Effect of soil-applied CaC₂ on gas exchange characters, nitrogen metabolism and fruit yield in cucumber (Cucumis sativus)

Figures & data

Table 1. Main effects of the addition of various concentrations of nitrogen and paint-coated calcium carbide (PCC) on a range of morphophysiological characteristics in cucumber (Cucumis sativus).

Parameter	N concentration			PCC concentration
	0	30	60	0	20	30
	(mg kg^−1 soil)
Vine length (cm)	133 c	161 b	179 a	167 a	160 b	145 c
Leaf area (dm^2)	79 c	102 b	116 a	93 c	99 b	105 a
Number of primary branches	5 c	6 b	7 a	5 c	6 b	6.4 a
Days to first female flower	42 a	39 b	36 c	43 a	39 b	35 c
Days to fruit setting	15 a	15 b	13 c	16 a	14 b	13 c
Number of fruit per plant	12 c	15 b	18 a	13 c	15 b	17 a
Fruit yield (t ha^−1)	17 c	23 b	29 a	19 c	23 b	27 a
Photosynthetic rate (µmol m^−2 s^−1)	12 c	15 b	19 a	12 c	15 b	18 a
Stomatal conductance (mmol m^−2 s^−1)	306 c	344 b	407 a	294c	361 b	401 a
Intercellular CO2 (µmol mol^−1)	231 c	259 b	280 a	226 c	260 b	284 a
Carboxylation efficiency (%)	5 c	6 b	7 a	5.1 c	5.8 b	6.4 a
Photosynthetic WUE (µmol mol^−1)	38 c	44 b	46 a	40 c	43 b	46 a
Ethylene production (nL g^−1h^−1)	0.58 a	0.43 b	0.33 c	0.30 c	0.45 b	0.55 a
Nitrogen use efficiency (kg/kg)	–	5.4 a	4.9 a	2.9 c	5.2 b	7.4 a
NRA (nmol NO2·g FW^−1·h^−1)	336 c	448 b	555 a	423 c	447 b	469 a

Note: WUE, water use efficiency; NRA, nitrate reductase activity; FW, fresh weight.

Means within a row that are followed by the same letter(s) do not differ significantly at p ≤ .05 at different levels of nitrogen and PCC.

Table 2. Interactive effects of nitrogen and paint-coated calcium carbide (PCC) applications on the growth and fruit yield of cucumber (Cucumis sativus).

N concentration	PCC concentration	Vine length	Leaf area	Number of primary branches	Days to first female flower initiation	Days to fruit setting	Number of fruit per plant	Fruit yield
(mg kg^−1 soil)		(cm)	(dm^2)					(t ha^−1)
0	0	141 a	75 e	4.5 h	45 a	17 a	11 h	15 g
	20	136 de	79 e	5.1 g	42 b	15 b	12 g	18 f
	30	124 e	83 e	5.6 ef	39 d	13 d	13 f	20 e
30	0	171 bc	94 d	5.3 fg	43 ab	17 a	13 f	20 e
	20	164 c	103 c	5.9 de	40 cd	14 c	15 e	24 d
	30	147 d	108 bc	6.5 bc	34 e	13 de	17 c	27 c
60	0	190 a	110 bc	6.2 cd	41 bc	14 c	15 d	24 d
	20	181 ab	116 ab	6.7 b	36 e	12 e	17 b	30 b
	30	165 c	122 a	7.2 a	31 f	12 e	20 a	36 a
LSD value (p ≤ .05)		12.2	8.3	0.45	2.2	0.79	0.66	1.7

Note: LSD, least significant difference test.

Means within a column that are followed by the same letter(s) do not differ significantly at p ≤ .05.

Figure 1. Linear regression between the photosynthetic rate (Pn) and intercellular CO₂ concentration (Ci), which was used to calculate the carboxylation efficiency of cucumber (Cucumis sativus) plants.

Table 3. Interactive effects of nitrogen and paint-coated calcium carbide (PCC) applications on the physiological parameters of cucumber (Cucumis sativus).

N concentration	PCC concentration	Photosynthetic rate	Stomatal conductance	Intercellular CO2 concentration	Photosynthetic water use efficiency	Carboxylation efficiency
(mg kg^−1 soil)		(µmol m^−2 s^−1)	(mmol m^−2 s^−1)	(µmol mol^−1)		(%)
0	0	9 f	267 e	210 f	36 e	4.4 f
	20	12 e	313 d	233 de	37 e	5.0 e
	30	14 d	341 c	251 cd	41 d	5.4 d
30	0	12 e	283 e	228 ef	41 d	5.1 de
	20	16 c	353 c	268 bc	45 bc	5.9 c
	30	18 b	395 b	281 b	46 b	6.5 b
60	0	14 d	335 cd	240 de	43 cd	5.9 c
	20	18 b	417 b	280 b	46 b	6.6 b
	30	23 a	468 a	319 a	50 a	7.2 a
LSD value (p ≤ .05)		1.19	27.4	19.8	3.31	0.44

Note: LSD, least significant difference test.

Means within a column that are followed by the same letter(s) do not differ significantly at p ≤ .05.

Table 4. Interactive effects of nitrogen and paint-coated calcium carbide (PCC) applications on ethylene production, nitrogen use efficiency (NUE), and nitrate reductase (NR) activity in cucumber (Cucumis sativus).

N concentration	PCC concentration	Ethylene production	NUE	NR activity
(mg kg^−1 soil)		(nL g^−1 h^−1)	(kg kg^−1)	(nmol NO2·g FW^−1·h^−1)
0	0	0.41 d	–	309 g
	20	0.62 b	–	335 f
	30	0.72 a	–	364 e
30	0	0.34 e	2.87 d	425 d
	20	0.43 d	5.43 c	449 cd
	30	0.53 c	7.90 a	470 c
60	0	0.27 f	3.08 d	534 b
	20	0.31 e	4.87 c	558 ab
	30	0.41 d	6.91 b	573 a
LSD value (p ≤ .05)		0.04	0.87	25.31

Note: FW, fresh weight; LSD, least significant difference test.

Means within a column that are followed by the same letter(s) do not differ significantly at p ≤ .05.