1

Chng 2. CC YU T NH HNG N SINH TRNG CY TRNG

Bi 2. Cc nguyn t dinh dng cn thit cho sinh trng pht trin ca cy trng

Mc tiu - Nhn din 16 nguyn t dinh dng ti cn thit cho tt c cc lai cy trng. - Hiu 13 nguyn t dinh dng khang ti cn thit c cung cp cho cy trng t t. - Nhn bit cc k hiu ha hc v nhu cu tng ti ca cy I. Nguyn t dinh dng ti cn thit. 1. nh ngha. Nguyn t dinh dng ti cn thit l cc nguyn t: - Lin quan trc tip n cc qu trnh trao i cht trong cy, - Cy khng th han thnh chu k sng khi khng c nguyn t ny, v - Cc nguyn t khc khng th th th han tan vai tr ca cc nguyn t ny 2. Cc nguyn t ti cn thit. Bao gm 16 nguyn t ha hc, trong 3 nguyn t Carbon, Hydrogen, Oxygen mc d cy trng hp thu 1 lng ln t khng kh v nc, chim khong 96% cht kh ca cy, nhng thng khng c xem l cht dinh dng tht s-cc nguyn t khung. Chng ta ch ch n 13 nguyn t dinh dng c cung cp t t. Cc nguyn t dinh dng ti cn thit c chia thnh 3 nhm: - Cc nguyn t dinh dng a lng - 3 - Cc nguyn t dinh dng trung lng - 3 - Cc nguyn t dinh dng vi lng - 7 2.1 Cc nguyn t dinh dng a lng. Bao gm Nitrogen N, Phosphorus P, v Potassium K. Cc nguyn t dinh dng a lng l cc cht dinh dng ch yu, chnh ch yu v mt khi lng, nhng khng phi quan trng nht. Nhu cu ca cy vi hm lng tng i cao, trung bnh khong 50-150 kg/ha/v 2.2 Cc nguyn t dinh dng trung lng. Bao gm Calcium Ca Magnesium Mg, v Sulfur S. Hu ht cc loi cy co nhu cu "trung bnh" v hm lng, khong 10-50 kg/ha/v.

2

2.3 Cc nguyn t dinh dng vi lng. Bao gm Boron B, Chlorine Cl, ng Cu, St Fe, Manganese Mn, Molybdenum Mo, Km Zn. Ch , mc d cc nguyn t vi lng cy c nhu cu vi hm lng rt nh, nhng tm quan trng cng nh cc nguyn t a lng. Nhu cu thng

3

3.3. dinh dng: nng dinh dng cao, khi bn thm phn s khng lm tng nng sut*, mc d c th tng nng dinh dng trong cy. 3. 4 tiu th xa x. Khi cy hp thu dinh dng, nu cung cp thm phn bn, hay t c hm lng dinh dng cao, mc d khng c nhu cu nhng cy c th hp thu thm. iu ny c th ci thin cht lng nng sn do nng dinh dng trong cy tng, nh l xanh hn, lng protein caohn 3.5 tha dinh dng: nng dinh dng qu cao lm gim nng sut, hay cht lng nng sn v gy ra s mt cn bng vi cc cht dinh dng khc. V d, tha N c th dn n nhng tc ng xu: mng nc, ng, pht trin nhiu cnh, nhnh v hiu, gim cht lng nng sn (v ng trn bp ci), chng chu su bnh km, s Mt cn bng ion xy ra vi cc ion i khng, nh khi cy hp thu Na cao, s lm gim hp thu K hay Ca; hay khi hp thu K v NH4+ cao dn n thiu Mg. Hin tng tha dinh dng chu nh hng rt ln bi kh nng m ca t. t c kh nng m thp, nu bn nhiu phn, cy d b tha dinh dng. 3.6. ng c : khi nng cc cht dinh dng trong cy qu cao so vi nhu cu cy, c bit vi cc nguyn t vi lng (B v cc cation (Zn, Fe, Mn, Cu)). Lu . - Nu nng dinh dng trong khong rt thiu, hiu qu bn phn s cao nht. - Khi bn phn, nng dinh dng trong cy c th khng cao do s pha lang bi sinh trng. hiu ng Steenberg: hm lng hp thu tng, nhng hm lng cht kh tng ln hn. - Khong dinh dng: tng i rng vi 1 s cht dinh dng (N,K); hp (B) trc khi chuyn qua khong tha/ng c II. Cc nguyn t ha hc c ch. L cc nguyn t ha hc: - C th lm tng nng sut hay phm cht, nhng khng phi l cht ti cn thit. - C th thay th 1 s chc nng trong qu trnh trao i cht ca cc nguyn t ti cn thit (khng thay th tt c). - Mt s cy trng c th tng nng sut, phm cht khi c b sung cc nguyn t ny.

4

Cc nguyn t ny l Sodium (Na), Silicon (Si), Cobalt (Co), Vanadium (Va) Vy tng cc Nguyn t dinh dng ti cn thit & nguyn t c ch khong 20, nhng c hn 60 nguyn t ha hc c tm thy trong cy. Do mt s cht khng phi l nguyn t ti cn thit hay c ch Ngoi ra, mt s cht c cy trng hp thu nhng cha xc nh c tnh cn thit v c ch nh: Aluminum (Al): lm gim nghim trng s pht trin ca r, c th c nng trong cy cao, khi trng trn t chua, phn. c bit i vi cc lai cy khng chu chua. L 1 trong nhng nguyn nhn lm cho ph ca t chua khng cao. C rt nhiu trong t, nhng ch yu nm trong cu trc ca khong st, ch ha tan khi pH thp. Ch (Pb): cao trong t nhim. Cadmium (Cd): cao trong t nhim (bn cng) Mercury (Hg): Phn ln cc nguyn t khng cn thit l kim lai nng. III. S di chuyn ca cc cht dinh dng trong cy. Cc cht dinh dng ti cn thit cng c th phn nhm theo kh nng di chuyn trong cy ca chng. Nhm cht c th di chuyn d dng trong cy nh N, K; nhm khng di chuyn trong cy nh Ca, B. S di chuyn ca cc cht dinh dng trong cy rt c ngha quan trng trong bn phn v ph nhiu ca t. IV. Nhu cu dinh dng ca cy trng Lai, ging cy khc nhau c nhu cu dinh dng khc nhau, s lng cc cht dinh dng ti cn thit nh nhau, nhng nhu cu hm lng khc nhau, v d cy h u cn nhiu Mo hn cc cy trng khc, cy h ci cn nhiu S, to, c chua cn nhiu Ca, 5 nguyn t vi lng ti cn thit cho 1 s cy trng v cc nguyn t c ch khc nh Sodium (Na), cobalt (Co), vanadium (V), nickel (Ni), silicon (Si) c cy trng hp thu vi 1 lng rt khc nhau i vi cc nguyn t khc Cy khng c nhu cu, nhng c th l nhu cu dinh dng i vi ng vt v con ngi (nh Se, Cr). Tm tt.

5

1. Tt c cc nguyn t ha hc cy hp thu khng nht thit l nhng nguyn t ti cn thit cho sinh trng ca cy trng.

2. Cht dinh dng ti cn thit bao gm bt c nguyn t no c cc chc nng trong dinh dng cy trng, d c tnh chuyn bit hay khng.

3. Cc cht dinh dng ti cn thit cho sinh trng cy trng l: C, H, O, N, P, K, Ca, Mg, S, B, Fe, Mn, Cu, Zn, Mo, V Cl.

4. Cc cht c ch: Na, Si, Ni, Co, V cn thit cho 1 s cy trng nht nh. 5. Tr 3 nguyn t C, H, O l cc nguyn t khung, cc nguyn t cn li l

cc nguyn t dinh dng khong. 6. Ty theo nhu cu ca cy trng, cc nguyn t a lng gm: N, P, v K;

cc nguyn t trung lng: Ca, Mg, v S; v cc nguyn t vi lng: Fe, Mn, B, Mo, Cu, Zn, v Cl.

7. S di chuyn v nhu cu cc cht dinh dng khc nhau ty tng cht dinh dng v tng loi cy trng.