A field experiment was conducted on a cropping sequence pattern of
two legume crops to avoid the residual effect of the grown crop at the next
season, i.e., peanut as summer crop (Arachis hypogaea, Giza 5) followed
by faba bean as a winter one (Vicia faba, Giza 2) grown on sandy soils
under sprinkler irrigation system at El Ismailia Agricultural Research
Station during the agricultural growing season of 2002/2003. The current
study aims to identify the direct and residual beneficial effects of applying
some organic polymers (carboxy methyl cellulose-CMC and
polyvinylacetate-PVAc) and humic acids-(HA) on some hydrophysical
and fertility status of sandy soil (bulk density, total porosity, hydraulic
conductivity, moisture constants and nutrients retained) at elongation
stage of vegetative growth as well as vegetative growth, yield and its
attributes of the studied two crops, i.e., peanut (seed & foliage yields,
harvest index, weight of 100 seed, seed oil %, protein % and uptake
nutrient contents of N, P, K, Fe, Mn and Zn) and faba bean (plant height,
No. of branches or leaves/plan, dry matter of stem or leaves, seed and
foliage yields, harvest index, 100 seed weight, protein and uptake nutrient
contents). The applied rates of organic polymers were 2 % w/w as
individual or combined treatments with humic acid (solid K-humate at a
rate of 50 mg kg-1), then were thoroughly mixed with the 15 cm soil
surface.
The results obtained indicated that the applied organic polymers and
humic acid as either individual or in combined treatments (HA+PVAc and
HA+CMC) showed significant and positive increases in both soil
characteristics and the grown peanut parameters under investigation, with
a significant superiority for the combined treatments. The beneficial
influence was extended in a parallel trend to the next winter crop of faba
bean as a residual effect, but with useful-less for all the previous studied
soil characteristics and plant parameters.
It is evident that the applied organic amendments, either as
individual or together treatments, were achieved many of the beneficial
effects on soil hydrophysical and fertility status as well as plant
parameters, since humic acid acted like plant growth hormones. In
addition, organic polymers (carboxymethylcellulose and polyvinylacetate)
partially capable to retain water and nutrients for growing plants, where it
would act as complexing agents, this minimizes the loss of nutrients by
leaching. Thus, these chelating gents, through OH and COOH as active
groups for micronutrients and water molecules, are considered as a
storehouse with easily mobile or available to uptake by plant roots, and in
turn reflected positively on development of yield and its attributes for both
studied peanut and faba bean crops.