Kishan Singh

Effect of soil fumigation with vapam on the dynamics of soil microflora and their related biochemical activity

SummaryFungal propagules, in general, were drastically reduced in vapam amended soils. The toxicant from 250 to 1000 ppm was lethal toFusarium spp. Only in the early part of the experiment, higher concentrations of vapam appreciably reduced the population of bacteria and actinomycetes, though later on, their population gradually increased. The numbers of Azotobacter in soil amended with 125, 250 and 500 ppm did not alter appreciably, but their population in treated soils increased over the check on the 45th day. All concentrations of vapam lowered the population of Rhizobia.Vapam produced inhibitory effect on soil nitrification, inhibition period varying with the amount of chemical applied initially. Vapam from 125 to 500 ppm stimulated the ammonification process, while its higher concentration (1000 ppm) produced detrimental effect for 15 days. The toxicant increased CO2 production for first 32 days.Results suggest that extraordinary success of vapam in controlling soil-borne infections of Pythium and Rhizoctonia was not entirely due to its fungicidal action. Partly it was also due to an increase in the population of known antagonists of these pathogens in fumigated soils.

Lime-induced iron chlorosis in sugarcane

Lime-induced chlorosis is a potential problem on most calcareous soils particularly in arid and semi-arid climates affecting most of the plants grown on them. Bicarbonates, phosphates, calcium, iron inactivation in plant tissue and organic anions have been held responsible as the mechanism leading to the disorder which is still not fully understood, and there is a lack of agreement as to the primary factor responsible for lime-induced chlorosis. To date, no hypothesis has adequately explained why chlorosis occurs on some high lime soils and not on others. Likewise, the nutrient ratios, K/Ca, P/Fe and Fe/Mn considered as diagnostic criteria for lime-induced chlorosis, have shown inconsistency. The presence of calcium carbonate, bicarbonate, calcium and imbalance of nutrient cations in the growth medium, injudicious addition of phosphates, quality of irrigation water, and other soil and plant factors have been held responsible for the disorder. Amelioration of lime-induced chlorosis by (i) acidification of calcareous soils, (ii) use of iron salts, (iii) use of synthetic iron chelates, and (iv) by management practices including the selection and development of varieties resistant to lime-induced iron chlorosis, is discussed. Suggestions for future research work are made.

Bio-organic Amendment of Udic Ustochrept Soil for Minimizing Yield Decline in Sugarcane Ratoon Crops under Subtropical Conditions

The effects of subsequent sugarcane ratooning on soil quality and the crop yields under four treatments [an absolute control (T0), application of recommended dose of nitrogen (N)–phosphorus (P)–potassium (K) (T1), application of sulfitation press mud (SPM), a sugar factory by-product (T2), and SPM along with Gluconacetobacter diazotrophicus (Gd, T3)] were evaluated for 7 years. In the control (T0) and NPK-fertilized (T1) plots, an increase in soil compaction (5.4%), decrease in infiltration rate (6.04%), lower microbial activities, and increased soil phenolic contents (72.4%) rendered the nutrients unavailable, leading to significant declines in the crop yields at the rate of 5.47 Mg ha−1 y−1 and 4.67 Mg ha−1 y−1, respectively. The crop yield declined from 53 kg ha−1 in plant crop to 18 kg ha−1 in the sixth ratoon crop under the absolute control. The rates of yield decline, however, were minimized in SPM (T2) and SPM + Gd (T3) plots to 3.54 and 3.51 Mg ha−1 y−1.

Soil-Root Interface Changes in Sugarcane Plant and Ratoon Crops under Subtropical Conditions: Implications for Dry-Matter Accumulation

Poor sugarcane ratoon yields in the subtropics are responsible for decrease in overall productivity and poor sugar recovery. The present work is an attempt to assess reasons for decline in crop productivity despite providing adequate inputs. The simultaneously initiated plant and ratoon crops were compared for dry-matter accumulation and its distribution pattern in relation to changes in soil-root interface environment. In spite of well-established root system and advanced sprouting and tillering during the formative phase, dry-matter accumulation and nutrient uptake were low in a ratoon crop and were more apparent 120–210 days after planting. This decrease in nutrient uptake was due to declines in soil cation-exchange capacity, nitrate reductase (NR) activity in vivo by 19.4 and 25.9 percent, and increase in percentage leakage by 11.26 percent. These alterations at the soil-root interface in ratoons functioned as barriers for nutrient uptake and affected overall physiological growth and dry-matter accumulation adversely.

Pathogenicity and Histopathology of Hoplolaimus Indi Cus On Sugarcane

Sugarcane growth was markedly reduced when 1,000 Hoplolaimus indicus were added to plants in a 15 cm diameter pot. At this population density, the root system of the plant was reduced and young laterals had reddish-brown lesions. Histopathology of these roots indicates that the nematodes penetrated cells with the aid of their stylets. These damaged cortical cells were filled with a reddish-brown substance. The main body of the nematode was in the cortical cells and oriented towards the root tip and vascular system.