspot virus (PNRSV)], including the internal control of NADH dehydrogenase subunit 5 (nad5) gene are described here. The method specificity was tested on more than 80 different samples with various isolates and strains of the viruses. It showed that the targeted viruses produced the expected amplicons, whereas all other related viruses produced only the nad5 internal control amplicon. The method sensitivity was evaluated by comparing it with Simplex RT-PCR with the same primers; no significant differences in detection limits were recorded. Furthermore, the competitiveness of the primers in the assay was tested by serial RNA dilutions of samples with mixed and single infections. The least competitive was the internal control nad5 gene primer pair; therefore, there is a reduced risk of false negatives as all the other primers tend to be more efficient in the given primer cocktail than in the primers for internal control.     

Karyotype analysis and chromosomal evolution in Asian species of Corchorus (Malvaceae s. l.)

Here, we report the karyotypes and mean haploid idiograms of the ten Asian Corchorus species (2n = 2x = 14). Chromosomes were small, with a mean chromosome length of 2.30 μm. The largest chromosome was recorded in C. pseudo-olitorius (3.50 μm) and the shortest in C. pseudocapsularis (1.60 μm). The karyotypes of the two cultivated species (C. capsularis and C. olitorius) and C. pseudo-olitorius were the most diverse and specialized, whereas those of C. depressus and C. trilocularis were the least diverse. C. fascicularis had the most asymmetrical and C. urticifolius the most symmetrical karyotypes. An increase in genome size was accompanied by increasing karyotype diversity in terms of morphologically distinct chromosome types and interchromosomal asymmetry, with uneven distribution of additional DNA throughout the karyotype. A positive correlation between interchromosomal asymmetry and dispersion index suggested that size differences between chromosomes were mainly associated with karyotype asymmetry. Karyotypes of the Corchorus species became progressively asymmetrical in the course of evolution. Relationships among the ten Corchorus species were defined by using a neighbor-joining tree inferred from inter-simple sequence repeat data. C. fascicularis and C. pseudocapsularis, with shorter karyotypes and smaller genomes, were closely related to C. pseudo-olitorius and C. capsularis, respectively, which were characterized by relatively longer karyotypes and larger genomes. However, the two cultivated species with different levels of interchromosomal asymmetries, dispersion indices and genome sizes were distantly related. Taking this molecular evidence into consideration, we have discussed chromosomal evolution in relation to karyological data including genome size.     

LONG‐TERM MANURING AND FERTILIZER EFFECTS ON DEPLETION OF SOIL ORGANIC CARBON STOCKS UNDER PEARL MILLET‐CLUSTER BEAN‐CASTOR ROTATION IN WESTERN INDIA

Soil organic carbon (SOC) pools are important for maintaining soil productivity and reducing the net CO₂ loading of the atmosphere. An 18‐year old long‐term field experiment involving pearl millet‐cluster bean‐castor sequence was conducted on an Entisol in western India to examine the effects of chemical fertilizers and manuring on carbon pools in relation to crop productivity and C sequestration. The data showed that even the addition of 33.5 Mg ha⁻¹ C inputs through crop residues as well as farm yard manure could not compensate the SOC depletion by oxidation and resulted in the net loss of 4.4 Mg C ha⁻¹ in 18 years. The loss of SOC stock in the control was 12 Mg C ha⁻¹. Conjunctive use of chemical fertilizers along with farm yard manure produced higher agronomic yields and reduced the rate of SOC depletion. The higher average seed yields of pearl millet (809 kg ha⁻¹), cluster bean (576), and castor (827) over six cropping seasons were obtained through integrated use of fertilizers and manure. For every Mg increase in profile SOC stock, there was an overall increase of 0.46 Mg of crop yield, comprising increase in individual yield of pearl millet (0.17 Mg ha⁻¹ y⁻¹ Mg⁻¹ SOC), cluster bean (0.14) and castor (0.15). The magnitude of SOC build up was proportional to the C inputs. Carbon pools were significantly correlated with SOC, which increased with application of organic amendments. Threshold C input of 3.3 Mg C ha⁻¹ y⁻¹ was needed to maintain the SOC stock even at the low antecedent level. Copyright © 2011 John Wiley & Sons, Ltd.     

Direct monitoring of Rhizobium sp. (Cicer) in nodules and soil using lac Z fusions

We constructed lacZ fusions in Rhizobium sp. (Cicer) by random Tn5-lacZ mutagenesis. The lacZ⁺ fusants formed blue colonies on a Rhizobial minimal medium containing 5-bromo-4-chloro-3-indolyl--D-galactopyranoside (X-gal). Rhizobium sp. (Cicer) fusant HSL-2 was identified in nodules and soil in a mixed population on the basis of the lacZ⁺ phenotype. Nodule occupancy of inoculated Rhizobium sp. (Cicer) HSL-2 (lacZ⁺) was assessed by directly streaking the nodule sap on X-gal plates. This method revealed differences between rhizobia carrying identical antibiotic markers. The rhizobial population in soil was estimated by direct plate counts using a medium containing X-gal. Introduction of lacZ into the Rhizobium sp. thus provided a simple and direct method for identifying strains from nodules and soil.