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Abstract
5. Two field successive experiments were carried out employing a sandy soil to investigate the possibility of maximizing the organic farming productivity, where nutrients content of experimental plants i.e peanut (Arachis hypogaea L., cv Giza 5) and pepper (Capsicum annum L., cv Marrkony) were estimated
І. Peanut experiment:
A field experiment was conducted to evaluate productivity and nutrients content of peanut under organic farming system. Treatments representing all combinations of compost (10 and 15 ton.fed-1) and P enrichment rates (0, 17.6, 26.4 and 35.2 kg P fed-1) in randomized complete block design were replicated three times. Obtained results could be summarized as follows:
1. Response of peanut yield and yield components to compost and P enrichment rate:
Increasing the applied compost rate increased both straw and pod yield while root dry matter was significantly reduced. All the other parameters were not significantly affected with the rate of applied compost.
Phosphorus application induced significantly and gradually up to RPER3 all the tested parameters of yield and yield components except the stem dry weight, which was maximized under RPER3.
The interaction effect of added N and P, increasing P enrichment rate under both compost rates increased yield and yield components.
2. Response of nutrients content in peanut to compost and P enrichment rate:
At the maturity stage, the higher rate of added compost increased the content of N, P and K in root, stem, leaf and kernel of peanut. The P enrichment induced the content of different tested nutrients in all peanut organs except N in stem which significantly decreased under any rate of added P.
The highest rate of added compost yielded always higher values of Fe, Zn and Mn content in peanut leaf or kernel. Micronutrients were increased regularly (Zn and Mn) or irregularly (Fe) due to P application being maximized under RPER4 in kernel.
Under the lower compost rate, significantly increased N content of root, stem, leaf and kernel by increasing P enrichment rate. Under the higher compost rate the N content of stem and root was significantly decreased by increasing P enrichment rate. Increasing P enrichment rate under both compost rates increased P content of all peanut organs. Potassium content of root and kernel increased under lower compost with increasing P enrichment rate; but K content of stem and leaf decreased under higher compost rate with increasing P enrichment rate. Iron, Zn and Mn content of leaf and kernel increased under higher compost rate and when P enrichment rate increased.
At maturity stage of peanut plants, N content in stem and root, opposite to leaf and kernel, decreased under organic farming compared to conventional farming. However, both of P content in stem, root, leaf and kernel as well as K content in stem, root and leaf (opposite to kernel) increased under organic farming in comparison with the conventional farming. The content of Fe and Zn opposite to Mn increased under conventional farming compared with organic farming.
3. Response of nutrients uptake in peanut to compost and P enrichment rate:
The higher rate of added compost increased the uptake of N, P and K in different organs of peanut (root, stem, leaf and kernel) significantly in most cases except P uptake was decreased significantly in root.
Phosphorus uptake increased in all peanut organs gradually as the rate of P enrichment increased. Nitrogen uptake gradually increased due to P application up to RPER4 in peanut stem and kernel, up to RPER3 in root and leaf. Potassium uptake increased gradually with increasing the rate of applied P up to RPER3 in peanut stem, leaf and kernel but up to RPER4 in root.
Under both compost rates, significantly increased N and P uptake of root, stem, leaf and kernel by increasing P enrichment rate, while K uptake significantly increased in root up to RPER3; but K uptake increased significantly in stem, leaf and kernel up to the RPER4.
Both N and P uptake in stem and root, opposite to leaf and kernel, decreased under organic farming compared to the conventional farming. However, K uptake in stem and leaf, opposite to root and kernel increased under organic farming in comparison with the conventional farming.
The high rate of compost yielded always higher values of micronutrients uptake in peanut leaf or kernel, however these increments were significant for Fe, Zn and Mn in plant leaf, but the increments were not significant for Fe, Zn and Mn in kernel. Micronutrients were regularly (significantly or not) increased, being maximized under RPER4 in kernel.
Under the lower compost rate applied, RPER3 and RPER4 showed significant increases in uptake of leaf Fe as compared to RPER1 and RPER2 treatments. Under the higher rate of applied compost, significant Fe increased were resulted in both leaf and kernel of peanut due to increasing the rate of P enrichment. The Fe uptake in peanut kernel (0.461 mg Fe plant-1) under conventional farming was clearly higher than the corresponding mean average value of Fe uptake in peanut kernel 0.442 mg Fe plant-1 under different P treatments and the lower rate of compost applied.
Under the lower rate of compost, the Zn uptake in peanut leaf was significantly increased under each rate of P enrichment as compared with RPER1. Under the higher rate of applied compost, Zn uptake in peanut leaf was significantly increased under each rate of P enrichment, also Zn uptake in peanut kernel was significantly increased under highest two rates of P as compared to RPER1and RPER2. The mean value of Zn uptake in peanut leaf under conventional farming significantly higher than the value of leaf Zn uptake under the higher rate of compost application. The Zn uptake in peanut kernel under conventional farming was clearly lower than both the corresponding mean values of Zn uptake in peanut kernel under different P treatments and both lower and higher rates of compost applied, respectively.
Under the lower rate of applied compost, significant increase was resulted in leaf uptake of peanut Mn due to RPER2. However, the Mn uptake in peanut kernel was significantly increased under RPER4 as compared to RPER1. Under the higher rate of applied compost, significant increase was resulted in leaf uptake of peanut Mn up to RPER2. However, the Mn uptake in peanut kernel was significantly increased under any rate of added P as compared to no added P treatment. The mean values of Mn uptake in peanut leaf and kernel under conventional farming were significantly lower than the corresponding mean values of leaf and kernel Mn uptake under the higher rate of applied compost combined with the different P treatments.
4. The relations between peanut yield and yield components with nutrients content in plant and soil.
Pod yield of peanut was correlated with P and K as well as Mn of kernel, according to the equation:
Pod yield = -1.91 + 0.03 P content of kernel + 6.19 K content of kernel + 0.153 Mn content of kernel (R2 = 74.4 % and R2 adj = 70.6 %).
Multiple linear regression revealed that P and N content of kernel, available N in soil and P content of stem significantly correlated with the kernel yield of peanut according to the equation:
Kernel yield = 3.18 + 24.7 P content of kernel – 2.67 N content of kernel- 0.026 available N in soil + 6.36 P content of stem (R2= 92.2 % and R2adj = 90.5%).
Multiple linear regression revealed that kernel yield, Mn content of leaf and available N of soil significantly correlated with the straw yield of peanut according to the equation:
Straw yield = 0.504 + 2.21 kernel yield – 0.089 Mn content of leaf + 0.042 available N in soil (R2 = 94.9 % and R2adj = 94.1 %).
П. Pepper experiment:
The field experiment aimed to evaluate pepper productivity and nutrients content of pepper under organic farming. Treatments representing all the combinations of compost (10 and 15 ton. fed) and P enrichment rates (0, 26.4, 39.6 and 52.8 kg P fed-1) in a randomized complete block design were replicated three times. Obtained results could be summarized as follows:
1. Response of pepper yield and yield components to compost and P enrichment rate:
The higher compost rate induced all the tested parameters significantly over those obtained under lower organic N rate, except the ascorbic acid content (g kg-1) which was increased insignificantly only. Increasing the rate of applied P induced all of the tested parameters to be maximized under RPER4, except ascorbic acid content (g kg-1) which was maximized under RPER3.
The binary nutrient interaction effect showed that, increasing P fertilization rate under both compost rates increased both yield and yield components. The mostly induced parameters were marketable, unmarketable yields, bell length, diameter and ascorbic content, as well as root dry weight, under the highest rate of applied compost combined with RPER4.
2. Response of nutrients content in pepper to compost and P enrichment rate:
At the maturity stage, compost at the higher rate significantly increased both N and P in pepper stem as well as P and K in pepper root but with insignificant increments for K in stem and N in root. Increasing the rate of compost significantly increased N, P and K content of leaf as well as N content of fruit. The higher rate of applied compost significantly increased all the tested micronutrients (Fe, Mn and Zn in both leaf and fruit.
Increasing the rate of applied P consistently increased N, P and K content of pepper stem and root. Increasing the rate of added P led to an increasing trend in Fe, Zn and Mn contents either in leaf or fruit of pepper.
Regarding the binary nutrients interaction effect, under both the lower and higher compost rate, values of N, P and K content in root, stem, leaf and fruit were increased by increasing P enrichment rate. Under the 1st rate of applied compost, P application up to the RPER3 increased Fe, Zn and Mn content of leaf to maximum levels.
Regarding the comparison between organic and conventional farming systems on nutrients content at maturity stage of pepper plants, N content of stem, root, leaf and fruit increased under conventional (mineral) farming compared to organic farming system. On the other hand the P content in stem, root and leaf of pepper was highest under organic farming than and the conventional (mineral) farming system, but P content in fruit was of higher values under conventional (mineral) farming than those under organic farming system. K content of stem, root, leaf and fruit was highest value under organic farming than under conventional (mineral) farming system. Fe content in leaf and fruit as well as Zn content in leaf increased under organic farming but Zn content only in fruit was increased under conventional (mineral) farming compared to organic farming system.
3. Response of nutrients uptake in pepper to compost and P enrichment rate:
The compost application at the higher rate significantly increased N, P and K uptake in pepper root, stem, leaf and fruit. Increasing the rate of applied P consistently significantly increased root, stem, leaf and fruit of pepper plant uptake of N, P and K, reaching their maximum values by RPER4.
Under both the lower and higher compost rate, values of N, P and K uptake in root, stem, leaf and fruit were increased by increasing P enrichment rate. Macronutrients (N, P and K) uptake of stem, root, leaf and fruit increased under conventional farming compared to organic farming.
The higher rate of applied compost significantly increased all the tested micronutrients (Fe, Mn and Zn) uptake, significantly in both leaf and fruit. Increasing the rate of added P led to an increasing trend in Fe, Zn and Mn uptake either in leaf or fruit of pepper.
Under the 1st rate of applied compost, P application up to RPER4 (52.8 kg P fed-1) increased Fe, Zn and Mn uptake of leaf and fruit to maximum levels. Micronutrients (Fe, Zn and Mn) uptake in leaf and fruit increased under conventional farming compared to organic farming.
4. The relations between pepper yield and yield components with nutrients content in plant and soil.
Unmarketable pepper yield was mainly related to each of K content of bell, ascorbic acid content of bell, P content of leaf and N content of bell, according to the equation:
Unmarketable yield = 0.601- 0.228 K content of bell + 0.023 ascorbic content of bell + 1.180 P content of leaf – 0.405 N content of bell (R2 = 91.5 % and R2 adj = 89.7 %).
Multiple linear regression revealed that marketable yield of pepper is related to stem dry weight, P content of root, Fe content of leaf, available N in soil and height plant according to the equation:
Marketable yield = 2.23 – 0.223 stem dry weight – 34.8 P content of root + 0.017 Fe content of leaf + 0.024 available N content of soil – 0.056 height plant (R2 = 90.8 % and R2adj = 88.2%).