1

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

Bi 1. Cc yu t nh hng n sinh trng cy trng. Mc ch. Chng ta s n li cc yu t ny, bi v chng lin quan n yu t gii hn c s dng trong dinh dng cy trng. 1. nh ngha. Sinh trng l mt tin trnh pht trin lin tc ca 1 sinh vt. S sinh trng ca cy trng thng c din t bng trng lng cht kh (tng phn nng sn thu hach, nh ht, qu), chiu cao cy, di, kch thc l, c knh thn S sinh trng ca cy trng hng nm lin quan n thi gian thng c din t l 1 ng cong dng ch S, hay trong 1 ma v sinh trng i vi cy lu nin.

Sinh trng

Thi gian

S sinh trng ca cy trng theo thi gian S sinh trng c tng quan n cc yu t sinh trng. G = f (X1, X2, X3 .....Xn) G = s sinh trng Xi = cc yu t sinh trng 2. Cc yu t nh hng n sinh trng. Cc yu t nh hng n sinh trng cy trng c th chia thnh 2 nhm. 2.1 Yu t di truyn. Tim nng nng sut c quyt nh bi cc gene di truyn ca cy trng. Nng sut cy trng tng trong thi gian qua u c lin quan trc tip n cc ging lai hay cc ging ci thin. Cc c im khc nh cht lng, kh nng khng bnh, chu hn cng do cc yu t di truyn quyt nh. Bp lai, la lai l 1 minh chng ca vic tng nng sut cy trng do yu t di truyn.. Cng ngh di

2

truyn ngy nay tr thnh 1 ngnh quan trng trong vic thay i tim nng nng sut cy trng. Ging v nhu cu dinh dng ca cy- Ging cy cho nng sut 6 tn/ha lun c nhu cu dinh dng cao hn ging cho nng sut 3 tn/ha.. Khi tim nng nng sut cy trng tng, nhu cu dinh dung s tng v ging c nng sut cng cao, hiu qu s dng phn bn cng cao, nht l phn N. Ngi sn xut c th kim sat yu t di truyn bng phng php chn ging thch hp nh ging cho nng sut cao, phm cht tt, tnh chng chu cao. 2.2 Cc yu t mi trng. Yu t mi trng bao gm tt c cc iu kin bn ngai nh hng n sinh trng v pht trin ca 1 sinh vt. i vi cy trng, nhng yu t mi trng quan trng bao gm nhng yu t sau v mi yu t u c th l yu t gii hn sinh trng ca cy. Nhng yu t mi trng khng hat ng c lp, cc yu t ny lun quan h vi nhau, v d - lun c mi quan h hu c gia m v thang t. 2.2.1 Nhit - cng nhit. Cy trng sinh trng bnh thng trong khang nhit 25-40oC. a. nh hng trc tip ca nhit . Nhit nh hng trc tip n cc tin trnh quang hp, h hp, that hi nc, hp thu nc v dinh dng ca cy trng. b. Tc cc tin trnh ny tng khi nhit tng v mc phn ng vi nhit khc nhau i vi tng lai cy trng. V d nh hng ca nhit khc nhau n sinh trng ca cy bng vi v khoai ty (cy a nhit cao v cy a nhit thp). c. Nhit cng nh hng n hat ng ca vi sinh vt trong t. Nhit thp c ch hat ng ca vi khun nitrate ha. pH cng c th gim khi nhit cao, do vi sinh vt hat ng mnh. d. Nhit t cng nh hng n hp thu nc v dinh dng i vi cy trng. 2.2.1 m t. Kh nng cung cp nc sinh trng cy trng b hn ch khi m t qu cao hay qu thp. Chng ta c th kim sat c thng qua phng php ti tiu. m s ci thin c s hp thu dinh dng. Nu m l yu t gii hn, hiu qu s dng phn bn s khng cao. 2.2.3 Nng lng mt tri. Cht lng, cng v thi gian chiu sng l cc ch tiu quan trng ca nh sng nh hng n sinh trng v pht trin ca cy trng. a. Cht lng nh sng l yu t chng ta khng kim sat c trn ng rung. b. Cng ang sng l tnh cht quan trng do tin trnh quang hp c lin quan mt thit vi cng nh sng. Bp c dng l thng s hp thu nhiu nh sng hn dng l xe ngang.

3

c. Thi gian chiu sng Quang k - Cy trng c lin quan n di ngy - Cy ngy di Ch ra hoa khi di ngy di hn 12 gi. Cy ng cc. - Cy ngy ngn - Ch ra hoa khi di ngy ngn hn 12 gi. - Cy trung tnh vi quang k- ra hoa trong khang di ngy rng. C chua, bng vi Do nh hng ca quang k nn 1 s lai cy trng c th khng ra hoa trn 1 s vng. Hoa cc, thanh long c th ra hoa bng phng php kim sat quang k. 2.2.4 Thnh phn ca kh quyn. CO2 chim 0.03 % th tch khng kh. Quang tng hp bin i CO2 thnh cht hu c trong cy. CO2 s c tr li kh quyn bi tin trnh h hp hay phn gii cht hu c. Trong 1 iu kin no , nu nng CO2 gim c th s l yu t gii hn sinh trng ca cy trng. Khi tng nng c th nng sut cy trng tng nh cc nghin cu trn la, c chua, da chut, hoa, khoai ty Cht lng khng kh. Nu khng kh b nhim cao, c th gy ng c cho cy nh sulfur dioxide, carbon monoxide, hydrofluoric acid 2.2.5 thang kh ca t. t b nn cht vi dung trng cao, cu trc km thng l t c thang kh km. rng ca t c chim gi bi khng kh v nc nn nc v khng kh trong t c t l nghch. t that nc tt, thng hm lng oxy ha tan khng l yu t gii hn sinh trng ca cy. Cy trng khc nhau, mc nhy cm vi hm lng oxy trong t khc nhau, v d cy la nc v cy thuc l. 2.2.6 Phn ng ca t. pH t nh hng n kh nng hu dng ca 1 s cht dinh dng nh kh nng hu dng ca P thp trn t chua, Al ha tan mnh trn t chua c th gy c cho cy. Mt s vi sinh vt gy bnh ca chu nh hng bi pH, v d bnh gh v khoai ty c th kim sat c khi pH

4

dng vi lng ng, manganese, km, boron, molybdenum, chlorine, st. Cc nguyn t c ch cho 1 s cy trng nh cobalt, vanadium, sodium, silicon. 2.2.9 Cc cht c ch, gy c cho cy trng. Cc cht dinh dng ca cy trng khi tn ti vi nng cao u c th c ch sinh trng hay gy c cho cy. Cc cht khc bao gm aluminum, nickel, ch thng i vi bn cng, cht thi cng nghip, hm m, cc hp cht hu c nh phenols, du. 3. Cc yu t gii hn nng sut. Bt k yu t no, c th l yu t di truyn hay yu t mi trng, yu t nc, nh sng, dinh dng. cng c th gii hn nng sut cy trng. - nh lut ti thiu (Liebig, 1860s). 1 hay nhiu cht dinh dng trong t c th c nng cao (ti a), v cng c th c nng rt thp (ti thiu). Vi cc cht dinh dng ti thiu, c th l Ca, Mg, K, hay bt k cht dinh dng no khc, nng sut s tng quan trc tip vi cc cht dinh dng ti thiu ny. - Yu t ti thiu kim sot nng sut. V d, yu t ti thiu ca t l vi, nng sut cy trng s khng tng ngay c khi chng ta bn cc lai phn bn khc tng gp 100 ln** nu khng bn vi. nh lut trn pht biu cho cc cht dinh dng, nhng c th p dng cho bt k yu t sinh trng no khc. S sinh trng ca cy trng b gii hn, khi cht dinh dng hin din vi hm lng gii hn (ti thiu), bt k cc cht dinh dng khc c hm lng v kh nng cung cp cho cy y hay d tha. Mc tiu ca nh sn xut l phi nhn din tt c cc yu t gii hn lm gim nng sut cy trng. Tm tt yu t gii hn nng sut. - Nu c nhiu yu t gii hn th yu t gii hn cao nht quyt nh tim nng nng sut. - Ch khi no gii quyt c yu t gii hn ny, nng sut cy trng mi c ci thin. - i vi cc cht dinh dng. Cht gii hn cao nht l cht c hm lung tng i thp nht so vi yu cu ca cy trng (ngng dinh dng). Tm tt

1. S sinh trng ca cy trng ph thuc vo thi gian, cc c tnh di truyn, cc yu t mi trng. Chn ging thch hp s dng c hiu qu cc cht dinh dng trong t.

5

2. Cc yu t mi trng c nh hng tng hp n sinh trng v s phn ng ca cy trng i vi vic cung cp cc cht dinh dng.

3. S sinh trng ca cy trng hng nm, 1 ma v ca cy ln nm c dng ch S. Cy trng phn ng vi cc iu kin mi trng k c phn bn cng c dng nh trn. Khi hm lng dinh dng tng, s sinh trng tng, nhng mc tng trn 1 n v dinh dng gim.

4. Yu t gii hn cao nht l yu t kim sot nng sut. Ch khi no nhn din v gii quyt yu t gii hn ny, nng sut s tng.